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Seq	Timestamp	Type	Name	Duration
0/0	2026/09/13 19:51	flow	patch-triage	3m Args: null Results: { "EnableConfigs": [ "FUSE_FS", "NET_9P", "9P_FS" ], "FocusSymbols": [ "lookup_open", "may_o_create", "atomic_open", "may_create_in_sticky", "vfs_mkdir", "vfs_create", "fuse_atomic_open" ], "KMSANReasoning": "The patch series adds support for creating directories via open/openat using the `O_CREAT \| O_DIRECTORY` flag combination. The changes encompass:\n1. Validating and setting flags/modes in `build_open_flags()` (`fs/open.c`) to permit `O_CREAT \| O_DIRECTORY` with `S_IFDIR`.\n2. Refactoring VFS directory creation helpers (`vfs_mkdir_no_perm`) and directory creation permission checks (`may_o_create`, `may_create_in_sticky`) in `fs/namei.c`.\n3. Updating `atomic_open` implementations across various filesystems (9p, ceph, fuse, gfs2, nfs, smb, vboxsf) to strip `O_CREAT` when `O_DIRECTORY` is specified and fall back gracefully.\n\nNone of the changes allocate uninitialized heap/stack memory, copy kernel structures to user space, alter length/bounds checks on buffers, or read uninitialized struct fields or variables. All local variables (including `struct delegated_inode`) are zero-initialized. Potential issues arising from these changes (such as dentry/inode reference counting bugs, use-after-free, locking order inconsistencies, or NULL pointer dereferences) are fully covered by standard KASAN and LOCKDEP detectors. Therefore, a dedicated KMSAN fuzzing session is not justified.", "NeedsKMSAN": false, "Reasoning": "The patch introduces support for creating directories via openat() using O_CREAT \| O_DIRECTORY, refactoring core VFS path lookup, permission checks, directory creation helpers, and inode locking, as well as updating atomic_open implementations across multiple filesystems (including FUSE and 9p). These are substantial logic changes in core VFS and reachable syscall handlers, including new runtime assertions (WARN_ON_ONCE in may_o_create) and security checks, which warrant fuzzing.", "WorthFuzzing": true }
1/1	2026/09/13 19:51	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 3460f086b4bc3a2056c482324556c2230583a0f9\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Sun Sep 13 19:51:27 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c\nindex 3829554ca3692..dd810904ff6c0 100644\n--- a/fs/9p/vfs_inode.c\n+++ b/fs/9p/vfs_inode.c\n@@ -776,6 +776,11 @@ v9fs_vfs_atomic_open(struct inode dir, struct dentry dentry,\n \tstruct inode inode;\n \tint p9_omode;\n \n+\tif (O_IS_MKDIR(flags)) {\n+\t\tflags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \tif (d_in_lookup(dentry)) {\n \t\tstruct dentry res = v9fs_vfs_lookup(dir, dentry, 0);\n \t\tif (res \|\| d_really_is_positive(dentry))\ndiff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c\nindex 116b29e95f21e..9308184aee611 100644\n--- a/fs/9p/vfs_inode_dotl.c\n+++ b/fs/9p/vfs_inode_dotl.c\n@@ -238,6 +238,11 @@ v9fs_vfs_atomic_open_dotl(struct inode dir, struct dentry dentry,\n \tstruct v9fs_session_info v9ses;\n \tstruct posix_acl pacl = NULL, dacl = NULL;\n \n+\tif (O_IS_MKDIR(flags)) {\n+\t\tflags \u0026= ~O_CREAT;\n+\t\tomode = 0;\n+\t}\n+\n \tif (d_in_lookup(dentry)) {\n \t\tstruct dentry res = v9fs_vfs_lookup(dir, dentry, 0);\n \t\tif (res \|\| d_really_is_positive(dentry))\ndiff --git a/fs/ceph/file.c b/fs/ceph/file.c\nindex bd3e3f5c269e8..9235143edd9a8 100644\n--- a/fs/ceph/file.c\n+++ b/fs/ceph/file.c\n@@ -812,6 +812,11 @@ int ceph_atomic_open(struct inode dir, struct dentry dentry,\n \t dir, ceph_vinop(dir), dentry, dentry,\n \t d_unhashed(dentry) ? \"unhashed\" : \"hashed\", flags, mode);\n \n+\tif (O_IS_MKDIR(flags)) {\n+\t\tflags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \tif (dentry-\u003ed_name.len \u003e NAME_MAX)\n \t\treturn -ENAMETOOLONG;\n \ndiff --git a/fs/fuse/dir.c b/fs/fuse/dir.c\nindex e49b4e874b15f..a3e7daba61dcb 100644\n--- a/fs/fuse/dir.c\n+++ b/fs/fuse/dir.c\n@@ -944,6 +944,11 @@ static int fuse_atomic_open(struct inode dir, struct dentry entry,\n \tstruct mnt_idmap idmap = file_mnt_idmap(file);\n \tstruct fuse_conn fc = get_fuse_conn(dir);\n \n+\tif (O_IS_MKDIR(flags)) {\n+\t\tflags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \tif (fuse_is_bad(dir))\n \t\treturn -EIO;\n \ndiff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c\nindex f361876c55833..69e100a68e2c0 100644\n--- a/fs/gfs2/inode.c\n+++ b/fs/gfs2/inode.c\n@@ -1386,6 +1386,11 @@ static int gfs2_atomic_open(struct inode dir, struct dentry dentry,\n {\n \tbool excl = !!(flags \u0026 O_EXCL);\n \n+\tif (O_IS_MKDIR(flags)) {\n+\t\tflags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \tif (d_in_lookup(dentry)) {\n \t\tstruct dentry d = __gfs2_lookup(dir, dentry, file);\n \t\tif (file-\u003ef_mode \u0026 FMODE_OPENED) {\ndiff --git a/fs/namei.c b/fs/namei.c\nindex 20a6534ea3eff..fce3aaa373658 100644\n--- a/fs/namei.c\n+++ b/fs/namei.c\n@@ -1382,13 +1382,13 @@ int may_linkat(struct mnt_idmap idmap, const struct path link)\n \n /\n may_create_in_sticky - Check whether an O_CREAT open in a sticky directory\n- \t\t\t should be allowed, or not, on files that already\n- \t\t\t exist.\n+ \t\t\t should be allowed, or not, on files/directories that\n+ \t\t\t already exist.\n * @idmap: idmap of the mount the inode was found from\n * @nd: nameidata pathwalk data\n * @inode: the inode of the file to open\n \n- Block an O_CREAT open of a FIFO (or a regular file) when:\n+ * Block an O_CREAT open of a FIFO (or a regular file/directory) when:\n * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled\n * - the file already exists\n * - we are in a sticky directory\n@@ -1416,6 +1416,14 @@ static int may_create_in_sticky(struct mnt_idmap idmap, struct nameidata nd,\n \tif (likely(!(dir_mode \u0026 S_ISVTX)))\n \t\treturn 0;\n \n+\t/\n+\t There is no separate sysctl for directory creation in sticky\n+\t * folders. Therefore, for the S_ISDIR case, disabling\n+\t * sysctl_protected_regular is not enough to allow creating a\n+\t * directory in a sticky folder, because that may surprise users\n+\t * not expecting that O_CREAT\|O_DIRECTORY is possible on newer\n+\t * kernels.\n+\t /\n \tif (S_ISREG(inode-\u003ei_mode) \u0026\u0026 !sysctl_protected_regular)\n \t\treturn 0;\n \n@@ -1447,6 +1455,12 @@ static int may_create_in_sticky(struct mnt_idmap idmap, struct nameidata nd,\n \t\t\t\t\t \"sticky_create_regular\");\n \t\t\treturn -EACCES;\n \t\t}\n+\n+\t\tif (S_ISDIR(inode-\u003ei_mode)) {\n+\t\t\taudit_log_path_denied(AUDIT_ANOM_CREAT,\n+\t\t\t\t\t \"sticky_create_dir\");\n+\t\t\treturn -EACCES;\n+\t\t}\n \t}\n \n \treturn 0;\n@@ -2781,9 +2795,16 @@ static const char path_init(struct nameidata nd, unsigned flags)\n \treturn s;\n }\n \n+static inline bool trailing_slashes(const struct qstr last)\n+{\n+\t/* last-\u003elen is set by hash_name() to the length of the current\n+\t * component -\u003ename, terminating with '/' or a NUL character. /\n+\treturn (bool)last-\u003ename[last-\u003elen];\n+}\n+\n static inline const char lookup_last(struct nameidata nd)\n {\n-\tif (nd-\u003elast_type == LAST_NORM \u0026\u0026 nd-\u003elast.name[nd-\u003elast.len])\n+\tif (nd-\u003elast_type == LAST_NORM \u0026\u0026 trailing_slashes(\u0026nd-\u003elast))\n \t\tnd-\u003eflags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY;\n \n \treturn walk_component(nd, WALK_TRAILING);\n@@ -4159,6 +4180,24 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap idmap,\n \treturn mode;\n }\n \n+static inline\n+int vfs_create_no_perm(struct mnt_idmap idmap, struct dentry dentry,\n+\t\t umode_t mode, struct delegated_inode di)\n+{\n+\tstruct inode dir = d_inode(dentry-\u003ed_parent);\n+\tint error;\n+\n+\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di);\n+\tif (error)\n+\t\treturn error;\n+\n+\terror = dir-\u003ei_op-\u003ecreate(idmap, dir, dentry, mode);\n+\tif (!error)\n+\t\tfsnotify_create(dir, dentry);\n+\n+\treturn error;\n+}\n+\n /*\n vfs_create - create new file\n * @idmap:\tidmap of the mount the inode was found from\n@@ -4185,19 +4224,14 @@ int vfs_create(struct mnt_idmap idmap, struct dentry dentry, umode_t mode,\n \t\treturn error;\n \n \tif (!dir-\u003ei_op-\u003ecreate)\n-\t\treturn -EACCES;\t/* shouldn't it be ENOSYS? /\n+\t\treturn -EOPNOTSUPP;\n \n \tmode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);\n \terror = security_inode_create(dir, dentry, mode);\n \tif (error)\n \t\treturn error;\n-\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di);\n-\tif (error)\n-\t\treturn error;\n-\terror = dir-\u003ei_op-\u003ecreate(idmap, dir, dentry, mode);\n-\tif (!error)\n-\t\tfsnotify_create(dir, dentry);\n-\treturn error;\n+\n+\treturn vfs_create_no_perm(idmap, dentry, mode, di);\n }\n EXPORT_SYMBOL(vfs_create);\n \n@@ -4314,21 +4348,43 @@ static inline int open_to_namei_flags(int flag)\n \n static int may_o_create(struct mnt_idmap idmap,\n \t\t\tconst struct path dir, struct dentry dentry,\n-\t\t\tumode_t mode)\n+\t\t\tint open_flag, umode_t mode)\n {\n-\tint error = security_path_mknod(dir, dentry, mode, 0);\n+\tstruct inode dir_inode = dir-\u003edentry-\u003ed_inode;\n+\tbool create_dir = O_IS_MKDIR(open_flag);\n+\tint error;\n+\n+\tWARN_ON_ONCE(create_dir \u0026\u0026 !(mode \u0026 S_IFDIR));\n+\n+\tif (create_dir)\n+\t\terror = security_path_mkdir(dir, dentry, mode);\n+\telse\n+\t\terror = security_path_mknod(dir, dentry, mode, 0);\n \tif (error)\n \t\treturn error;\n \n \tif (!fsuidgid_has_mapping(dir-\u003edentry-\u003ed_sb, idmap))\n \t\treturn -EOVERFLOW;\n \n-\terror = inode_permission(idmap, dir-\u003edentry-\u003ed_inode,\n-\t\t\t\t MAY_WRITE \| MAY_EXEC);\n+\terror = inode_permission(idmap, dir_inode, MAY_WRITE \| MAY_EXEC);\n \tif (error)\n \t\treturn error;\n \n-\treturn security_inode_create(dir-\u003edentry-\u003ed_inode, dentry, mode);\n+\tif (create_dir)\n+\t\terror = security_inode_mkdir(dir_inode, dentry, mode);\n+\telse\n+\t\terror = security_inode_create(dir_inode, dentry, mode);\n+\n+\treturn error;\n+}\n+\n+static inline umode_t o_create_mode(struct mnt_idmap idmap,\n+\t\tconst struct inode dir, int open_flag, umode_t mode)\n+{\n+\tif (O_IS_MKDIR(open_flag))\n+\t\treturn vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO \| S_ISVTX, S_IFDIR);\n+\telse\n+\t\treturn vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);\n }\n \n /\n@@ -4364,8 +4420,9 @@ static struct dentry atomic_open(const struct path path, struct dentry dentry\n \n \tfile-\u003e__f_path.dentry = DENTRY_NOT_SET;\n \tfile-\u003e__f_path.mnt = path-\u003emnt;\n+\n \terror = dir_inode-\u003ei_op-\u003eatomic_open(dir_inode, dentry, file,\n-\t\t\t\t open_to_namei_flags(open_flag), mode);\n+\t\t\t\t\t open_to_namei_flags(open_flag), mode);\n \td_lookup_done(dentry);\n \n \tif (!error) {\n@@ -4407,13 +4464,43 @@ static struct dentry atomic_open(const struct path path, struct dentry dentry\n \t\t\t /\n \t\t\taudit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);\n \t\t\terror = create_error;\n+\t\t} else if (O_IS_MKDIR(open_flag) \u0026\u0026 error == -ENOENT) {\n+\t\t\t/\n+\t\t\t If the underlying filesystem does not implement\n+\t\t\t * O_CREAT\|O_DIRECTORY, it strips the O_CREAT bit and\n+\t\t\t * continues as a lookup. We can't simply return\n+\t\t\t * -EOPNOTSUPP from unsupported -\u003eatomic_open()\n+\t\t\t * implementations because the dentry might be in the\n+\t\t\t * dcache. In that case, lookup_open() returns before\n+\t\t\t * reaching -\u003eatomic_open(), and hence whether you get\n+\t\t\t * -EOPNOTSUPP on O_CREAT\|O_DIRECTORY would not only\n+\t\t\t * depend on the underlying filesystem, but also on\n+\t\t\t * the state of the dcache. Still, we must make an\n+\t\t\t * effort to differentiate a regular -ENOENT from the\n+\t\t\t * unsupported O_CREAT\|O_DIRECTORY case.\n+\t\t\t /\n+\t\t\terror = -EOPNOTSUPP;\n \t\t}\n \t\tdput(dentry);\n \t\tdentry = ERR_PTR(error);\n+\t} else {\n+\t\tif (file-\u003ef_mode \u0026 FMODE_CREATED) {\n+\t\t\tif (d_is_dir(dentry))\n+\t\t\t\tfsnotify_mkdir(dir_inode, dentry);\n+\t\t\telse\n+\t\t\t\tfsnotify_create(dir_inode, dentry);\n+\t\t}\n+\t\tif (file-\u003ef_mode \u0026 FMODE_OPENED)\n+\t\t\tfsnotify_open(file);\n \t}\n+\n+\n \treturn dentry;\n }\n \n+static inline\n+struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry ,\n+\t\t\t\t umode_t, struct delegated_inode );\n /\n Look up and maybe create and open the last component.\n \n@@ -4435,6 +4522,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file,\n \tstruct mnt_idmap idmap;\n \tstruct dentry dir = nd-\u003epath.dentry;\n \tstruct inode dir_inode = dir-\u003ed_inode;\n+\tbool create_dir = O_IS_MKDIR(op-\u003eopen_flag);\n \tint open_flag;\n \tstruct dentry dentry;\n \tint error, create_error;\n@@ -4455,7 +4543,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file,\n \t\t /\n \t}\n \tif (open_flag \u0026 O_CREAT)\n-\t\tinode_lock(dir_inode);\n+\t\tinode_lock_nested(dir_inode, I_MUTEX_PARENT);\n \telse\n \t\tinode_lock_shared(dir_inode);\n \n@@ -4507,12 +4595,17 @@ static struct dentry lookup_open(struct nameidata nd, struct file file,\n \tif (open_flag \u0026 O_CREAT) {\n \t\tif (open_flag \u0026 O_EXCL)\n \t\t\topen_flag \u0026= ~O_TRUNC;\n-\t\tmode = vfs_prepare_mode(idmap, dir_inode, mode, mode, mode);\n+\t\tmode = o_create_mode(idmap, dir_inode, open_flag, mode);\n \t\tif (likely(got_write))\n \t\t\tcreate_error = may_o_create(idmap, \u0026nd-\u003epath,\n-\t\t\t\t\t\t dentry, mode);\n+\t\t\t\t\t\t dentry, open_flag, mode);\n \t\telse\n \t\t\tcreate_error = -EROFS;\n+\t\t/ Refuse to create a directory through a dangling (trailing)\n+\t\t * symlink. For regular files this has been allowed historically\n+\t\t * on O_CREAT without O_EXCL. /\n+\t\tif (unlikely(nd-\u003edepth) \u0026\u0026 create_dir \u0026\u0026 !create_error)\n+\t\t\tcreate_error = -EEXIST;\n \t}\n \tif (create_error)\n \t\topen_flag \u0026= ~O_CREAT;\n@@ -4537,6 +4630,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file,\n \t\t\tdentry = res;\n \t\t}\n \t}\n+\n \tif (dentry-\u003ed_inode \|\| !(op-\u003eopen_flag \u0026 O_CREAT)) {\n \t\t/\n \t\t No need to create a file. If lookup returned a positive\n@@ -4554,26 +4648,26 @@ static struct dentry lookup_open(struct nameidata nd, struct file file,\n \t\tgoto out_dput;\n \t}\n \n-\terror = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE, \u0026delegated_inode);\n-\tif (error)\n-\t\tgoto out_dput;\n-\n-\tfile-\u003ef_mode \|= FMODE_CREATED;\n-\tif (!dir_inode-\u003ei_op-\u003ecreate) {\n-\t\terror = -EACCES;\n+\tif ((create_dir \u0026\u0026 !dir_inode-\u003ei_op-\u003emkdir)\n+\t\t\|\| (!create_dir \u0026\u0026 !dir_inode-\u003ei_op-\u003ecreate)) {\n+\t\terror = -EOPNOTSUPP;\n \t\tgoto out_dput;\n \t}\n \n-\terror = dir_inode-\u003ei_op-\u003ecreate(idmap, dir_inode, dentry, mode);\n+\tif (create_dir) {\n+\t\tstruct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode,\n+\t\t\t\t\t\t \u0026delegated_inode);\n+\t\terror = PTR_ERR_OR_ZERO(res);\n+\t\tif (!error)\n+\t\t\tdentry = res;\n+\t} else {\n+\t\terror = vfs_create_no_perm(idmap, dentry, mode, \u0026delegated_inode);\n+\t}\n \tif (error)\n \t\tgoto out_dput;\n+\n+\tfile-\u003ef_mode \|= FMODE_CREATED;\n out:\n-\tif (!IS_ERR(dentry)) {\n-\t\tif (file-\u003ef_mode \u0026 FMODE_CREATED)\n-\t\t\tfsnotify_create(dir_inode, dentry);\n-\t\tif (file-\u003ef_mode \u0026 FMODE_OPENED)\n-\t\t\tfsnotify_open(file);\n-\t}\n \tif ((open_flag \u0026 O_CREAT) \|\| create_error)\n \t\tinode_unlock(dir_inode);\n \telse\n@@ -4695,17 +4789,12 @@ struct file vfs_lookup_open(struct path parent, struct qstr last,\n }\n EXPORT_SYMBOL_FOR_MODULES(vfs_lookup_open, \"nfsd\");\n \n-static inline bool trailing_slashes(struct nameidata nd)\n-{\n-\treturn (bool)nd-\u003elast.name[nd-\u003elast.len];\n-}\n-\n static struct dentry lookup_fast_for_open(struct nameidata nd, int open_flag)\n {\n \tstruct dentry dentry;\n \n \tif (open_flag \u0026 O_CREAT) {\n-\t\tif (trailing_slashes(nd))\n+\t\tif (trailing_slashes(\u0026nd-\u003elast) \u0026\u0026 !(open_flag \u0026 O_DIRECTORY))\n \t\t\treturn ERR_PTR(-EISDIR);\n \n \t\t/ Don't bother on an O_EXCL create /\n@@ -4713,7 +4802,7 @@ static struct dentry lookup_fast_for_open(struct nameidata nd, int open_flag)\n \t\t\treturn NULL;\n \t}\n \n-\tif (trailing_slashes(nd))\n+\tif (trailing_slashes(\u0026nd-\u003elast))\n \t\tnd-\u003eflags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY;\n \n \tdentry = lookup_fast(nd);\n@@ -4806,8 +4895,9 @@ static int do_open(struct nameidata nd,\n \tif (open_flag \u0026 O_CREAT) {\n \t\tif ((open_flag \u0026 O_EXCL) \u0026\u0026 !(file-\u003ef_mode \u0026 FMODE_CREATED))\n \t\t\treturn -EEXIST;\n-\t\tif (d_is_dir(nd-\u003epath.dentry))\n+\t\tif (!(open_flag \u0026 O_DIRECTORY) \u0026\u0026 d_is_dir(nd-\u003epath.dentry))\n \t\t\treturn -EISDIR;\n+\n \t\terror = may_create_in_sticky(idmap, nd,\n \t\t\t\t\t d_backing_inode(nd-\u003epath.dentry));\n \t\tif (unlikely(error))\n@@ -5087,7 +5177,7 @@ static struct dentry filename_create(int dfd, struct filename name,\n \t * Do the final lookup. Suppress 'create' if there is a trailing\n \t * '/', and a directory wasn't requested.\n \t /\n-\tif (last.name[last.len] \u0026\u0026 !want_dir)\n+\tif (trailing_slashes(\u0026last) \u0026\u0026 !want_dir)\n \t\tcreate_flags \u0026= ~LOOKUP_CREATE;\n \tdentry = start_dirop(path-\u003edentry, \u0026last, reval_flag \| create_flags);\n \tif (IS_ERR(dentry))\n@@ -5145,7 +5235,7 @@ inline struct dentry start_creating_user_path(\n EXPORT_SYMBOL(start_creating_user_path);\n \n /*\n- dentry_create - Create and open a file\n+ * dentry_create - Create and open a regular file\n * @path: path to create\n * @flags: O\\_ flags\n * @mode: mode bits for new file\n@@ -5182,7 +5272,7 @@ struct file dentry_create(struct path path, int flags, umode_t mode,\n \t\tpath-\u003edentry = dir;\n \t\tmode = vfs_prepare_mode(idmap, dir_inode, mode, S_IALLUGO, S_IFREG);\n \n-\t\tcreate_error = may_o_create(idmap, path, dentry, mode);\n+\t\tcreate_error = may_o_create(idmap, path, dentry, flags, mode);\n \t\tif (create_error)\n \t\t\tflags \u0026= ~O_CREAT;\n \n@@ -5198,13 +5288,6 @@ struct file dentry_create(struct path path, int flags, umode_t mode,\n \t\t\t/* Drop the extra reference /\n \t\t\tdput(orig_dentry);\n \n-\t\tif (!error) {\n-\t\t\tif (file-\u003ef_mode \u0026 FMODE_CREATED)\n-\t\t\t\tfsnotify_create(dir-\u003ed_inode, dentry);\n-\t\t\tif (file-\u003ef_mode \u0026 FMODE_OPENED)\n-\t\t\t\tfsnotify_open(file);\n-\t\t}\n-\n \t\tpath-\u003edentry = dentry;\n \n \t} else {\n@@ -5356,6 +5439,33 @@ SYSCALL_DEFINE3(mknod, const char __user , filename, umode_t, mode, unsigned, d\n \treturn filename_mknodat(AT_FDCWD, name, mode, dev);\n }\n \n+static inline\n+struct dentry vfs_mkdir_no_perm(struct mnt_idmap idmap, struct inode dir,\n+\t\t\t\t struct dentry dentry, umode_t mode,\n+\t\t\t\t struct delegated_inode di)\n+{\n+\tunsigned max_links = dir-\u003ei_sb-\u003es_max_links;\n+\tstruct dentry de;\n+\tint error;\n+\n+\tif (max_links \u0026\u0026 dir-\u003ei_nlink \u003e= max_links)\n+\t\treturn ERR_PTR(-EMLINK);\n+\n+\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di);\n+\tif (error)\n+\t\treturn ERR_PTR(error);\n+\n+\tde = dir-\u003ei_op-\u003emkdir(idmap, dir, dentry, mode);\n+\tif (IS_ERR(de))\n+\t\treturn de;\n+\tif (de) {\n+\t\tdput(dentry);\n+\t\tdentry = de;\n+\t}\n+\tfsnotify_mkdir(dir, dentry);\n+\treturn dentry;\n+}\n+\n /*\n vfs_mkdir - create directory returning correct dentry if possible\n * @idmap:\t\tidmap of the mount the inode was found from\n@@ -5383,14 +5493,13 @@ struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir,\n \t\t\t struct delegated_inode delegated_inode)\n {\n \tint error;\n-\tunsigned max_links = dir-\u003ei_sb-\u003es_max_links;\n \tstruct dentry de;\n \n \terror = may_create_dentry(idmap, dir, dentry);\n \tif (error)\n \t\tgoto err;\n \n-\terror = -EPERM;\n+\terror = -EOPNOTSUPP;\n \tif (!dir-\u003ei_op-\u003emkdir)\n \t\tgoto err;\n \n@@ -5399,24 +5508,12 @@ struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir,\n \tif (error)\n \t\tgoto err;\n \n-\terror = -EMLINK;\n-\tif (max_links \u0026\u0026 dir-\u003ei_nlink \u003e= max_links)\n+\tde = vfs_mkdir_no_perm(idmap, dir, dentry, mode, delegated_inode);\n+\tif (IS_ERR(de)) {\n+\t\terror = PTR_ERR(de);\n \t\tgoto err;\n-\n-\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode);\n-\tif (error)\n-\t\tgoto err;\n-\n-\tde = dir-\u003ei_op-\u003emkdir(idmap, dir, dentry, mode);\n-\terror = PTR_ERR(de);\n-\tif (IS_ERR(de))\n-\t\tgoto err;\n-\tif (de) {\n-\t\tdput(dentry);\n-\t\tdentry = de;\n \t}\n-\tfsnotify_mkdir(dir, dentry);\n-\treturn dentry;\n+\treturn de;\n \n err:\n \tend_creating(dentry);\n@@ -5703,7 +5800,7 @@ int filename_unlinkat(int dfd, struct filename name)\n \t\tgoto exit_drop_write;\n \n \t/ Why not before? Because we want correct error value /\n-\tif (unlikely(last.name[last.len])) {\n+\tif (unlikely(trailing_slashes(\u0026last))) {\n \t\tif (d_is_dir(dentry))\n \t\t\terror = -EISDIR;\n \t\telse\n@@ -6305,16 +6402,16 @@ int filename_renameat2(int olddfd, struct filename from,\n \tif (flags \u0026 RENAME_EXCHANGE) {\n \t\tif (!d_is_dir(rd.new_dentry)) {\n \t\t\terror = -ENOTDIR;\n-\t\t\tif (new_last.name[new_last.len])\n+\t\t\tif (trailing_slashes(\u0026new_last))\n \t\t\t\tgoto exit_unlock;\n \t\t}\n \t}\n \t/* unless the source is a directory trailing slashes give -ENOTDIR /\n \tif (!d_is_dir(rd.old_dentry)) {\n \t\terror = -ENOTDIR;\n-\t\tif (old_last.name[old_last.len])\n+\t\tif (trailing_slashes(\u0026old_last))\n \t\t\tgoto exit_unlock;\n-\t\tif (!(flags \u0026 RENAME_EXCHANGE) \u0026\u0026 new_last.name[new_last.len])\n+\t\tif (!(flags \u0026 RENAME_EXCHANGE) \u0026\u0026 trailing_slashes(\u0026new_last))\n \t\t\tgoto exit_unlock;\n \t}\n \ndiff --git a/fs/nfs/dir.c b/fs/nfs/dir.c\nindex 49394123bd096..4b1404d6859e8 100644\n--- a/fs/nfs/dir.c\n+++ b/fs/nfs/dir.c\n@@ -2121,6 +2121,11 @@ int nfs_atomic_open(struct inode dir, struct dentry dentry,\n \tdfprintk(VFS, \"NFS: atomic_open(%s/%llu), %pd\\n\",\n \t\t\tdir-\u003ei_sb-\u003es_id, dir-\u003ei_ino, dentry);\n \n+\tif (O_IS_MKDIR(open_flags)) {\n+\t\topen_flags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \terr = nfs_check_flags(open_flags);\n \tif (err)\n \t\treturn err;\n@@ -2317,6 +2322,11 @@ int nfs_atomic_open_v23(struct inode dir, struct dentry dentry,\n \t /\n \tint error = 0;\n \n+\tif (O_IS_MKDIR(open_flags)) {\n+\t\topen_flags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \tif (dentry-\u003ed_name.len \u003e NFS_SERVER(dir)-\u003enamelen)\n \t\treturn -ENAMETOOLONG;\n \ndiff --git a/fs/open.c b/fs/open.c\nindex 6b1c14e684a93..6cb5e2ad781f3 100644\n--- a/fs/open.c\n+++ b/fs/open.c\n@@ -1239,29 +1239,30 @@ inline int build_open_flags(const struct open_how how, struct open_flags op)\n \tif (WILL_CREATE(flags)) {\n \t\tif (how-\u003emode \u0026 ~S_IALLUGO)\n \t\t\treturn -EINVAL;\n-\t\top-\u003emode = how-\u003emode \| S_IFREG;\n+\t\tif (O_IS_MKDIR(flags))\n+\t\t\top-\u003emode = how-\u003emode \| S_IFDIR;\n+\t\telse\n+\t\t\top-\u003emode = how-\u003emode \| S_IFREG;\n \t} else {\n \t\tif (how-\u003emode != 0)\n \t\t\treturn -EINVAL;\n \t\top-\u003emode = 0;\n \t}\n \n-\t/\n-\t Block bugs where O_DIRECTORY \| O_CREAT created regular files.\n-\t * Note, that blocking O_DIRECTORY \| O_CREAT here also protects\n-\t * O_TMPFILE below which requires O_DIRECTORY being raised.\n-\t /\n-\tif ((flags \u0026 (O_DIRECTORY \| O_CREAT)) == (O_DIRECTORY \| O_CREAT))\n-\t\treturn -EINVAL;\n-\n \t/ Now handle the creative implementation of O_TMPFILE. /\n \tif (flags \u0026 __O_TMPFILE) {\n \t\t/\n \t\t * In order to ensure programs get explicit errors when trying\n \t\t * to use O_TMPFILE on old kernels we enforce that O_DIRECTORY\n-\t\t * is raised alongside __O_TMPFILE.\n+\t\t * is raised alongside __O_TMPFILE, but without O_CREAT. The\n+\t\t * reason for disallowing O_CREAT\|O_TMPFILE is that\n+\t\t * O_DIRECTORY\|O_CREAT used to work and created a regular file\n+\t\t * if nothing existed at the open path. Hence, allowing the\n+\t\t * combination would have caused O_CREAT\|O_TMPFILE to create a\n+\t\t * regular (non-temporary) file on old kernels, while the caller\n+\t\t * would believe they created an actual O_TMPFILE.\n \t\t /\n-\t\tif (!(flags \u0026 O_DIRECTORY))\n+\t\tif (!(flags \u0026 O_DIRECTORY) \|\| (flags \u0026 O_CREAT))\n \t\t\treturn -EINVAL;\n \t\tif (!(acc_mode \u0026 MAY_WRITE))\n \t\t\treturn -EINVAL;\n@@ -1318,6 +1319,15 @@ inline int build_open_flags(const struct open_how how, struct open_flags op)\n \n \top-\u003eintent = flags \u0026 O_PATH ? 0 : LOOKUP_OPEN;\n \n+\t/\n+\t * Requesting write access on a directory can never succeed. Rather\n+\t * than performing a path-walk to determine whether the target is\n+\t * actually a directory (-EISDIR) or not (-ENOTDIR), we short-circuit\n+\t * to -ENOTDIR.\n+\t /\n+\tif ((flags \u0026 O_DIRECTORY) \u0026\u0026 !(flags \u0026 __O_TMPFILE) \u0026\u0026 (acc_mode \u0026 MAY_WRITE))\n+\t\treturn -ENOTDIR;\n+\n \tif (flags \u0026 O_CREAT) {\n \t\top-\u003eintent \|= LOOKUP_CREATE;\n \t\tif (flags \u0026 O_EXCL) {\ndiff --git a/fs/smb/client/dir.c b/fs/smb/client/dir.c\nindex 6fa6d48fdfd30..f75095a48fdb1 100644\n--- a/fs/smb/client/dir.c\n+++ b/fs/smb/client/dir.c\n@@ -534,6 +534,11 @@ int cifs_atomic_open(struct inode dir, struct dentry direntry,\n \tif (unlikely(cifs_forced_shutdown(cifs_sb)))\n \t\treturn smb_EIO(smb_eio_trace_forced_shutdown);\n \n+\tif (O_IS_MKDIR(oflags)) {\n+\t\toflags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \t/\n \t * Posix open is only called (at lookup time) for file create now. For\n \t * opens (rather than creates), because we do not know if it is a file\ndiff --git a/fs/vboxsf/dir.c b/fs/vboxsf/dir.c\nindex 0b9eab157432d..f20b61f6d8da7 100644\n--- a/fs/vboxsf/dir.c\n+++ b/fs/vboxsf/dir.c\n@@ -318,6 +318,11 @@ static int vboxsf_dir_atomic_open(struct inode parent, struct dentry dentry,\n \tu64 handle;\n \tint err;\n \n+\tif (O_IS_MKDIR(flags)) {\n+\t\tflags \u0026= ~O_CREAT;\n+\t\tmode = 0;\n+\t}\n+\n \tif (d_in_lookup(dentry)) {\n \t\tstruct dentry res = vboxsf_dir_lookup(parent, dentry, 0);\n \t\tif (res \|\| d_really_is_positive(dentry))\ndiff --git a/include/linux/fcntl.h b/include/linux/fcntl.h\nindex 6ad6b9e7a226a..204e16bbe2634 100644\n--- a/include/linux/fcntl.h\n+++ b/include/linux/fcntl.h\n@@ -30,6 +30,12 @@\n /\n #define __O_REGULAR\t\t(1 \u003c\u003c 30)\n \n+#define O_MKDIR_MASK\t(O_CREAT \| O_DIRECTORY)\n+static inline bool O_IS_MKDIR(unsigned int flags)\n+{\n+\treturn (flags \u0026 O_MKDIR_MASK) == O_MKDIR_MASK;\n+}\n+\n /* List of all valid flags for the how-\u003eresolve argument: /\n #define VALID_RESOLVE_FLAGS \\\n \t(RESOLVE_NO_XDEV \| RESOLVE_NO_MAGICLINKS \| RESOLVE_NO_SYMLINKS \| \\\ndiff --git a/include/uapi/asm-generic/errno.h b/include/uapi/asm-generic/errno.h\nindex bd78e69e0a43f..c84ebf89c8b6e 100644\n--- a/include/uapi/asm-generic/errno.h\n+++ b/include/uapi/asm-generic/errno.h\n@@ -76,7 +76,7 @@\n #define\tENOPROTOOPT\t92\t/ Protocol not available /\n #define\tEPROTONOSUPPORT\t93\t/ Protocol not supported /\n #define\tESOCKTNOSUPPORT\t94\t/ Socket type not supported /\n-#define\tEOPNOTSUPP\t95\t/ Operation not supported on transport endpoint /\n+#define\tEOPNOTSUPP\t95\t/ Operation not supported /\n #define\tEPFNOSUPPORT\t96\t/ Protocol family not supported /\n #define\tEAFNOSUPPORT\t97\t/ Address family not supported by protocol /\n #define\tEADDRINUSE\t98\t/ Address already in use /\ndiff --git a/tools/testing/selftests/filesystems/.gitignore b/tools/testing/selftests/filesystems/.gitignore\nindex 9eb185fb2f9dd..01c588d4c84f6 100644\n--- a/tools/testing/selftests/filesystems/.gitignore\n+++ b/tools/testing/selftests/filesystems/.gitignore\n@@ -1,4 +1,5 @@\n # SPDX-License-Identifier: GPL-2.0-only\n+open_o_creat_o_dir\n dnotify_test\n devpts_pts\n fclog\ndiff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/selftests/filesystems/Makefile\nindex 03be337c1f351..0959bd26875ac 100644\n--- a/tools/testing/selftests/filesystems/Makefile\n+++ b/tools/testing/selftests/filesystems/Makefile\n@@ -1,7 +1,7 @@\n # SPDX-License-Identifier: GPL-2.0\n \n CFLAGS += $(KHDR_INCLUDES)\n-TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test\n+TEST_GEN_PROGS := open_o_creat_o_dir devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test\n TEST_GEN_PROGS += idmapped_tmpfile\n TEST_GEN_PROGS_EXTENDED := dnotify_test\n \ndiff --git a/tools/testing/selftests/filesystems/open_o_creat_o_dir.c b/tools/testing/selftests/filesystems/open_o_creat_o_dir.c\nnew file mode 100644\nindex 0000000000000..538a7f7c58037\n--- /dev/null\n+++ b/tools/testing/selftests/filesystems/open_o_creat_o_dir.c\n@@ -0,0 +1,296 @@\n+// SPDX-License-Identifier: GPL-2.0\n+#include \u003csys/stat.h\u003e\n+#include \u003cerrno.h\u003e\n+#include \u003climits.h\u003e\n+#include \u003cfcntl.h\u003e\n+\n+#include \"kselftest_harness.h\"\n+#include \"wrappers.h\"\n+\n+#define openat_o_mkdir_checked_flags(dfd, pathname, flags) ({\t\\\n+\tstruct stat __st;\t\t\t\t\t\t\\\n+\tint __fd = openat_o_mkdir(dfd, pathname, flags, S_IRWXU);\t\\\n+\tASSERT_GE(__fd, 0);\t\t\t\t\t\t\\\n+\tASSERT_EQ(fstat(__fd, \u0026__st), 0);\t\t\t\t\\\n+\tEXPECT_TRUE(S_ISDIR(__st.st_mode));\t\t\t\t\\\n+\t__fd;\t\t\t\t\t\t\t\t\\\n+})\n+\n+#define openat_o_mkdir_checked(dfd, pathname) \\\n+\topenat_o_mkdir_checked_flags(dfd, pathname, O_RDONLY)\n+\n+FIXTURE(open_o_creat_o_dir) {\n+\tchar dirpath[PATH_MAX];\n+\tint dfd;\n+};\n+\n+FIXTURE_SETUP(open_o_creat_o_dir)\n+{\n+\tstrcpy(self-\u003edirpath, \"/tmp/open_o_creat_o_dir_test.XXXXXX\");\n+\tASSERT_NE(mkdtemp(self-\u003edirpath), NULL);\n+\tself-\u003edfd = open(self-\u003edirpath, O_DIRECTORY);\n+\tASSERT_GE(self-\u003edfd, 0);\n+}\n+\n+FIXTURE_TEARDOWN(open_o_creat_o_dir)\n+{\n+\tclose(self-\u003edfd);\n+\trmdir(self-\u003edirpath);\n+}\n+\n+/ Does open_o_creat_o_dir return a fd at all? /\n+TEST_F(open_o_creat_o_dir, returns_fd)\n+{\n+\tint fd = openat_o_mkdir_checked(self-\u003edfd, \"newdir\");\n+\tEXPECT_EQ(close(fd), 0);\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"newdir\", AT_REMOVEDIR), 0);\n+}\n+\n+/ The fd must refer to the directory that was just created. /\n+TEST_F(open_o_creat_o_dir, fd_is_created_dir)\n+{\n+\tint fd;\n+\tstruct stat st_via_fd, st_via_path;\n+\tchar path[PATH_MAX];\n+\n+\tfd = openat_o_mkdir_checked(self-\u003edfd, \"checkdir\");\n+\n+\tASSERT_EQ(fstat(fd, \u0026st_via_fd), 0);\n+\n+\tsnprintf(path, sizeof(path), \"%s/checkdir\", self-\u003edirpath);\n+\tASSERT_EQ(stat(path, \u0026st_via_path), 0);\n+\n+\tEXPECT_EQ(st_via_fd.st_ino, st_via_path.st_ino);\n+\tEXPECT_EQ(st_via_fd.st_dev, st_via_path.st_dev);\n+\n+\tEXPECT_EQ(close(fd), 0);\n+\tEXPECT_EQ(rmdir(path), 0);\n+}\n+\n+/ Missing parent component must fail with ENOENT. /\n+TEST_F(open_o_creat_o_dir, enoent_missing_parent)\n+{\n+\tEXPECT_EQ(openat_o_mkdir(self-\u003edfd, \"nonexistent/child\", O_RDONLY, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, ENOENT);\n+}\n+\n+/ An invalid dfd must fail with EBADF. /\n+TEST_F(open_o_creat_o_dir, ebadf)\n+{\n+\tEXPECT_EQ(openat_o_mkdir(FD_INVALID, \"badfdir\", O_RDONLY, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, EBADF);\n+}\n+\n+/ A dfd that points to a file (not a directory) must fail with ENOTDIR. /\n+TEST_F(open_o_creat_o_dir, enotdir_dfd)\n+{\n+\tint file_fd;\n+\n+\tfile_fd = openat(self-\u003edfd, \"file\",\n+\t\t\t O_CREAT \| O_RDONLY, S_IRWXU);\n+\tASSERT_GE(file_fd, 0);\n+\n+\tEXPECT_EQ(openat_o_mkdir(file_fd, \"subdir\", O_RDONLY, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, ENOTDIR);\n+\n+\tEXPECT_EQ(close(file_fd), 0);\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"file\", 0), 0);\n+}\n+\n+/\n+ * O_EXCL together with O_CREAT\|O_DIRECTORY should succeed if the target\n+ * directory does not yet exist. After directory creation, repeating this\n+ * call must fail with EEXIST, but should succeed if the O_EXCL is dropped.\n+ /\n+TEST_F(open_o_creat_o_dir, o_excl_eexist)\n+{\n+\tint excldir_fd;\n+\n+\texcldir_fd = openat_o_mkdir_checked_flags(self-\u003edfd, \"excldir\", O_EXCL);\n+\n+\tEXPECT_EQ(openat_o_mkdir(self-\u003edfd, \"excldir\", O_EXCL, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, EEXIST);\n+\n+\tint excldir_reopen_fd = openat_o_mkdir_checked(self-\u003edfd, \"excldir\");\n+\n+\tEXPECT_EQ(close(excldir_reopen_fd), 0);\n+\tEXPECT_EQ(close(excldir_fd), 0);\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"excldir\", AT_REMOVEDIR), 0);\n+}\n+\n+/\n+ * O_CREAT\|O_DIRECTORY on a path that already exists as a regular file\n+ * must fail with ENOTDIR.\n+ /\n+TEST_F(open_o_creat_o_dir, existing_file_enotdir)\n+{\n+\tint file_fd;\n+\n+\tfile_fd = openat(self-\u003edfd, \"regfile\",\n+\t\t\t O_CREAT \| O_RDONLY, S_IRWXU);\n+\tASSERT_GE(file_fd, 0);\n+\tEXPECT_EQ(close(file_fd), 0);\n+\n+\tEXPECT_EQ(openat_o_mkdir(self-\u003edfd, \"regfile\", O_RDONLY, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, ENOTDIR);\n+\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"regfile\", 0), 0);\n+}\n+\n+/\n+ * O_CREAT\|O_DIRECTORY combined with a writable access mode must be\n+ * rejected: a directory cannot be opened for writing.\n+ /\n+TEST_F(open_o_creat_o_dir, rejects_writable_acc_mode)\n+{\n+\tEXPECT_EQ(openat_o_mkdir(self-\u003edfd, \"rdwrdir\", O_RDWR, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, ENOTDIR);\n+\t/ Clean up if the kernel created the directory anyway. /\n+\tunlinkat(self-\u003edfd, \"rdwrdir\", AT_REMOVEDIR);\n+}\n+\n+/\n+ * openat(O_CREAT\|O_DIRECTORY) with a trailing slash should work.\n+ /\n+TEST_F(open_o_creat_o_dir, trailing_slash)\n+{\n+\tint fd = openat_o_mkdir_checked(self-\u003edfd, \"newdir/\");\n+\tEXPECT_EQ(close(fd), 0);\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"newdir\", AT_REMOVEDIR), 0);\n+}\n+\n+/\n+ * openat(O_CREAT) with a trailing slash but without O_DIRECTORY\n+ * must fail with EISDIR and must not create anything at the path.\n+ /\n+TEST_F(open_o_creat_o_dir, trailing_slash_no_o_dir)\n+{\n+\tint fd;\n+\tstruct stat st;\n+\n+\tfd = openat(self-\u003edfd, \"trailing/\", O_CREAT \| O_RDONLY, S_IRWXU);\n+\tEXPECT_EQ(fd, -1);\n+\tEXPECT_EQ(errno, EISDIR);\n+\n+\tEXPECT_EQ(fstatat(self-\u003edfd, \"trailing\", \u0026st, 0), -1);\n+\tEXPECT_EQ(errno, ENOENT);\n+\n+\t/ Best-effort cleanup in case the kernel left a file behind. /\n+\tif (fd \u003e= 0)\n+\t\tclose(fd);\n+\tunlinkat(self-\u003edfd, \"trailing\", 0);\n+}\n+\n+/\n+ * The returned fd must be usable as a dfd for further at() calls.\n+ /\n+TEST_F(open_o_creat_o_dir, fd_usable_as_dfd)\n+{\n+\tint parent_fd, child_fd;\n+\tchar path[PATH_MAX];\n+\n+\tparent_fd = openat_o_mkdir_checked(self-\u003edfd, \"parent\");\n+\tchild_fd = openat_o_mkdir_checked(parent_fd, \"child\");\n+\n+\tEXPECT_EQ(close(child_fd), 0);\n+\tEXPECT_EQ(close(parent_fd), 0);\n+\n+\tsnprintf(path, sizeof(path), \"%s/parent/child\", self-\u003edirpath);\n+\tEXPECT_EQ(rmdir(path), 0);\n+\tsnprintf(path, sizeof(path), \"%s/parent\", self-\u003edirpath);\n+\tEXPECT_EQ(rmdir(path), 0);\n+}\n+\n+/\n+ O_CREAT\|O_DIRECTORY must refuse to create through a dangling trailing\n+ * symlink, and must not create anything at the symlink target.\n+ /\n+TEST_F(open_o_creat_o_dir, dangling_symlink_eexist)\n+{\n+\tstruct stat st;\n+\n+\tASSERT_EQ(symlinkat(\"danglink_target\", self-\u003edfd, \"danglink\"), 0);\n+\n+\tEXPECT_EQ(openat_o_mkdir(self-\u003edfd, \"danglink\", O_RDONLY, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, EEXIST);\n+\n+\t/ Nothing must have been created at the target. /\n+\tEXPECT_EQ(fstatat(self-\u003edfd, \"danglink_target\", \u0026st, 0), -1);\n+\tEXPECT_EQ(errno, ENOENT);\n+\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"danglink\", 0), 0);\n+}\n+\n+/\n+ * A trailing symlink that resolves to an existing directory must still open.\n+ /\n+TEST_F(open_o_creat_o_dir, symlink_not_dangling_ok)\n+{\n+\tint fd;\n+\n+\tASSERT_EQ(mkdirat(self-\u003edfd, \"realdir\", 0700), 0);\n+\tASSERT_EQ(symlinkat(\"realdir\", self-\u003edfd, \"dirlink\"), 0);\n+\n+\t/ Trailing symlink resolving to an existing directory. /\n+\tfd = openat_o_mkdir_checked(self-\u003edfd, \"dirlink\");\n+\tEXPECT_EQ(close(fd), 0);\n+\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"dirlink\", 0), 0);\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"realdir\", AT_REMOVEDIR), 0);\n+}\n+\n+/\n+ * An O_CREAT\|O_DIRECTORY open of an existing directory owned by someone else,\n+ * inside a sticky world-writable directory, must be refused.\n+ /\n+TEST_F(open_o_creat_o_dir, sticky_dir_eacces)\n+{\n+\tint sticky_fd, fd;\n+\n+\tif (geteuid() != 0)\n+\t\tSKIP(return, \"needs root for fchownat\");\n+\n+\tASSERT_EQ(mkdirat(self-\u003edfd, \"sticky\", 01777), 0);\n+\tASSERT_EQ(fchmodat(self-\u003edfd, \"sticky\", 01777, 0), 0);\n+\tsticky_fd = openat(self-\u003edfd, \"sticky\", O_DIRECTORY \| O_RDONLY);\n+\tASSERT_GE(sticky_fd, 0);\n+\n+\tASSERT_EQ(mkdirat(sticky_fd, \"otherdir\", 0700), 0);\n+\tif (fchownat(sticky_fd, \"otherdir\", 1, 1, 0)) {\n+\t\tint err = errno;\n+\n+\t\tunlinkat(sticky_fd, \"otherdir\", AT_REMOVEDIR);\n+\t\tclose(sticky_fd);\n+\t\tunlinkat(self-\u003edfd, \"sticky\", AT_REMOVEDIR);\n+\t\tSKIP(return, \"cannot chown to uid 1: %s\", strerror(err));\n+\t}\n+\n+\tEXPECT_EQ(openat_o_mkdir(sticky_fd, \"otherdir\", O_RDONLY, S_IRWXU), -1);\n+\tEXPECT_EQ(errno, EACCES);\n+\n+\t/ Without O_CREAT the very same open must still succeed. /\n+\tfd = openat(sticky_fd, \"otherdir\", O_DIRECTORY \| O_RDONLY);\n+\tEXPECT_GE(fd, 0);\n+\tif (fd \u003e= 0) {\n+\t\tEXPECT_EQ(close(fd), 0);\n+\t}\n+\n+\tEXPECT_EQ(unlinkat(sticky_fd, \"otherdir\", AT_REMOVEDIR), 0);\n+\tEXPECT_EQ(close(sticky_fd), 0);\n+\tEXPECT_EQ(unlinkat(self-\u003edfd, \"sticky\", AT_REMOVEDIR), 0);\n+}\n+\n+/\n+ * O_TMPFILE is encoded as __O_TMPFILE\|O_DIRECTORY. Now that O_CREAT is no\n+ * longer rejected alongside O_DIRECTORY, O_TMPFILE\|O_CREAT must still be\n+ * rejected explicitly so that it cannot create a persistent file on kernels\n+ * that predate O_TMPFILE.\n+ /\n+TEST_F(open_o_creat_o_dir, tmpfile_with_o_creat_einval)\n+{\n+\tEXPECT_EQ(openat(self-\u003edfd, \".\", O_TMPFILE \| O_CREAT \| O_RDWR, S_IRWXU),\n+\t\t -1);\n+\tEXPECT_EQ(errno, EINVAL);\n+}\n+\n+TEST_HARNESS_MAIN\ndiff --git a/tools/testing/selftests/filesystems/wrappers.h b/tools/testing/selftests/filesystems/wrappers.h\nindex 420ae4f908cf2..abe5b85cebdcd 100644\n--- a/tools/testing/selftests/filesystems/wrappers.h\n+++ b/tools/testing/selftests/filesystems/wrappers.h\n@@ -13,6 +13,10 @@\n #define STATX_MNT_ID_UNIQUE 0x00004000U / Want/got extended stx_mount_id /\n #endif\n \n+#ifndef FD_INVALID\n+#define FD_INVALID -10009\n+#endif\n+\n static inline int sys_fsopen(const char fsname, unsigned int flags)\n {\n \treturn syscall(__NR_fsopen, fsname, flags);\n@@ -105,4 +109,11 @@ static inline int sys_open_tree(int dfd, const char filename, unsigned int flag\n \treturn syscall(__NR_open_tree, dfd, filename, flags);\n }\n \n+static inline int openat_o_mkdir(int dfd, const char pathname,\n+\t\t\t\t unsigned int flags, mode_t mode)\n+{\n+\treturn syscall(__NR_openat, dfd, pathname,\n+\t\t flags \| O_DIRECTORY \| O_CREAT, mode);\n+}\n+\n #endif\n" }
2/1	2026/09/13 19:51	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "FUSE_FS", "NET_9P", "9P_FS" ], "FocusSymbols": [ "lookup_open", "may_o_create", "atomic_open", "may_create_in_sticky", "vfs_mkdir", "vfs_create", "fuse_atomic_open" ], "Reasoning": "The patch introduces support for creating directories via openat() using O_CREAT \| O_DIRECTORY, refactoring core VFS path lookup, permission checks, directory creation helpers, and inode locking, as well as updating atomic_open implementations across multiple filesystems (including FUSE and 9p). These are substantial logic changes in core VFS and reachable syscall handlers, including new runtime assertions (WARN_ON_ONCE in may_o_create) and security checks, which warrant fuzzing.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 3460f086b4bc3a2056c482324556c2230583a0f9 Author: syz-cluster <triage@syzkaller.com> Date: Sun Sep 13 19:51:27 2026 +0000 syz-cluster: applied patch under review diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c index 3829554ca3692..dd810904ff6c0 100644 --- a/fs/9p/vfs_inode.c +++ b/fs/9p/vfs_inode.c @@ -776,6 +776,11 @@ v9fs_vfs_atomic_open(struct inode dir, struct dentry dentry, struct inode inode; int p9_omode; + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (d_in_lookup(dentry)) { struct dentry res = v9fs_vfs_lookup(dir, dentry, 0); if (res \|\| d_really_is_positive(dentry)) diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 116b29e95f21e..9308184aee611 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -238,6 +238,11 @@ v9fs_vfs_atomic_open_dotl(struct inode dir, struct dentry dentry, struct v9fs_session_info v9ses; struct posix_acl pacl = NULL, dacl = NULL; + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + omode = 0; + } + if (d_in_lookup(dentry)) { struct dentry res = v9fs_vfs_lookup(dir, dentry, 0); if (res \|\| d_really_is_positive(dentry)) diff --git a/fs/ceph/file.c b/fs/ceph/file.c index bd3e3f5c269e8..9235143edd9a8 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -812,6 +812,11 @@ int ceph_atomic_open(struct inode dir, struct dentry dentry, dir, ceph_vinop(dir), dentry, dentry, d_unhashed(dentry) ? "unhashed" : "hashed", flags, mode); + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (dentry->d_name.len > NAME_MAX) return -ENAMETOOLONG; diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index e49b4e874b15f..a3e7daba61dcb 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -944,6 +944,11 @@ static int fuse_atomic_open(struct inode dir, struct dentry entry, struct mnt_idmap idmap = file_mnt_idmap(file); struct fuse_conn fc = get_fuse_conn(dir); + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (fuse_is_bad(dir)) return -EIO; diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c index f361876c55833..69e100a68e2c0 100644 --- a/fs/gfs2/inode.c +++ b/fs/gfs2/inode.c @@ -1386,6 +1386,11 @@ static int gfs2_atomic_open(struct inode dir, struct dentry dentry, { bool excl = !!(flags & O_EXCL); + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (d_in_lookup(dentry)) { struct dentry d = __gfs2_lookup(dir, dentry, file); if (file->f_mode & FMODE_OPENED) { diff --git a/fs/namei.c b/fs/namei.c index 20a6534ea3eff..fce3aaa373658 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1382,13 +1382,13 @@ int may_linkat(struct mnt_idmap idmap, const struct path link) /* * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory - * should be allowed, or not, on files that already - * exist. + * should be allowed, or not, on files/directories that + * already exist. * @idmap: idmap of the mount the inode was found from * @nd: nameidata pathwalk data * @inode: the inode of the file to open * - * Block an O_CREAT open of a FIFO (or a regular file) when: + * Block an O_CREAT open of a FIFO (or a regular file/directory) when: * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled * - the file already exists * - we are in a sticky directory @@ -1416,6 +1416,14 @@ static int may_create_in_sticky(struct mnt_idmap idmap, struct nameidata nd, if (likely(!(dir_mode & S_ISVTX))) return 0; + /* + * There is no separate sysctl for directory creation in sticky + * folders. Therefore, for the S_ISDIR case, disabling + * sysctl_protected_regular is not enough to allow creating a + * directory in a sticky folder, because that may surprise users + * not expecting that O_CREAT\|O_DIRECTORY is possible on newer + * kernels. + / if (S_ISREG(inode->i_mode) && !sysctl_protected_regular) return 0; @@ -1447,6 +1455,12 @@ static int may_create_in_sticky(struct mnt_idmap idmap, struct nameidata nd, "sticky_create_regular"); return -EACCES; } + + if (S_ISDIR(inode->i_mode)) { + audit_log_path_denied(AUDIT_ANOM_CREAT, + "sticky_create_dir"); + return -EACCES; + } } return 0; @@ -2781,9 +2795,16 @@ static const char path_init(struct nameidata nd, unsigned flags) return s; } +static inline bool trailing_slashes(const struct qstr last) +{ + /* last->len is set by hash_name() to the length of the current + * component ->name, terminating with '/' or a NUL character. / + return (bool)last->name[last->len]; +} + static inline const char lookup_last(struct nameidata nd) { - if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) + if (nd->last_type == LAST_NORM && trailing_slashes(&nd->last)) nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY; return walk_component(nd, WALK_TRAILING); @@ -4159,6 +4180,24 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap idmap, return mode; } +static inline +int vfs_create_no_perm(struct mnt_idmap idmap, struct dentry dentry, + umode_t mode, struct delegated_inode di) +{ + struct inode dir = d_inode(dentry->d_parent); + int error; + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); + if (error) + return error; + + error = dir->i_op->create(idmap, dir, dentry, mode); + if (!error) + fsnotify_create(dir, dentry); + + return error; +} + /** * vfs_create - create new file * @idmap: idmap of the mount the inode was found from @@ -4185,19 +4224,14 @@ int vfs_create(struct mnt_idmap idmap, struct dentry dentry, umode_t mode, return error; if (!dir->i_op->create) - return -EACCES; /* shouldn't it be ENOSYS? / + return -EOPNOTSUPP; mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG); error = security_inode_create(dir, dentry, mode); if (error) return error; - error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); - if (error) - return error; - error = dir->i_op->create(idmap, dir, dentry, mode); - if (!error) - fsnotify_create(dir, dentry); - return error; + + return vfs_create_no_perm(idmap, dentry, mode, di); } EXPORT_SYMBOL(vfs_create); @@ -4314,21 +4348,43 @@ static inline int open_to_namei_flags(int flag) static int may_o_create(struct mnt_idmap idmap, const struct path dir, struct dentry dentry, - umode_t mode) + int open_flag, umode_t mode) { - int error = security_path_mknod(dir, dentry, mode, 0); + struct inode dir_inode = dir->dentry->d_inode; + bool create_dir = O_IS_MKDIR(open_flag); + int error; + + WARN_ON_ONCE(create_dir && !(mode & S_IFDIR)); + + if (create_dir) + error = security_path_mkdir(dir, dentry, mode); + else + error = security_path_mknod(dir, dentry, mode, 0); if (error) return error; if (!fsuidgid_has_mapping(dir->dentry->d_sb, idmap)) return -EOVERFLOW; - error = inode_permission(idmap, dir->dentry->d_inode, - MAY_WRITE \| MAY_EXEC); + error = inode_permission(idmap, dir_inode, MAY_WRITE \| MAY_EXEC); if (error) return error; - return security_inode_create(dir->dentry->d_inode, dentry, mode); + if (create_dir) + error = security_inode_mkdir(dir_inode, dentry, mode); + else + error = security_inode_create(dir_inode, dentry, mode); + + return error; +} + +static inline umode_t o_create_mode(struct mnt_idmap idmap, + const struct inode dir, int open_flag, umode_t mode) +{ + if (O_IS_MKDIR(open_flag)) + return vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO \| S_ISVTX, S_IFDIR); + else + return vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG); } /* @@ -4364,8 +4420,9 @@ static struct dentry atomic_open(const struct path path, struct dentry dentry file->__f_path.dentry = DENTRY_NOT_SET; file->__f_path.mnt = path->mnt; + error = dir_inode->i_op->atomic_open(dir_inode, dentry, file, - open_to_namei_flags(open_flag), mode); + open_to_namei_flags(open_flag), mode); d_lookup_done(dentry); if (!error) { @@ -4407,13 +4464,43 @@ static struct dentry atomic_open(const struct path path, struct dentry dentry / audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); error = create_error; + } else if (O_IS_MKDIR(open_flag) && error == -ENOENT) { + / + * If the underlying filesystem does not implement + * O_CREAT\|O_DIRECTORY, it strips the O_CREAT bit and + * continues as a lookup. We can't simply return + * -EOPNOTSUPP from unsupported ->atomic_open() + * implementations because the dentry might be in the + * dcache. In that case, lookup_open() returns before + * reaching ->atomic_open(), and hence whether you get + * -EOPNOTSUPP on O_CREAT\|O_DIRECTORY would not only + * depend on the underlying filesystem, but also on + * the state of the dcache. Still, we must make an + * effort to differentiate a regular -ENOENT from the + * unsupported O_CREAT\|O_DIRECTORY case. + / + error = -EOPNOTSUPP; } dput(dentry); dentry = ERR_PTR(error); + } else { + if (file->f_mode & FMODE_CREATED) { + if (d_is_dir(dentry)) + fsnotify_mkdir(dir_inode, dentry); + else + fsnotify_create(dir_inode, dentry); + } + if (file->f_mode & FMODE_OPENED) + fsnotify_open(file); } + + return dentry; } +static inline +struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry , + umode_t, struct delegated_inode ); /* * Look up and maybe create and open the last component. * @@ -4435,6 +4522,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, struct mnt_idmap idmap; struct dentry dir = nd->path.dentry; struct inode dir_inode = dir->d_inode; + bool create_dir = O_IS_MKDIR(op->open_flag); int open_flag; struct dentry dentry; int error, create_error; @@ -4455,7 +4543,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, / } if (open_flag & O_CREAT) - inode_lock(dir_inode); + inode_lock_nested(dir_inode, I_MUTEX_PARENT); else inode_lock_shared(dir_inode); @@ -4507,12 +4595,17 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, if (open_flag & O_CREAT) { if (open_flag & O_EXCL) open_flag &= ~O_TRUNC; - mode = vfs_prepare_mode(idmap, dir_inode, mode, mode, mode); + mode = o_create_mode(idmap, dir_inode, open_flag, mode); if (likely(got_write)) create_error = may_o_create(idmap, &nd->path, - dentry, mode); + dentry, open_flag, mode); else create_error = -EROFS; + /* Refuse to create a directory through a dangling (trailing) + * symlink. For regular files this has been allowed historically + * on O_CREAT without O_EXCL. / + if (unlikely(nd->depth) && create_dir && !create_error) + create_error = -EEXIST; } if (create_error) open_flag &= ~O_CREAT; @@ -4537,6 +4630,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, dentry = res; } } + if (dentry->d_inode \|\| !(op->open_flag & O_CREAT)) { /* * No need to create a file. If lookup returned a positive @@ -4554,26 +4648,26 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, goto out_dput; } - error = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE, &delegated_inode); - if (error) - goto out_dput; - - file->f_mode \|= FMODE_CREATED; - if (!dir_inode->i_op->create) { - error = -EACCES; + if ((create_dir && !dir_inode->i_op->mkdir) + \|\| (!create_dir && !dir_inode->i_op->create)) { + error = -EOPNOTSUPP; goto out_dput; } - error = dir_inode->i_op->create(idmap, dir_inode, dentry, mode); + if (create_dir) { + struct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode, + &delegated_inode); + error = PTR_ERR_OR_ZERO(res); + if (!error) + dentry = res; + } else { + error = vfs_create_no_perm(idmap, dentry, mode, &delegated_inode); + } if (error) goto out_dput; + + file->f_mode \|= FMODE_CREATED; out: - if (!IS_ERR(dentry)) { - if (file->f_mode & FMODE_CREATED) - fsnotify_create(dir_inode, dentry); - if (file->f_mode & FMODE_OPENED) - fsnotify_open(file); - } if ((open_flag & O_CREAT) \|\| create_error) inode_unlock(dir_inode); else @@ -4695,17 +4789,12 @@ struct file vfs_lookup_open(struct path parent, struct qstr last, } EXPORT_SYMBOL_FOR_MODULES(vfs_lookup_open, "nfsd"); -static inline bool trailing_slashes(struct nameidata nd) -{ - return (bool)nd->last.name[nd->last.len]; -} - static struct dentry lookup_fast_for_open(struct nameidata nd, int open_flag) { struct dentry dentry; if (open_flag & O_CREAT) { - if (trailing_slashes(nd)) + if (trailing_slashes(&nd->last) && !(open_flag & O_DIRECTORY)) return ERR_PTR(-EISDIR); / Don't bother on an O_EXCL create / @@ -4713,7 +4802,7 @@ static struct dentry lookup_fast_for_open(struct nameidata nd, int open_flag) return NULL; } - if (trailing_slashes(nd)) + if (trailing_slashes(&nd->last)) nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY; dentry = lookup_fast(nd); @@ -4806,8 +4895,9 @@ static int do_open(struct nameidata nd, if (open_flag & O_CREAT) { if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED)) return -EEXIST; - if (d_is_dir(nd->path.dentry)) + if (!(open_flag & O_DIRECTORY) && d_is_dir(nd->path.dentry)) return -EISDIR; + error = may_create_in_sticky(idmap, nd, d_backing_inode(nd->path.dentry)); if (unlikely(error)) @@ -5087,7 +5177,7 @@ static struct dentry filename_create(int dfd, struct filename name, * Do the final lookup. Suppress 'create' if there is a trailing * '/', and a directory wasn't requested. / - if (last.name[last.len] && !want_dir) + if (trailing_slashes(&last) && !want_dir) create_flags &= ~LOOKUP_CREATE; dentry = start_dirop(path->dentry, &last, reval_flag \| create_flags); if (IS_ERR(dentry)) @@ -5145,7 +5235,7 @@ inline struct dentry start_creating_user_path( EXPORT_SYMBOL(start_creating_user_path); /** - * dentry_create - Create and open a file + * dentry_create - Create and open a regular file * @path: path to create * @flags: O\_ flags * @mode: mode bits for new file @@ -5182,7 +5272,7 @@ struct file dentry_create(struct path path, int flags, umode_t mode, path->dentry = dir; mode = vfs_prepare_mode(idmap, dir_inode, mode, S_IALLUGO, S_IFREG); - create_error = may_o_create(idmap, path, dentry, mode); + create_error = may_o_create(idmap, path, dentry, flags, mode); if (create_error) flags &= ~O_CREAT; @@ -5198,13 +5288,6 @@ struct file dentry_create(struct path path, int flags, umode_t mode, /* Drop the extra reference / dput(orig_dentry); - if (!error) { - if (file->f_mode & FMODE_CREATED) - fsnotify_create(dir->d_inode, dentry); - if (file->f_mode & FMODE_OPENED) - fsnotify_open(file); - } - path->dentry = dentry; } else { @@ -5356,6 +5439,33 @@ SYSCALL_DEFINE3(mknod, const char __user , filename, umode_t, mode, unsigned, d return filename_mknodat(AT_FDCWD, name, mode, dev); } +static inline +struct dentry vfs_mkdir_no_perm(struct mnt_idmap idmap, struct inode dir, + struct dentry dentry, umode_t mode, + struct delegated_inode di) +{ + unsigned max_links = dir->i_sb->s_max_links; + struct dentry de; + int error; + + if (max_links && dir->i_nlink >= max_links) + return ERR_PTR(-EMLINK); + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); + if (error) + return ERR_PTR(error); + + de = dir->i_op->mkdir(idmap, dir, dentry, mode); + if (IS_ERR(de)) + return de; + if (de) { + dput(dentry); + dentry = de; + } + fsnotify_mkdir(dir, dentry); + return dentry; +} + /** * vfs_mkdir - create directory returning correct dentry if possible * @idmap: idmap of the mount the inode was found from @@ -5383,14 +5493,13 @@ struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir, struct delegated_inode delegated_inode) { int error; - unsigned max_links = dir->i_sb->s_max_links; struct dentry de; error = may_create_dentry(idmap, dir, dentry); if (error) goto err; - error = -EPERM; + error = -EOPNOTSUPP; if (!dir->i_op->mkdir) goto err; @@ -5399,24 +5508,12 @@ struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir, if (error) goto err; - error = -EMLINK; - if (max_links && dir->i_nlink >= max_links) + de = vfs_mkdir_no_perm(idmap, dir, dentry, mode, delegated_inode); + if (IS_ERR(de)) { + error = PTR_ERR(de); goto err; - - error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode); - if (error) - goto err; - - de = dir->i_op->mkdir(idmap, dir, dentry, mode); - error = PTR_ERR(de); - if (IS_ERR(de)) - goto err; - if (de) { - dput(dentry); - dentry = de; } - fsnotify_mkdir(dir, dentry); - return dentry; + return de; err: end_creating(dentry); @@ -5703,7 +5800,7 @@ int filename_unlinkat(int dfd, struct filename name) goto exit_drop_write; / Why not before? Because we want correct error value / - if (unlikely(last.name[last.len])) { + if (unlikely(trailing_slashes(&last))) { if (d_is_dir(dentry)) error = -EISDIR; else @@ -6305,16 +6402,16 @@ int filename_renameat2(int olddfd, struct filename from, if (flags & RENAME_EXCHANGE) { if (!d_is_dir(rd.new_dentry)) { error = -ENOTDIR; - if (new_last.name[new_last.len]) + if (trailing_slashes(&new_last)) goto exit_unlock; } } /* unless the source is a directory trailing slashes give -ENOTDIR / if (!d_is_dir(rd.old_dentry)) { error = -ENOTDIR; - if (old_last.name[old_last.len]) + if (trailing_slashes(&old_last)) goto exit_unlock; - if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) + if (!(flags & RENAME_EXCHANGE) && trailing_slashes(&new_last)) goto exit_unlock; } diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 49394123bd096..4b1404d6859e8 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2121,6 +2121,11 @@ int nfs_atomic_open(struct inode dir, struct dentry dentry, dfprintk(VFS, "NFS: atomic_open(%s/%llu), %pd\n", dir->i_sb->s_id, dir->i_ino, dentry); + if (O_IS_MKDIR(open_flags)) { + open_flags &= ~O_CREAT; + mode = 0; + } + err = nfs_check_flags(open_flags); if (err) return err; @@ -2317,6 +2322,11 @@ int nfs_atomic_open_v23(struct inode dir, struct dentry dentry, / int error = 0; + if (O_IS_MKDIR(open_flags)) { + open_flags &= ~O_CREAT; + mode = 0; + } + if (dentry->d_name.len > NFS_SERVER(dir)->namelen) return -ENAMETOOLONG; diff --git a/fs/open.c b/fs/open.c index 6b1c14e684a93..6cb5e2ad781f3 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1239,29 +1239,30 @@ inline int build_open_flags(const struct open_how how, struct open_flags op) if (WILL_CREATE(flags)) { if (how->mode & ~S_IALLUGO) return -EINVAL; - op->mode = how->mode \| S_IFREG; + if (O_IS_MKDIR(flags)) + op->mode = how->mode \| S_IFDIR; + else + op->mode = how->mode \| S_IFREG; } else { if (how->mode != 0) return -EINVAL; op->mode = 0; } - /* - * Block bugs where O_DIRECTORY \| O_CREAT created regular files. - * Note, that blocking O_DIRECTORY \| O_CREAT here also protects - * O_TMPFILE below which requires O_DIRECTORY being raised. - / - if ((flags & (O_DIRECTORY \| O_CREAT)) == (O_DIRECTORY \| O_CREAT)) - return -EINVAL; - / Now handle the creative implementation of O_TMPFILE. / if (flags & __O_TMPFILE) { / * In order to ensure programs get explicit errors when trying * to use O_TMPFILE on old kernels we enforce that O_DIRECTORY - * is raised alongside __O_TMPFILE. + * is raised alongside __O_TMPFILE, but without O_CREAT. The + * reason for disallowing O_CREAT\|O_TMPFILE is that + * O_DIRECTORY\|O_CREAT used to work and created a regular file + * if nothing existed at the open path. Hence, allowing the + * combination would have caused O_CREAT\|O_TMPFILE to create a + * regular (non-temporary) file on old kernels, while the caller + * would believe they created an actual O_TMPFILE. / - if (!(flags & O_DIRECTORY)) + if (!(flags & O_DIRECTORY) \|\| (flags & O_CREAT)) return -EINVAL; if (!(acc_mode & MAY_WRITE)) return -EINVAL; @@ -1318,6 +1319,15 @@ inline int build_open_flags(const struct open_how how, struct open_flags op) op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN; + / + * Requesting write access on a directory can never succeed. Rather + * than performing a path-walk to determine whether the target is + * actually a directory (-EISDIR) or not (-ENOTDIR), we short-circuit + * to -ENOTDIR. + / + if ((flags & O_DIRECTORY) && !(flags & __O_TMPFILE) && (acc_mode & MAY_WRITE)) + return -ENOTDIR; + if (flags & O_CREAT) { op->intent \|= LOOKUP_CREATE; if (flags & O_EXCL) { diff --git a/fs/smb/client/dir.c b/fs/smb/client/dir.c index 6fa6d48fdfd30..f75095a48fdb1 100644 --- a/fs/smb/client/dir.c +++ b/fs/smb/client/dir.c @@ -534,6 +534,11 @@ int cifs_atomic_open(struct inode dir, struct dentry direntry, if (unlikely(cifs_forced_shutdown(cifs_sb))) return smb_EIO(smb_eio_trace_forced_shutdown); + if (O_IS_MKDIR(oflags)) { + oflags &= ~O_CREAT; + mode = 0; + } + / * Posix open is only called (at lookup time) for file create now. For * opens (rather than creates), because we do not know if it is a file diff --git a/fs/vboxsf/dir.c b/fs/vboxsf/dir.c index 0b9eab157432d..f20b61f6d8da7 100644 --- a/fs/vboxsf/dir.c +++ b/fs/vboxsf/dir.c @@ -318,6 +318,11 @@ static int vboxsf_dir_atomic_open(struct inode parent, struct dentry dentry, u64 handle; int err; + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (d_in_lookup(dentry)) { struct dentry res = vboxsf_dir_lookup(parent, dentry, 0); if (res \|\| d_really_is_positive(dentry)) diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index 6ad6b9e7a226a..204e16bbe2634 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -30,6 +30,12 @@ / #define __O_REGULAR (1 << 30) +#define O_MKDIR_MASK (O_CREAT \| O_DIRECTORY) +static inline bool O_IS_MKDIR(unsigned int flags) +{ + return (flags & O_MKDIR_MASK) == O_MKDIR_MASK; +} + /* List of all valid flags for the how->resolve argument: / #define VALID_RESOLVE_FLAGS \ (RESOLVE_NO_XDEV \| RESOLVE_NO_MAGICLINKS \| RESOLVE_NO_SYMLINKS \| \ diff --git a/include/uapi/asm-generic/errno.h b/include/uapi/asm-generic/errno.h index bd78e69e0a43f..c84ebf89c8b6e 100644 --- a/include/uapi/asm-generic/errno.h +++ b/include/uapi/asm-generic/errno.h @@ -76,7 +76,7 @@ #define ENOPROTOOPT 92 / Protocol not available / #define EPROTONOSUPPORT 93 / Protocol not supported / #define ESOCKTNOSUPPORT 94 / Socket type not supported / -#define EOPNOTSUPP 95 / Operation not supported on transport endpoint / +#define EOPNOTSUPP 95 / Operation not supported / #define EPFNOSUPPORT 96 / Protocol family not supported / #define EAFNOSUPPORT 97 / Address family not supported by protocol / #define EADDRINUSE 98 / Address already in use / diff --git a/tools/testing/selftests/filesystems/.gitignore b/tools/testing/selftests/filesystems/.gitignore index 9eb185fb2f9dd..01c588d4c84f6 100644 --- a/tools/testing/selftests/filesystems/.gitignore +++ b/tools/testing/selftests/filesystems/.gitignore @@ -1,4 +1,5 @@ # SPDX-License-Identifier: GPL-2.0-only +open_o_creat_o_dir dnotify_test devpts_pts fclog diff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/selftests/filesystems/Makefile index 03be337c1f351..0959bd26875ac 100644 --- a/tools/testing/selftests/filesystems/Makefile +++ b/tools/testing/selftests/filesystems/Makefile @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 CFLAGS += $(KHDR_INCLUDES) -TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test +TEST_GEN_PROGS := open_o_creat_o_dir devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test TEST_GEN_PROGS += idmapped_tmpfile TEST_GEN_PROGS_EXTENDED := dnotify_test diff --git a/tools/testing/selftests/filesystems/open_o_creat_o_dir.c b/tools/testing/selftests/filesystems/open_o_creat_o_dir.c new file mode 100644 index 0000000000000..538a7f7c58037 --- /dev/null +++ b/tools/testing/selftests/filesystems/open_o_creat_o_dir.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <sys/stat.h> +#include <errno.h> +#include <limits.h> +#include <fcntl.h> + +#include "kselftest_harness.h" +#include "wrappers.h" + +#define openat_o_mkdir_checked_flags(dfd, pathname, flags) ({ \ + struct stat __st; \ + int __fd = openat_o_mkdir(dfd, pathname, flags, S_IRWXU); \ + ASSERT_GE(__fd, 0); \ + ASSERT_EQ(fstat(__fd, &__st), 0); \ + EXPECT_TRUE(S_ISDIR(__st.st_mode)); \ + __fd; \ +}) + +#define openat_o_mkdir_checked(dfd, pathname) \ + openat_o_mkdir_checked_flags(dfd, pathname, O_RDONLY) + +FIXTURE(open_o_creat_o_dir) { + char dirpath[PATH_MAX]; + int dfd; +}; + +FIXTURE_SETUP(open_o_creat_o_dir) +{ + strcpy(self->dirpath, "/tmp/open_o_creat_o_dir_test.XXXXXX"); + ASSERT_NE(mkdtemp(self->dirpath), NULL); + self->dfd = open(self->dirpath, O_DIRECTORY); + ASSERT_GE(self->dfd, 0); +} + +FIXTURE_TEARDOWN(open_o_creat_o_dir) +{ + close(self->dfd); + rmdir(self->dirpath); +} + +/ Does open_o_creat_o_dir return a fd at all? / +TEST_F(open_o_creat_o_dir, returns_fd) +{ + int fd = openat_o_mkdir_checked(self->dfd, "newdir"); + EXPECT_EQ(close(fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "newdir", AT_REMOVEDIR), 0); +} + +/ The fd must refer to the directory that was just created. / +TEST_F(open_o_creat_o_dir, fd_is_created_dir) +{ + int fd; + struct stat st_via_fd, st_via_path; + char path[PATH_MAX]; + + fd = openat_o_mkdir_checked(self->dfd, "checkdir"); + + ASSERT_EQ(fstat(fd, &st_via_fd), 0); + + snprintf(path, sizeof(path), "%s/checkdir", self->dirpath); + ASSERT_EQ(stat(path, &st_via_path), 0); + + EXPECT_EQ(st_via_fd.st_ino, st_via_path.st_ino); + EXPECT_EQ(st_via_fd.st_dev, st_via_path.st_dev); + + EXPECT_EQ(close(fd), 0); + EXPECT_EQ(rmdir(path), 0); +} + +/ Missing parent component must fail with ENOENT. / +TEST_F(open_o_creat_o_dir, enoent_missing_parent) +{ + EXPECT_EQ(openat_o_mkdir(self->dfd, "nonexistent/child", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, ENOENT); +} + +/ An invalid dfd must fail with EBADF. / +TEST_F(open_o_creat_o_dir, ebadf) +{ + EXPECT_EQ(openat_o_mkdir(FD_INVALID, "badfdir", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, EBADF); +} + +/ A dfd that points to a file (not a directory) must fail with ENOTDIR. / +TEST_F(open_o_creat_o_dir, enotdir_dfd) +{ + int file_fd; + + file_fd = openat(self->dfd, "file", + O_CREAT \| O_RDONLY, S_IRWXU); + ASSERT_GE(file_fd, 0); + + EXPECT_EQ(openat_o_mkdir(file_fd, "subdir", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, ENOTDIR); + + EXPECT_EQ(close(file_fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "file", 0), 0); +} + +/ + * O_EXCL together with O_CREAT\|O_DIRECTORY should succeed if the target + * directory does not yet exist. After directory creation, repeating this + * call must fail with EEXIST, but should succeed if the O_EXCL is dropped. + / +TEST_F(open_o_creat_o_dir, o_excl_eexist) +{ + int excldir_fd; + + excldir_fd = openat_o_mkdir_checked_flags(self->dfd, "excldir", O_EXCL); + + EXPECT_EQ(openat_o_mkdir(self->dfd, "excldir", O_EXCL, S_IRWXU), -1); + EXPECT_EQ(errno, EEXIST); + + int excldir_reopen_fd = openat_o_mkdir_checked(self->dfd, "excldir"); + + EXPECT_EQ(close(excldir_reopen_fd), 0); + EXPECT_EQ(close(excldir_fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "excldir", AT_REMOVEDIR), 0); +} + +/ + * O_CREAT\|O_DIRECTORY on a path that already exists as a regular file + * must fail with ENOTDIR. + / +TEST_F(open_o_creat_o_dir, existing_file_enotdir) +{ + int file_fd; + + file_fd = openat(self->dfd, "regfile", + O_CREAT \| O_RDONLY, S_IRWXU); + ASSERT_GE(file_fd, 0); + EXPECT_EQ(close(file_fd), 0); + + EXPECT_EQ(openat_o_mkdir(self->dfd, "regfile", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, ENOTDIR); + + EXPECT_EQ(unlinkat(self->dfd, "regfile", 0), 0); +} + +/ + * O_CREAT\|O_DIRECTORY combined with a writable access mode must be + * rejected: a directory cannot be opened for writing. + / +TEST_F(open_o_creat_o_dir, rejects_writable_acc_mode) +{ + EXPECT_EQ(openat_o_mkdir(self->dfd, "rdwrdir", O_RDWR, S_IRWXU), -1); + EXPECT_EQ(errno, ENOTDIR); + / Clean up if the kernel created the directory anyway. / + unlinkat(self->dfd, "rdwrdir", AT_REMOVEDIR); +} + +/ + * openat(O_CREAT\|O_DIRECTORY) with a trailing slash should work. + / +TEST_F(open_o_creat_o_dir, trailing_slash) +{ + int fd = openat_o_mkdir_checked(self->dfd, "newdir/"); + EXPECT_EQ(close(fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "newdir", AT_REMOVEDIR), 0); +} + +/ + * openat(O_CREAT) with a trailing slash but without O_DIRECTORY + * must fail with EISDIR and must not create anything at the path. + / +TEST_F(open_o_creat_o_dir, trailing_slash_no_o_dir) +{ + int fd; + struct stat st; + + fd = openat(self->dfd, "trailing/", O_CREAT \| O_RDONLY, S_IRWXU); + EXPECT_EQ(fd, -1); + EXPECT_EQ(errno, EISDIR); + + EXPECT_EQ(fstatat(self->dfd, "trailing", &st, 0), -1); + EXPECT_EQ(errno, ENOENT); + + / Best-effort cleanup in case the kernel left a file behind. / + if (fd >= 0) + close(fd); + unlinkat(self->dfd, "trailing", 0); +} + +/ + * The returned fd must be usable as a dfd for further at() calls. + / +TEST_F(open_o_creat_o_dir, fd_usable_as_dfd) +{ + int parent_fd, child_fd; + char path[PATH_MAX]; + + parent_fd = openat_o_mkdir_checked(self->dfd, "parent"); + child_fd = openat_o_mkdir_checked(parent_fd, "child"); + + EXPECT_EQ(close(child_fd), 0); + EXPECT_EQ(close(parent_fd), 0); + + snprintf(path, sizeof(path), "%s/parent/child", self->dirpath); + EXPECT_EQ(rmdir(path), 0); + snprintf(path, sizeof(path), "%s/parent", self->dirpath); + EXPECT_EQ(rmdir(path), 0); +} + +/* + * O_CREAT\|O_DIRECTORY must refuse to create through a dangling trailing + * symlink, and must not create anything at the symlink target. + / +TEST_F(open_o_creat_o_dir, dangling_symlink_eexist) +{ + struct stat st; + + ASSERT_EQ(symlinkat("danglink_target", self->dfd, "danglink"), 0); + + EXPECT_EQ(openat_o_mkdir(self->dfd, "danglink", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, EEXIST); + + / Nothing must have been created at the target. / + EXPECT_EQ(fstatat(self->dfd, "danglink_target", &st, 0), -1); + EXPECT_EQ(errno, ENOENT); + + EXPECT_EQ(unlinkat(self->dfd, "danglink", 0), 0); +} + +/ + * A trailing symlink that resolves to an existing directory must still open. + / +TEST_F(open_o_creat_o_dir, symlink_not_dangling_ok) +{ + int fd; + + ASSERT_EQ(mkdirat(self->dfd, "realdir", 0700), 0); + ASSERT_EQ(symlinkat("realdir", self->dfd, "dirlink"), 0); + + / Trailing symlink resolving to an existing directory. / + fd = openat_o_mkdir_checked(self->dfd, "dirlink"); + EXPECT_EQ(close(fd), 0); + + EXPECT_EQ(unlinkat(self->dfd, "dirlink", 0), 0); + EXPECT_EQ(unlinkat(self->dfd, "realdir", AT_REMOVEDIR), 0); +} + +/ + * An O_CREAT\|O_DIRECTORY open of an existing directory owned by someone else, + * inside a sticky world-writable directory, must be refused. + / +TEST_F(open_o_creat_o_dir, sticky_dir_eacces) +{ + int sticky_fd, fd; + + if (geteuid() != 0) + SKIP(return, "needs root for fchownat"); + + ASSERT_EQ(mkdirat(self->dfd, "sticky", 01777), 0); + ASSERT_EQ(fchmodat(self->dfd, "sticky", 01777, 0), 0); + sticky_fd = openat(self->dfd, "sticky", O_DIRECTORY \| O_RDONLY); + ASSERT_GE(sticky_fd, 0); + + ASSERT_EQ(mkdirat(sticky_fd, "otherdir", 0700), 0); + if (fchownat(sticky_fd, "otherdir", 1, 1, 0)) { + int err = errno; + + unlinkat(sticky_fd, "otherdir", AT_REMOVEDIR); + close(sticky_fd); + unlinkat(self->dfd, "sticky", AT_REMOVEDIR); + SKIP(return, "cannot chown to uid 1: %s", strerror(err)); + } + + EXPECT_EQ(openat_o_mkdir(sticky_fd, "otherdir", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, EACCES); + + / Without O_CREAT the very same open must still succeed. / + fd = openat(sticky_fd, "otherdir", O_DIRECTORY \| O_RDONLY); + EXPECT_GE(fd, 0); + if (fd >= 0) { + EXPECT_EQ(close(fd), 0); + } + + EXPECT_EQ(unlinkat(sticky_fd, "otherdir", AT_REMOVEDIR), 0); + EXPECT_EQ(close(sticky_fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "sticky", AT_REMOVEDIR), 0); +} + +/ + * O_TMPFILE is encoded as __O_TMPFILE\|O_DIRECTORY. Now that O_CREAT is no + * longer rejected alongside O_DIRECTORY, O_TMPFILE\|O_CREAT must still be + * rejected explicitly so that it cannot create a persistent file on kernels + * that predate O_TMPFILE. + / +TEST_F(open_o_creat_o_dir, tmpfile_with_o_creat_einval) +{ + EXPECT_EQ(openat(self->dfd, ".", O_TMPFILE \| O_CREAT \| O_RDWR, S_IRWXU), + -1); + EXPECT_EQ(errno, EINVAL); +} + +TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/filesystems/wrappers.h b/tools/testing/selftests/filesystems/wrappers.h index 420ae4f908cf2..abe5b85cebdcd 100644 --- a/tools/testing/selftests/filesystems/wrappers.h +++ b/tools/testing/selftests/filesystems/wrappers.h @@ -13,6 +13,10 @@ #define STATX_MNT_ID_UNIQUE 0x00004000U / Want/got extended stx_mount_id / #endif +#ifndef FD_INVALID +#define FD_INVALID -10009 +#endif + static inline int sys_fsopen(const char fsname, unsigned int flags) { return syscall(__NR_fsopen, fsname, flags); @@ -105,4 +109,11 @@ static inline int sys_open_tree(int dfd, const char filename, unsigned int flag return syscall(__NR_open_tree, dfd, filename, flags); } +static inline int openat_o_mkdir(int dfd, const char pathname, + unsigned int flags, mode_t mode) +{ + return syscall(__NR_openat, dfd, pathname, + flags \| O_DIRECTORY \| O_CREAT, mode); +} + #endif
3/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16922 output: 52 thoughts: 1005 Thoughts: Patch Analysis: Directory Creation with O_CREAT \| O_DIRECTORY Okay, here's the breakdown of this patch as I see it. We have a patch up for review, and it's making some significant changes to the VFS. My first pass shows that this is more than just a minor tweak; this is a fundamental alteration to how the kernel handles directory creation via `openat`. I see that the patch touches a wide range of files: `fs/9p/vfs_inode.c`, `fs/ceph/file.c`, `fs/fuse/dir.c`, and many others – spanning several filesystems, as well as core VFS components and includes. Specifically, it's modifying core VFS components related to path lookup, name resolution, permission checks, and, crucially, functions like `atomic_open` which is where the real action will take place. The change effectively allows creating directories using `openat` with the `O_CREAT \| O_DIRECTORY` flags. Previously, this combination returned `-EINVAL`. Now, it creates the directory. This is big. This impacts a large amount of core VFS code and syscall handling. I can see that it's altering functions like `atomic_open` in numerous filesystems. It's a fundamental change that's directly reachable from userspace via `open`, `openat`, and `openat2`. This change is definitely `WorthFuzzing = true`. No question about it. Looking deeper, the patch touches various functions, including: * `fs/namei.c`: * `may_create_in_sticky` (static) * `lookup_last` (static inline) * `vfs_create_no_perm` (static inline) * `vfs_create` (exported) * `may_o_create` (static) * `o_create_mode` (static inline) * `atomic_open` (static) * `lookup_open` (static) * `lookup_fast_for_open` (static) * `do_open` (static) * `filename_create` (static) * `dentry_create` (exported) * `vfs_mkdir_no_perm` (static inline) * `vfs_mkdir` (exported) * `filename_unlinkat` * `filename_renameat2` * `fs/open.c`: * `build_open_flags` (inline) * `do_sys_openat2` * Filesystem `atomic_open` implementations: * `v9fs_vfs_atomic_open` * `v9fs_vfs_atomic_open_dotl` * `ceph_atomic_open` * `fuse_atomic_open` * `gfs2_atomic_open` * `nfs_atomic_open` * `nfs_atomic_open_v23` * `cifs_atomic_open` * `vboxsf_dir_atomic_open` My next steps are to confirm the visibility of these symbols, especially the static ones, to see if they are compiled as distinct symbols. I'll need to dig into `fs/open.c` and `fs/namei.c` to see which ones are non-static and visible, to help me in focus fuzzing.
4/2	2026/09/13 19:51	tool	grepper	0m Args: { "Expression": "(lookup_open\|do_open\|atomic_open\|may_o_create\|vfs_mkdir\|build_open_flags)", "PathPrefix": "fs/" } Results: { "Output": "\nFull output is too long, showing 500 out of 784 lines.\nUse more precise expression if possible.\n\nfs/9p/vfs_inode.c=579=v9fs_create(struct v9fs_session_info v9ses, struct inode dir,\n--\nfs/9p/vfs_inode.c-648- \nfs/9p/vfs_inode.c:649: open(.., O_CREAT) is handled in v9fs_vfs_atomic_open(). This is only called\nfs/9p/vfs_inode.c-650- * for mknod(2).\n--\nfs/9p/vfs_inode.c=655=v9fs_vfs_create(struct mnt_idmap idmap, struct inode dir,\n--\nfs/9p/vfs_inode.c-673-/*\nfs/9p/vfs_inode.c:674: v9fs_vfs_mkdir - VFS mkdir hook to create a directory\nfs/9p/vfs_inode.c-675- * @idmap: idmap of the mount\n--\nfs/9p/vfs_inode.c-681-\nfs/9p/vfs_inode.c:682:static struct dentry v9fs_vfs_mkdir(struct mnt_idmap idmap, struct inode dir,\nfs/9p/vfs_inode.c-683-\t\t\t\t struct dentry dentry, umode_t mode)\n--\nfs/9p/vfs_inode.c=767=static int\nfs/9p/vfs_inode.c:768:v9fs_vfs_atomic_open(struct inode dir, struct dentry dentry,\nfs/9p/vfs_inode.c-769-\t\t struct file file, unsigned int flags, umode_t mode)\n--\nfs/9p/vfs_inode.c=1370=static const struct inode_operations v9fs_dir_inode_operations_dotu = {\n--\nfs/9p/vfs_inode.c-1372-\t.lookup = v9fs_vfs_lookup,\nfs/9p/vfs_inode.c:1373:\t.atomic_open = v9fs_vfs_atomic_open,\nfs/9p/vfs_inode.c-1374-\t.symlink = v9fs_vfs_symlink,\n--\nfs/9p/vfs_inode.c-1376-\t.unlink = v9fs_vfs_unlink,\nfs/9p/vfs_inode.c:1377:\t.mkdir = v9fs_vfs_mkdir,\nfs/9p/vfs_inode.c-1378-\t.rmdir = v9fs_vfs_rmdir,\n--\nfs/9p/vfs_inode.c=1385=static const struct inode_operations v9fs_dir_inode_operations = {\n--\nfs/9p/vfs_inode.c-1387-\t.lookup = v9fs_vfs_lookup,\nfs/9p/vfs_inode.c:1388:\t.atomic_open = v9fs_vfs_atomic_open,\nfs/9p/vfs_inode.c-1389-\t.unlink = v9fs_vfs_unlink,\nfs/9p/vfs_inode.c:1390:\t.mkdir = v9fs_vfs_mkdir,\nfs/9p/vfs_inode.c-1391-\t.rmdir = v9fs_vfs_rmdir,\n--\nfs/9p/vfs_inode_dotl.c=225=static int\nfs/9p/vfs_inode_dotl.c:226:v9fs_vfs_atomic_open_dotl(struct inode dir, struct dentry dentry,\nfs/9p/vfs_inode_dotl.c-227-\t\t\t struct file file, unsigned int flags, umode_t omode)\n--\nfs/9p/vfs_inode_dotl.c-343-/*\nfs/9p/vfs_inode_dotl.c:344: v9fs_vfs_mkdir_dotl - VFS mkdir hook to create a directory\nfs/9p/vfs_inode_dotl.c-345- * @idmap: The idmap of the mount\n--\nfs/9p/vfs_inode_dotl.c-351-\nfs/9p/vfs_inode_dotl.c:352:static struct dentry v9fs_vfs_mkdir_dotl(struct mnt_idmap idmap,\nfs/9p/vfs_inode_dotl.c-353-\t\t\t\t\t struct inode dir, struct dentry dentry,\n--\nfs/9p/vfs_inode_dotl.c=966=const struct inode_operations v9fs_dir_inode_operations_dotl = {\nfs/9p/vfs_inode_dotl.c-967-\t.create = v9fs_vfs_create_dotl,\nfs/9p/vfs_inode_dotl.c:968:\t.atomic_open = v9fs_vfs_atomic_open_dotl,\nfs/9p/vfs_inode_dotl.c-969-\t.lookup = v9fs_vfs_lookup,\n--\nfs/9p/vfs_inode_dotl.c-972-\t.unlink = v9fs_vfs_unlink,\nfs/9p/vfs_inode_dotl.c:973:\t.mkdir = v9fs_vfs_mkdir_dotl,\nfs/9p/vfs_inode_dotl.c-974-\t.rmdir = v9fs_vfs_rmdir,\n--\nfs/bad_inode.c=136=static int bad_inode_update_time(struct inode inode, enum fs_update_time type,\n--\nfs/bad_inode.c-141-\nfs/bad_inode.c:142:static int bad_inode_atomic_open(struct inode inode, struct dentry dentry,\nfs/bad_inode.c-143-\t\t\t\t struct file file, unsigned int open_flag,\n--\nfs/bad_inode.c=163=static const struct inode_operations bad_inode_ops =\n--\nfs/bad_inode.c-182-\t.update_time\t= bad_inode_update_time,\nfs/bad_inode.c:183:\t.atomic_open\t= bad_inode_atomic_open,\nfs/bad_inode.c-184-\t.tmpfile\t= bad_inode_tmpfile,\n--\nfs/btrfs/ioctl.c=757=static int create_snapshot(struct btrfs_root root, struct inode dir,\n--\nfs/btrfs/ioctl.c-877- * Create a new subvolume below @parent. This is largely modeled after\nfs/btrfs/ioctl.c:878: * sys_mkdirat and vfs_mkdir, but we only do a single component lookup\nfs/btrfs/ioctl.c-879- * inside this filesystem so it's quite a bit simpler.\n--\nfs/cachefiles/namei.c=84=struct dentry cachefiles_get_directory(struct cachefiles_cache cache,\n--\nfs/cachefiles/namei.c-131-\t\tif (ret == 0) {\nfs/cachefiles/namei.c:132:\t\t\tsubdir = vfs_mkdir(\u0026nop_mnt_idmap, d_inode(dir), subdir, 0700, NULL);\nfs/cachefiles/namei.c-133-\t\t\tif (IS_ERR(subdir))\n--\nfs/ceph/dir.c=2255=const struct inode_operations ceph_dir_iops = {\n--\nfs/ceph/dir.c-2270-\t.create = ceph_create,\nfs/ceph/dir.c:2271:\t.atomic_open = ceph_atomic_open,\nfs/ceph/dir.c-2272-};\n--\nfs/ceph/file.c=672=static int ceph_finish_async_create(struct inode dir, struct inode inode,\n--\nfs/ceph/file.c-794- /\nfs/ceph/file.c:795:int ceph_atomic_open(struct inode dir, struct dentry dentry,\nfs/ceph/file.c-796-\t\t struct file file, unsigned flags, umode_t mode)\n--\nfs/ceph/file.c-826-\t/\nfs/ceph/file.c:827:\t Do not truncate the file, since atomic_open is called before the\nfs/ceph/file.c-828-\t * permission check. The caller will do the truncation afterward.\n--\nfs/ceph/super.h=1395=extern int ceph_open(struct inode inode, struct file file);\nfs/ceph/super.h:1396:extern int ceph_atomic_open(struct inode dir, struct dentry dentry,\nfs/ceph/super.h-1397-\t\t\t struct file file, unsigned flags, umode_t mode);\n--\nfs/coda/dir.c=169=static struct dentry coda_mkdir(struct mnt_idmap idmap, struct inode dir,\n--\nfs/coda/dir.c-182-\t/\nfs/coda/dir.c:183:\t vfs_mkdir() now passes S_IFDIR in @mode, but @mode is forwarded\nfs/coda/dir.c-184-\t * verbatim to userspace, which has only ever been given the permission\n--\nfs/configfs/dir.c=673=static void detach_groups(struct dentry dentry)\n--\nfs/configfs/dir.c-709- We could, perhaps, tweak our parent's -\u003emkdir for a minute and\nfs/configfs/dir.c:710: * try using vfs_mkdir. Just a thought.\nfs/configfs/dir.c-711- /\n--\nfs/crypto/hooks.c=131=EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);\n--\nfs/crypto/hooks.c-137- \nfs/crypto/hooks.c:138: * This function should be used by the -\u003elookup and -\u003eatomic_open methods of\nfs/crypto/hooks.c-139- * filesystems that handle filename encryption and no-key name encoding\n--\nfs/dcache.c=3238=struct dentry d_splice_alias_ops(struct inode inode, struct dentry dentry,\n--\nfs/dcache.c-3314- In that case, we know that the inode will be a regular file, and also this\nfs/dcache.c:3315: * will only occur during atomic_open. So we need to check for the dentry\nfs/dcache.c-3316- * being already hashed only in the final case.\n--\nfs/ecryptfs/inode.c=506=static struct dentry ecryptfs_mkdir(struct mnt_idmap idmap, struct inode dir,\n--\nfs/ecryptfs/inode.c-518-\tlower_dir = lower_dir_dentry-\u003ed_inode;\nfs/ecryptfs/inode.c:519:\tlower_dentry = vfs_mkdir(\u0026nop_mnt_idmap, lower_dir,\nfs/ecryptfs/inode.c-520-\t\t\t\t lower_dentry, mode, NULL);\n--\nfs/exec.c=761=EXPORT_SYMBOL(transfer_args_to_stack);\n--\nfs/exec.c-768- /\nfs/exec.c:769:static struct file do_open_execat(int fd, struct filename name, int flags)\nfs/exec.c-770-{\n--\nfs/exec.c-814- \nfs/exec.c:815: As this is a wrapper for the internal do_open_execat(), callers\nfs/exec.c-816- * must call exe_file_allow_write_access() before fput() on release. Also see\n--\nfs/exec.c=819=struct file open_exec(const char name)\n--\nfs/exec.c-821-\tCLASS(filename_kernel, filename)(name);\nfs/exec.c:822:\treturn do_open_execat(AT_FDCWD, filename, 0);\nfs/exec.c-823-}\n--\nfs/exec.c=1408=static int prepare_bprm_creds(struct linux_binprm bprm)\n--\nfs/exec.c-1420-\nfs/exec.c:1421:/ Matches do_open_execat() /\nfs/exec.c-1422-static void do_close_execat(struct file file)\n--\nfs/exec.c=1496=static struct linux_binprm alloc_bprm(int fd, struct filename filename, int flags)\n--\nfs/exec.c-1501-\nfs/exec.c:1502:\tfile = do_open_execat(fd, filename, flags);\nfs/exec.c-1503-\tif (IS_ERR(file))\n--\nfs/fuse/cuse.c=116=static int cuse_open(struct inode inode, struct file file)\n--\nfs/fuse/cuse.c-139-\t /\nfs/fuse/cuse.c:140:\trc = fuse_do_open(\u0026cc-\u003efm, 0, file, 0);\nfs/fuse/cuse.c-141-\tif (rc)\n--\nfs/fuse/dir.c=937=static int fuse_mknod(struct mnt_idmap , struct inode , struct dentry ,\nfs/fuse/dir.c-938-\t\t umode_t, dev_t);\nfs/fuse/dir.c:939:static int fuse_atomic_open(struct inode dir, struct dentry entry,\nfs/fuse/dir.c-940-\t\t\t struct file file, unsigned flags,\n--\nfs/fuse/dir.c=1124=static struct dentry fuse_mkdir(struct mnt_idmap idmap, struct inode dir,\n--\nfs/fuse/dir.c-1134-\t/\nfs/fuse/dir.c:1135:\t vfs_mkdir() now passes S_IFDIR in @mode, but @mode is forwarded\nfs/fuse/dir.c-1136-\t * verbatim to the userspace server which has only ever been given the\n--\nfs/fuse/dir.c=1905=static int fuse_dir_open(struct inode inode, struct file file)\n--\nfs/fuse/dir.c-1916-\nfs/fuse/dir.c:1917:\terr = fuse_do_open(fm, get_node_id(inode), file, true);\nfs/fuse/dir.c-1918-\tif (!err) {\n--\nfs/fuse/dir.c=2420=static const struct inode_operations fuse_dir_inode_operations = {\n--\nfs/fuse/dir.c-2429-\t.create\t\t= fuse_create,\nfs/fuse/dir.c:2430:\t.atomic_open\t= fuse_atomic_open,\nfs/fuse/dir.c-2431-\t.tmpfile\t= fuse_tmpfile,\n--\nfs/fuse/file.c=133=struct fuse_file fuse_file_open(struct fuse_mount fm, u64 nodeid,\n--\nfs/fuse/file.c-188-\nfs/fuse/file.c:189:int fuse_do_open(struct fuse_mount fm, u64 nodeid, struct file file,\nfs/fuse/file.c-190-\t\t bool isdir)\n--\nfs/fuse/file.c-198-}\nfs/fuse/file.c:199:EXPORT_SYMBOL_GPL(fuse_do_open);\nfs/fuse/file.c-200-\n--\nfs/fuse/file.c=250=static int fuse_open(struct inode inode, struct file file)\n--\nfs/fuse/file.c-280-\nfs/fuse/file.c:281:\terr = fuse_do_open(fm, get_node_id(inode), file, false);\nfs/fuse/file.c-282-\tif (!err) {\n--\nfs/fuse/fuse_i.h=1164=void fuse_try_prune_one_inode(struct fuse_conn fc, u64 nodeid);\nfs/fuse/fuse_i.h-1165-\nfs/fuse/fuse_i.h:1166:int fuse_do_open(struct fuse_mount fm, u64 nodeid, struct file file,\nfs/fuse/fuse_i.h-1167-\t\t bool isdir);\n--\nfs/gfs2/file.c=591=static int gfs2_mmap(struct file file, struct vm_area_struct vma)\n--\nfs/gfs2/file.c-613-/\nfs/gfs2/file.c:614: gfs2_open_common - This is common to open and atomic_open\nfs/gfs2/file.c-615- * @inode: The inode being opened\n--\nfs/gfs2/file.c=626=int gfs2_open_common(struct inode inode, struct file file)\n--\nfs/gfs2/file.c-665- \nfs/gfs2/file.c:666: After atomic_open, this function is only used for opening files\nfs/gfs2/file.c-667- * which are already cached. We must still get the glock for regular\n--\nfs/gfs2/inode.c=1366=static int gfs2_mknod(struct mnt_idmap idmap, struct inode dir,\n--\nfs/gfs2/inode.c-1372-/*\nfs/gfs2/inode.c:1373: gfs2_atomic_open - Atomically open a file\nfs/gfs2/inode.c-1374- * @dir: The directory\n--\nfs/gfs2/inode.c-1382-\nfs/gfs2/inode.c:1383:static int gfs2_atomic_open(struct inode dir, struct dentry dentry,\nfs/gfs2/inode.c-1384-\t\t\t struct file file, unsigned flags,\n--\nfs/gfs2/inode.c=2312=static const struct inode_operations gfs2_dir_iops = {\n--\nfs/gfs2/inode.c-2329-\t.update_time = gfs2_update_time,\nfs/gfs2/inode.c:2330:\t.atomic_open = gfs2_atomic_open,\nfs/gfs2/inode.c-2331-\t.fileattr_get = gfs2_fileattr_get,\n--\nfs/internal.h=198=extern struct open_how build_open_how(int flags, umode_t mode);\nfs/internal.h:199:extern int build_open_flags(const struct open_how how, struct open_flags op);\nfs/internal.h-200-struct file file_close_fd_locked(struct files_struct files, unsigned fd);\n--\nfs/namei.c=4342=static inline int open_to_namei_flags(int flag)\n--\nfs/namei.c-4348-\nfs/namei.c:4349:static int may_o_create(struct mnt_idmap idmap,\nfs/namei.c-4350-\t\t\tconst struct path dir, struct dentry dentry,\n--\nfs/namei.c=4381=static inline umode_t o_create_mode(struct mnt_idmap idmap,\n--\nfs/namei.c-4390-/\nfs/namei.c:4391: atomic_open() - atomically look up, create and open a file\nfs/namei.c-4392- * @path: parent directory path\nfs/namei.c:4393: * @dentry: child to -\u003eatomic_open()\nfs/namei.c-4394- * @file: file to attach child to\n--\nfs/namei.c-4396- * @mode: create mode\nfs/namei.c:4397: * @create_error: return value from may_o_create()\nfs/namei.c-4398- \n--\nfs/namei.c-4406- \nfs/namei.c:4407: * FMODE_CREATED is set when the call to -\u003eatomic_open() actually created\nfs/namei.c-4408- * the file.\n--\nfs/namei.c-4412- /\nfs/namei.c:4413:static struct dentry atomic_open(const struct path path, struct dentry dentry,\nfs/namei.c-4414-\t\t\t\t struct file file,\n--\nfs/namei.c-4423-\nfs/namei.c:4424:\terror = dir_inode-\u003ei_op-\u003eatomic_open(dir_inode, dentry, file,\nfs/namei.c-4425-\t\t\t\t\t open_to_namei_flags(open_flag), mode);\n--\nfs/namei.c-4449-\nfs/namei.c:4450:\t\t\tWARN(1, \"%s: -\u003eatomic_open() left file-\u003ef_path.dentry unset!\\n\",\nfs/namei.c-4451-\t\t\t fsname);\n--\nfs/namei.c-4471-\t\t\t continues as a lookup. We can't simply return\nfs/namei.c:4472:\t\t\t * -EOPNOTSUPP from unsupported -\u003eatomic_open()\nfs/namei.c-4473-\t\t\t * implementations because the dentry might be in the\nfs/namei.c:4474:\t\t\t * dcache. In that case, lookup_open() returns before\nfs/namei.c:4475:\t\t\t * reaching -\u003eatomic_open(), and hence whether you get\nfs/namei.c-4476-\t\t\t * -EOPNOTSUPP on O_CREAT\|O_DIRECTORY would not only\n--\nfs/namei.c=4501=static inline\nfs/namei.c:4502:struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry ,\nfs/namei.c-4503-\t\t\t\t umode_t, struct delegated_inode );\n--\nfs/namei.c-4517- /\nfs/namei.c:4518:static struct dentry lookup_open(struct nameidata nd, struct file file,\nfs/namei.c-4519-\t\t\t\t const struct open_flags op)\n--\nfs/namei.c-4575-\tif (dentry-\u003ed_inode) {\nfs/namei.c:4576:\t\t/* Cached positive dentry: will open in do_open(). /\nfs/namei.c-4577-\t\tgoto out;\n--\nfs/namei.c-4599-\t\tif (likely(got_write))\nfs/namei.c:4600:\t\t\tcreate_error = may_o_create(idmap, \u0026nd-\u003epath,\nfs/namei.c-4601-\t\t\t\t\t\t dentry, open_flag, mode);\n--\nfs/namei.c-4611-\t\topen_flag \u0026= ~O_CREAT;\nfs/namei.c:4612:\tif (dir_inode-\u003ei_op-\u003eatomic_open) {\nfs/namei.c-4613-\t\tif (nd-\u003eflags \u0026 LOOKUP_DIRECTORY)\nfs/namei.c-4614-\t\t\topen_flag \|= O_DIRECTORY;\nfs/namei.c:4615:\t\tdentry = atomic_open(\u0026nd-\u003epath, dentry, file, open_flag, mode,\nfs/namei.c-4616-\t\t\t\t create_error);\n--\nfs/namei.c-4636-\t\t No need to create a file. If lookup returned a positive\nfs/namei.c:4637:\t\t * dentry, the file will be opened in do_open().\nfs/namei.c-4638-\t\t /\n--\nfs/namei.c-4657-\tif (create_dir) {\nfs/namei.c:4658:\t\tstruct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode,\nfs/namei.c-4659-\t\t\t\t\t\t \u0026delegated_inode);\n--\nfs/namei.c-4696-/*\nfs/namei.c:4697: vfs_lookup_open - open and possibly create a regular file\nfs/namei.c-4698- * @parent: directory to contain file\n--\nfs/namei.c-4705- * nfsd.\nfs/namei.c:4706: * It uses -\u003eatomic_open or -\u003elookup / -\u003ecreate / -\u003eopen as appropriate.\nfs/namei.c-4707- \n--\nfs/namei.c-4714- -EFTYPE : any other non-regular file was found, such as FIFO or SOCK.\nfs/namei.c:4715: * or -\u003eatomic_open responded to __O_REGULAR.\nfs/namei.c-4716- \n--\nfs/namei.c-4718- /\nfs/namei.c:4719:struct file vfs_lookup_open(struct path parent, struct qstr last,\nfs/namei.c-4720-\t\t\t int open_flag, umode_t mode)\n--\nfs/namei.c-4752-\top.mode = mode;\nfs/namei.c:4753:\tdentry = lookup_open(\u0026nd, file, \u0026op);\nfs/namei.c-4754-\n--\nfs/namei.c-4789-}\nfs/namei.c:4790:EXPORT_SYMBOL_FOR_MODULES(vfs_lookup_open, \"nfsd\");\nfs/namei.c-4791-\n--\nfs/namei.c=4823=static const char open_last_lookups(struct nameidata nd,\n--\nfs/namei.c-4855-\nfs/namei.c:4856:\tdentry = lookup_open(nd, file, op);\nfs/namei.c-4857-\tif (IS_ERR(dentry))\n--\nfs/namei.c-4877- /\nfs/namei.c:4878:static int do_open(struct nameidata nd,\nfs/namei.c-4879-\t\t struct file file, const struct open_flags op)\n--\nfs/namei.c=4956=int vfs_tmpfile(struct mnt_idmap idmap,\n--\nfs/namei.c-4965-\nfs/namei.c:4966:\t/* A tmpfile is I_LINKABLE, so guard its owner like may_o_create(). /\nfs/namei.c-4967-\tif (!fsuidgid_has_mapping(dir-\u003ei_sb, idmap))\n--\nfs/namei.c=5070=static struct file path_openat(struct nameidata nd,\n--\nfs/namei.c-5089-\t\tif (!error)\nfs/namei.c:5090:\t\t\terror = do_open(nd, file, op);\nfs/namei.c-5091-\t\tterminate_walk(nd);\n--\nfs/namei.c=5207=EXPORT_SYMBOL(start_creating_path);\n--\nfs/namei.c-5216- if start_creating_path() returned a non-error.\nfs/namei.c:5217: * If vfs_mkdir() was called and it returned an error, that error should\nfs/namei.c-5218- * be passed to end_creating_path() together with the path.\n--\nfs/namei.c=5254=struct file dentry_create(struct path path, int flags, umode_t mode,\n--\nfs/namei.c-5270-\nfs/namei.c:5271:\tif (dir_inode-\u003ei_op-\u003eatomic_open) {\nfs/namei.c-5272-\t\tpath-\u003edentry = dir;\n--\nfs/namei.c-5274-\nfs/namei.c:5275:\t\tcreate_error = may_o_create(idmap, path, dentry, flags, mode);\nfs/namei.c-5276-\t\tif (create_error)\n--\nfs/namei.c-5278-\nfs/namei.c:5279:\t\t/* atomic_open will dput(dentry) on error /\nfs/namei.c-5280-\t\tdget(orig_dentry);\nfs/namei.c:5281:\t\tdentry = atomic_open(path, dentry, file, flags, mode, create_error);\nfs/namei.c-5282-\t\terror = PTR_ERR_OR_ZERO(dentry);\n--\nfs/namei.c=5442=static inline\nfs/namei.c:5443:struct dentry vfs_mkdir_no_perm(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c-5444-\t\t\t\t struct dentry dentry, umode_t mode,\n--\nfs/namei.c-5469-/\nfs/namei.c:5470: vfs_mkdir - create directory returning correct dentry if possible\nfs/namei.c-5471- * @idmap:\t\tidmap of the mount the inode was found from\n--\nfs/namei.c-5490- /\nfs/namei.c:5491:struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c-5492-\t\t\t struct dentry dentry, umode_t mode,\n--\nfs/namei.c-5510-\nfs/namei.c:5511:\tde = vfs_mkdir_no_perm(idmap, dir, dentry, mode, delegated_inode);\nfs/namei.c-5512-\tif (IS_ERR(de)) {\n--\nfs/namei.c-5521-}\nfs/namei.c:5522:EXPORT_SYMBOL(vfs_mkdir);\nfs/namei.c-5523-\nfs/namei.c=5524=int filename_mkdirat(int dfd, struct filename name, umode_t mode)\n--\nfs/namei.c-5539-\tif (!error) {\nfs/namei.c:5540:\t\tdentry = vfs_mkdir(mnt_idmap(path.mnt), path.dentry-\u003ed_inode,\nfs/namei.c-5541-\t\t\t\t dentry, mode, \u0026delegated_inode);\n--\nfs/nfs/dir.c=1854=static void block_revalidate(struct dentry dentry)\n--\nfs/nfs/dir.c-1859-\t/ Any new reference that could lead to an open\nfs/nfs/dir.c:1860:\t * will take -\u003ed_lock in lookup_open() -\u003e d_lookup().\nfs/nfs/dir.c-1861-\t * Holding this lock ensures we cannot race with\n--\nfs/nfs/dir.c=2076=static struct nfs_open_context create_nfs_open_context(struct dentry dentry, int open_flags, struct file filp)\n--\nfs/nfs/dir.c-2080-\nfs/nfs/dir.c:2081:static int do_open(struct inode inode, struct file filp)\nfs/nfs/dir.c-2082-{\n--\nfs/nfs/dir.c=2087=static int nfs_finish_open(struct nfs_open_context ctx,\n--\nfs/nfs/dir.c-2092-\nfs/nfs/dir.c:2093:\terr = finish_open(file, dentry, do_open);\nfs/nfs/dir.c-2094-\tif (err)\n--\nfs/nfs/dir.c-2103-\nfs/nfs/dir.c:2104:int nfs_atomic_open(struct inode dir, struct dentry dentry,\nfs/nfs/dir.c-2105-\t\t struct file file, unsigned open_flags,\n--\nfs/nfs/dir.c-2120-\nfs/nfs/dir.c:2121:\tdfprintk(VFS, \"NFS: atomic_open(%s/%llu), %pd\\n\",\nfs/nfs/dir.c-2122-\t\t\tdir-\u003ei_sb-\u003es_id, dir-\u003ei_ino, dentry);\n--\nfs/nfs/dir.c-2179-\nfs/nfs/dir.c:2180:\ttrace_nfs_atomic_open_enter(dir, ctx, open_flags);\nfs/nfs/dir.c-2181-\tinode = NFS_PROTO(dir)-\u003eopen_context(dir, ctx, open_flags, \u0026attr, \u0026created);\n--\nfs/nfs/dir.c-2185-\t\terr = PTR_ERR(inode);\nfs/nfs/dir.c:2186:\t\ttrace_nfs_atomic_open_exit(dir, ctx, open_flags, err);\nfs/nfs/dir.c-2187-\t\tput_nfs_open_context(ctx);\n--\nfs/nfs/dir.c-2221-\terr = nfs_finish_open(ctx, ctx-\u003edentry, file, open_flags);\nfs/nfs/dir.c:2222:\ttrace_nfs_atomic_open_exit(dir, ctx, open_flags, err);\nfs/nfs/dir.c-2223-\tput_nfs_open_context(ctx);\n--\nfs/nfs/dir.c-2259-}\nfs/nfs/dir.c:2260:EXPORT_SYMBOL_GPL(nfs_atomic_open);\nfs/nfs/dir.c-2261-\n--\nfs/nfs/dir.c=2263=nfs4_lookup_revalidate(struct inode dir, const struct qstr name,\n--\nfs/nfs/dir.c-2314-\nfs/nfs/dir.c:2315:int nfs_atomic_open_v23(struct inode dir, struct dentry dentry,\nfs/nfs/dir.c-2316-\t\t\tstruct file file, unsigned int open_flags,\n--\nfs/nfs/dir.c-2319-\tstruct dentry res = NULL;\nfs/nfs/dir.c:2320:\t/ Same as look+open from lookup_open(), but with different O_TRUNC\nfs/nfs/dir.c-2321-\t * handling.\n--\nfs/nfs/dir.c-2357-}\nfs/nfs/dir.c:2358:EXPORT_SYMBOL_GPL(nfs_atomic_open_v23);\nfs/nfs/dir.c-2359-\n--\nfs/nfs/nfs3proc.c=1042=static const struct inode_operations nfs3_dir_inode_operations = {\nfs/nfs/nfs3proc.c-1043-\t.create\t\t= nfs_create,\nfs/nfs/nfs3proc.c:1044:\t.atomic_open\t= nfs_atomic_open_v23,\nfs/nfs/nfs3proc.c-1045-\t.lookup\t\t= nfs_lookup,\n--\nfs/nfs/nfs4_fs.h=282=extern const struct dentry_operations nfs4_dentry_operations;\n--\nfs/nfs/nfs4_fs.h-284-/* dir.c /\nfs/nfs/nfs4_fs.h:285:int nfs_atomic_open(struct inode , struct dentry , struct file ,\nfs/nfs/nfs4_fs.h-286-\t\t unsigned, umode_t);\n--\nfs/nfs/nfs4proc.c=1275=struct nfs4_open_createattrs {\n--\nfs/nfs/nfs4proc.c-1280-\nfs/nfs/nfs4proc.c:1281:static bool nfs4_clear_cap_atomic_open_v1(struct nfs_server server,\nfs/nfs/nfs4proc.c-1282-\t\tint err, struct nfs4_exception exception)\n--\nfs/nfs/nfs4proc.c=1323=static u32\nfs/nfs/nfs4proc.c:1324:nfs4_map_atomic_open_share(struct nfs_server server,\nfs/nfs/nfs4proc.c-1325-\t\tfmode_t fmode, int openflags)\n--\nfs/nfs/nfs4proc.c=1345=static enum open_claim_type4\nfs/nfs/nfs4proc.c:1346:nfs4_map_atomic_open_claim(struct nfs_server server,\nfs/nfs/nfs4proc.c-1347-\t\tenum open_claim_type4 claim)\n--\nfs/nfs/nfs4proc.c=1374=static struct nfs4_opendata nfs4_opendata_alloc(struct dentry dentry,\n--\nfs/nfs/nfs4proc.c-1409-\tp-\u003eo_arg.fmode = fmode \u0026 (FMODE_READ\|FMODE_WRITE);\nfs/nfs/nfs4proc.c:1410:\tp-\u003eo_arg.claim = nfs4_map_atomic_open_claim(server, claim);\nfs/nfs/nfs4proc.c:1411:\tp-\u003eo_arg.share_access = nfs4_map_atomic_open_share(server,\nfs/nfs/nfs4proc.c-1412-\t\t\tfmode, flags);\n--\nfs/nfs/nfs4proc.c=2180=static int nfs4_open_recover_helper(struct nfs4_opendata *opendata,\n--\nfs/nfs/nfs4proc.c-2191-\topendata-\u003eo_arg.share_access =\nfs/nfs/nfs4proc.c:2192:\t\tnfs4_map_atomic_open_share(server, fmode, openflags);\n\n" }
5/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28861 output: 27 thoughts: 27 Thoughts: Here's a summary of my thought process, as requested: Deconstructing File Open Flags Okay, so I need to understand how the `build_open_flags` function is being used within the kernel. My initial thought is to dive into `fs/open.c` directly. Line 1239 seems like a likely starting point – it's a specific area I'm targeting within the module. From there, I'll trace back which functions are calling `build_open_flags`. The goal is to see exactly how these open flags are being constructed. I want to see which specific scenarios that `build_open_flags` function will come in to play. I'll need to follow the control flow to get a good understanding. I need to understand the big picture of what's going on.
6/2	2026/09/13 19:51	tool	grepper	0m Args: { "Expression": "build_open_flags", "PathPrefix": "fs/" } Results: { "Output": "fs/internal.h=198=extern struct open_how build_open_how(int flags, umode_t mode);\nfs/internal.h:199:extern int build_open_flags(const struct open_how how, struct open_flags op);\nfs/internal.h-200-struct file file_close_fd_locked(struct files_struct files, unsigned fd);\n--\nfs/open.c=1185=inline struct open_how build_open_how(int flags, umode_t mode)\n--\nfs/open.c-1200-\nfs/open.c:1201:inline int build_open_flags(const struct open_how how, struct open_flags op)\nfs/open.c-1202-{\n--\nfs/open.c-1225-\t * Older syscalls implicitly clear all of the invalid flags or argument\nfs/open.c:1226:\t * values before calling build_open_flags(), but openat2(2) checks all\nfs/open.c-1227-\t * of its arguments.\n--\nfs/open.c=1378=struct file file_open_name(struct filename name, int flags, umode_t mode)\n--\nfs/open.c-1381-\tstruct open_how how = build_open_how(flags, mode);\nfs/open.c:1382:\tint err = build_open_flags(\u0026how, \u0026op);\nfs/open.c-1383-\tif (err)\n--\nfs/open.c=1406=struct file file_open_root(const struct path root,\n--\nfs/open.c-1410-\tstruct open_how how = build_open_how(flags, mode);\nfs/open.c:1411:\tint err = build_open_flags(\u0026how, \u0026op);\nfs/open.c-1412-\tif (err)\n--\nfs/open.c=1418=static int do_sys_openat2(int dfd, const char __user *filename,\n--\nfs/open.c-1421-\tstruct open_flags op;\nfs/open.c:1422:\tint err = build_open_flags(how, \u0026op);\nfs/open.c-1423-\tif (unlikely(err))\n" }
7/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29690 output: 34 thoughts: 62 Thoughts: Okay, here's my take on those thoughts, framed as my own mental process, given my expertise: Diving into the Open System Call Implementation Alright, so I'm focusing in on the `do_sys_openat2` function, specifically within `fs/open.c`. Right, that's the central point of entry, the one handling all those newer open system calls, including the original `sys_open`, the `sys_openat` variant and, most importantly here, the more recent `sys_openat2`. I need to understand how the kernel actually handles file opening, creation, and the nuanced flags and attributes. Given that it's the `at2` version, it likely contains the more modern and flexible features. This means it'll be critical to see how the system handles the potentially complex arguments and attribute structures for `sys_openat2` and how it interacts with the underlying VFS layer. Let's delve into that function and understand its flow.
8/2	2026/09/13 19:51	tool	read-file	0m Args: { "File": "fs/open.c", "FirstLine": 1418, "LineCount": 40 } Results: { "Contents": "1418:\tstatic int do_sys_openat2(int dfd, const char __user filename,\n1419:\t\t\t\t struct open_how how)\n1420:\t{\n1421:\t\tstruct open_flags op;\n1422:\t\tint err = build_open_flags(how, \u0026op);\n1423:\t\tif (unlikely(err))\n1424:\t\t\treturn err;\n1425:\t\n1426:\t\tCLASS(filename_flags, name)(filename, op.lookup_flags);\n1427:\t\treturn FD_ADD(how-\u003eflags, do_file_open(dfd, name, \u0026op));\n1428:\t}\n1429:\t\n1430:\tint do_sys_open(int dfd, const char __user filename, int flags, umode_t mode)\n1431:\t{\n1432:\t\tstruct open_how how = build_open_how(flags, mode);\n1433:\t\treturn do_sys_openat2(dfd, filename, \u0026how);\n1434:\t}\n1435:\t\n1436:\t\n1437:\tSYSCALL_DEFINE3(open, const char __user , filename, int, flags, umode_t, mode)\n1438:\t{\n1439:\t\tif (force_o_largefile())\n1440:\t\t\tflags \|= O_LARGEFILE;\n1441:\t\treturn do_sys_open(AT_FDCWD, filename, flags, mode);\n1442:\t}\n1443:\t\n1444:\tSYSCALL_DEFINE4(openat, int, dfd, const char __user , filename, int, flags,\n1445:\t\t\tumode_t, mode)\n1446:\t{\n1447:\t\tif (force_o_largefile())\n1448:\t\t\tflags \|= O_LARGEFILE;\n1449:\t\treturn do_sys_open(dfd, filename, flags, mode);\n1450:\t}\n1451:\t\n1452:\tSYSCALL_DEFINE4(openat2, int, dfd, const char __user , filename,\n1453:\t\t\tstruct open_how __user *, how, size_t, usize)\n1454:\t{\n1455:\t\tint err;\n1456:\t\tstruct open_how tmp;\n1457:\t\n" }
9/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30632 output: 27 thoughts: 23 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Diving into the `do_file_open` Call Stack Okay, let's trace this `do_file_open` call and see how it dances its way down into `fs/namei.c`. I'm particularly interested in seeing how the path resolution works, any potential lookups using a cache, and what kind of error checking is happening at each stage. I'll need to pay close attention to the data structures involved, like the `path` structure, and how inode numbers and dentry objects are being used to map between the logical file name and the physical location on the storage device. My goal is to determine if I can identify a potential performance bottleneck here, maybe related to a particular filesystem type or some specific access pattern that I am familiar with, and consider what possible optimizations can be applied. I'll also be watching for any potential security vulnerabilities in the path traversal logic – always a concern when dealing with open systems and user-provided paths.
10/2	2026/09/13 19:51	tool	grepper	0m Args: { "Expression": "do_file_open", "PathPrefix": "fs/" } Results: { "Output": "fs/exec.c=769=static struct file do_open_execat(int fd, struct filename name, int flags)\n--\nfs/exec.c-785-\nfs/exec.c:786:\tfile = do_file_open(fd, name, \u0026open_exec_flags);\nfs/exec.c-787-\tif (IS_ERR(file))\n--\nfs/internal.h=187=struct open_flags {\n--\nfs/internal.h-193-};\nfs/internal.h:194:extern struct file do_file_open(int dfd, struct filename pathname,\nfs/internal.h-195-\t\tconst struct open_flags op);\nfs/internal.h:196:extern struct file do_file_open_root(const struct path ,\nfs/internal.h-197-\t\tconst char , const struct open_flags );\n--\nfs/namei.c=5070=static struct file path_openat(struct nameidata nd,\n--\nfs/namei.c-5108-\nfs/namei.c:5109:struct file do_file_open(int dfd, struct filename pathname,\nfs/namei.c-5110-\t\tconst struct open_flags op)\n--\nfs/namei.c-5127-\nfs/namei.c:5128:struct file do_file_open_root(const struct path root,\nfs/namei.c-5129-\t\tconst char name, const struct open_flags op)\n--\nfs/open.c=1378=struct file file_open_name(struct filename name, int flags, umode_t mode)\n--\nfs/open.c-1384-\t\treturn ERR_PTR(err);\nfs/open.c:1385:\treturn do_file_open(AT_FDCWD, name, \u0026op);\nfs/open.c-1386-}\n--\nfs/open.c=1406=struct file file_open_root(const struct path root,\n--\nfs/open.c-1413-\t\treturn ERR_PTR(err);\nfs/open.c:1414:\treturn do_file_open_root(root, filename, \u0026op);\nfs/open.c-1415-}\n--\nfs/open.c=1418=static int do_sys_openat2(int dfd, const char __user *filename,\n--\nfs/open.c-1426-\tCLASS(filename_flags, name)(filename, op.lookup_flags);\nfs/open.c:1427:\treturn FD_ADD(how-\u003eflags, do_file_open(dfd, name, \u0026op));\nfs/open.c-1428-}\n" }
11/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31620 output: 35 thoughts: 76 Thoughts: Here's my take on those steps: Diving into `path_openat` Okay, so I'm digging into `path_openat` in `fs/namei.c`. My immediate thought is, "Right, let's trace this thing." I know from experience that `path_openat` is the workhorse here, so I want to understand its call stack. So, first thing I'm going to do is get my bearings. I'm recalling that I saw that `path_openat` then moves into `open_last_lookups` function, which, I now recall, then calls `lookup_open` and ultimately `do_open`. That's the core flow, and I need to see how these pieces fit. So, I'm going to jump to line 4400 through 4700 in `fs/namei.c`. That should give me the context I need to visualize the logic. I need to see the relationships between these functions, how the arguments are passed, and where the critical decisions are made in order to understand what is going on at the core level.
12/2	2026/09/13 19:51	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4415, "LineCount": 90 } Results: { "Contents": "4415:\t\t\t\t\t int open_flag, umode_t mode, int create_error)\n4416:\t{\n4417:\t\tstruct dentry const DENTRY_NOT_SET = (void ) -1UL;\n4418:\t\tstruct inode dir_inode = path-\u003edentry-\u003ed_inode;\n4419:\t\tint error;\n4420:\t\n4421:\t\tfile-\u003e__f_path.dentry = DENTRY_NOT_SET;\n4422:\t\tfile-\u003e__f_path.mnt = path-\u003emnt;\n4423:\t\n4424:\t\terror = dir_inode-\u003ei_op-\u003eatomic_open(dir_inode, dentry, file,\n4425:\t\t\t\t\t\t open_to_namei_flags(open_flag), mode);\n4426:\t\td_lookup_done(dentry);\n4427:\t\n4428:\t\tif (!error) {\n4429:\t\t\tif (file-\u003ef_mode \u0026 FMODE_OPENED) {\n4430:\t\t\t\t/ finish_open() called /\n4431:\t\t\t\tstruct dentry opened = file-\u003ef_path.dentry;\n4432:\t\n4433:\t\t\t\tif (unlikely(opened != dentry)) {\n4434:\t\t\t\t\tdput(dentry);\n4435:\t\t\t\t\tdentry = dget(opened);\n4436:\t\t\t\t}\n4437:\t\t\t} else if (likely(file-\u003ef_path.dentry != DENTRY_NOT_SET)) {\n4438:\t\t\t\t/* finish_no_open() called /\n4439:\t\t\t\tstruct dentry replaced = file-\u003ef_path.dentry;\n4440:\t\n4441:\t\t\t\tif (replaced) {\n4442:\t\t\t\t\tdput(dentry);\n4443:\t\t\t\t\tdentry = replaced;\n4444:\t\t\t\t}\n4445:\t\t\t\tif (unlikely(d_is_negative(dentry)))\n4446:\t\t\t\t\terror = -ENOENT;\n4447:\t\t\t} else {\n4448:\t\t\t\tconst char fsname = dentry-\u003ed_sb-\u003es_type-\u003ename;\n4449:\t\n4450:\t\t\t\tWARN(1, \"%s: -\u003eatomic_open() left file-\u003ef_path.dentry unset!\\n\",\n4451:\t\t\t\t fsname);\n4452:\t\t\t\terror = -EIO;\n4453:\t\t\t}\n4454:\t\t}\n4455:\t\n4456:\t\tif (error) {\n4457:\t\t\tif (unlikely(create_error) \u0026\u0026 error == -ENOENT) {\n4458:\t\t\t\t/\n4459:\t\t\t\t * Should have done a create, but errored before.\n4460:\t\t\t\t * Some filesystems return -ENOENT directly instead of\n4461:\t\t\t\t * calling finish_no_open() with a negative dentry;\n4462:\t\t\t\t * either way it should only mean the child doesn't exist,\n4463:\t\t\t\t * so a refused create is safe to record here.\n4464:\t\t\t\t /\n4465:\t\t\t\taudit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);\n4466:\t\t\t\terror = create_error;\n4467:\t\t\t} else if (O_IS_MKDIR(open_flag) \u0026\u0026 error == -ENOENT) {\n4468:\t\t\t\t/\n4469:\t\t\t\t * If the underlying filesystem does not implement\n4470:\t\t\t\t * O_CREAT\|O_DIRECTORY, it strips the O_CREAT bit and\n4471:\t\t\t\t * continues as a lookup. We can't simply return\n4472:\t\t\t\t * -EOPNOTSUPP from unsupported -\u003eatomic_open()\n4473:\t\t\t\t * implementations because the dentry might be in the\n4474:\t\t\t\t * dcache. In that case, lookup_open() returns before\n4475:\t\t\t\t * reaching -\u003eatomic_open(), and hence whether you get\n4476:\t\t\t\t * -EOPNOTSUPP on O_CREAT\|O_DIRECTORY would not only\n4477:\t\t\t\t * depend on the underlying filesystem, but also on\n4478:\t\t\t\t * the state of the dcache. Still, we must make an\n4479:\t\t\t\t * effort to differentiate a regular -ENOENT from the\n4480:\t\t\t\t * unsupported O_CREAT\|O_DIRECTORY case.\n4481:\t\t\t\t /\n4482:\t\t\t\terror = -EOPNOTSUPP;\n4483:\t\t\t}\n4484:\t\t\tdput(dentry);\n4485:\t\t\tdentry = ERR_PTR(error);\n4486:\t\t} else {\n4487:\t\t\tif (file-\u003ef_mode \u0026 FMODE_CREATED) {\n4488:\t\t\t\tif (d_is_dir(dentry))\n4489:\t\t\t\t\tfsnotify_mkdir(dir_inode, dentry);\n4490:\t\t\t\telse\n4491:\t\t\t\t\tfsnotify_create(dir_inode, dentry);\n4492:\t\t\t}\n4493:\t\t\tif (file-\u003ef_mode \u0026 FMODE_OPENED)\n4494:\t\t\t\tfsnotify_open(file);\n4495:\t\t}\n4496:\t\n4497:\t\n4498:\t\treturn dentry;\n4499:\t}\n4500:\t\n4501:\tstatic inline\n4502:\tstruct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry ,\n4503:\t\t\t\t\t umode_t, struct delegated_inode );\n4504:\t/*\n" }
13/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 33402 output: 35 thoughts: 26 Thoughts: Here's a summary of my thought process, as requested: Diving Deep into File System Operations Okay, I'm already in the thick of this file system code, and my mind is now drawn towards those crucial functions: `lookup_open` and `do_open`. I'm specifically thinking about where they reside within `fs/namei.c`. It's essential I understand how they contribute to the path resolution and file opening process, and how they play together. I need to refresh my understanding of their interaction with the VFS layer.
14/2	2026/09/13 19:51	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4520, "LineCount": 85 } Results: { "Contents": "4520:\t{\n4521:\t\tstruct delegated_inode delegated_inode = { };\n4522:\t\tstruct mnt_idmap idmap;\n4523:\t\tstruct dentry dir = nd-\u003epath.dentry;\n4524:\t\tstruct inode dir_inode = dir-\u003ed_inode;\n4525:\t\tbool create_dir = O_IS_MKDIR(op-\u003eopen_flag);\n4526:\t\tint open_flag;\n4527:\t\tstruct dentry dentry;\n4528:\t\tint error, create_error;\n4529:\t\tumode_t mode;\n4530:\t\tbool got_write;\n4531:\t\n4532:\tretry:\n4533:\t\topen_flag = op-\u003eopen_flag;\n4534:\t\tgot_write = false;\n4535:\t\tmode = op-\u003emode;\n4536:\t\tcreate_error = 0;\n4537:\t\n4538:\t\tif (open_flag \u0026 (O_CREAT \| O_TRUNC \| O_WRONLY \| O_RDWR)) {\n4539:\t\t\tgot_write = !mnt_want_write(nd-\u003epath.mnt);\n4540:\t\t\t/\n4541:\t\t\t do _not_ fail yet - we might not need that or fail with\n4542:\t\t\t * a different error; we'll be dropping this one anyway.\n4543:\t\t\t /\n4544:\t\t}\n4545:\t\tif (open_flag \u0026 O_CREAT)\n4546:\t\t\tinode_lock_nested(dir_inode, I_MUTEX_PARENT);\n4547:\t\telse\n4548:\t\t\tinode_lock_shared(dir_inode);\n4549:\t\n4550:\t\tif (unlikely(IS_DEADDIR(dir_inode))) {\n4551:\t\t\tdentry = ERR_PTR(-ENOENT);\n4552:\t\t\tgoto out;\n4553:\t\t}\n4554:\t\n4555:\t\tfile-\u003ef_mode \u0026= ~FMODE_CREATED;\n4556:\t\tdentry = d_lookup(dir, \u0026nd-\u003elast);\n4557:\t\tfor (;;) {\n4558:\t\t\tif (!dentry) {\n4559:\t\t\t\tdentry = d_alloc_parallel(dir, \u0026nd-\u003elast);\n4560:\t\t\t\tif (IS_ERR(dentry))\n4561:\t\t\t\t\tgoto out;\n4562:\t\t\t}\n4563:\t\t\tif (d_in_lookup(dentry))\n4564:\t\t\t\tbreak;\n4565:\t\n4566:\t\t\terror = d_revalidate(dir_inode, \u0026nd-\u003elast, dentry, nd-\u003eflags);\n4567:\t\t\tif (likely(error \u003e 0))\n4568:\t\t\t\tbreak;\n4569:\t\t\tif (error)\n4570:\t\t\t\tgoto out_dput;\n4571:\t\t\td_invalidate(dentry);\n4572:\t\t\tdput(dentry);\n4573:\t\t\tdentry = NULL;\n4574:\t\t}\n4575:\t\tif (dentry-\u003ed_inode) {\n4576:\t\t\t/ Cached positive dentry: will open in do_open(). /\n4577:\t\t\tgoto out;\n4578:\t\t}\n4579:\t\n4580:\t\tif (open_flag \u0026 O_CREAT)\n4581:\t\t\taudit_inode(nd-\u003ename, dir, AUDIT_INODE_PARENT);\n4582:\t\n4583:\t\t/\n4584:\t\t * Checking write permission is tricky, bacuse we don't know if we are\n4585:\t\t * going to actually need it: O_CREAT opens should work as long as the\n4586:\t\t * file exists. But checking existence breaks atomicity. The trick is\n4587:\t\t * to check access and if not granted clear O_CREAT from the flags.\n4588:\t\t \n4589:\t\t Another problem is returing the \"right\" error value (e.g. for an\n4590:\t\t * O_EXCL open we want to return EEXIST not EROFS).\n4591:\t\t /\n4592:\t\tif (unlikely(!got_write))\n4593:\t\t\topen_flag \u0026= ~O_TRUNC;\n4594:\t\tidmap = mnt_idmap(nd-\u003epath.mnt);\n4595:\t\tif (open_flag \u0026 O_CREAT) {\n4596:\t\t\tif (open_flag \u0026 O_EXCL)\n4597:\t\t\t\topen_flag \u0026= ~O_TRUNC;\n4598:\t\t\tmode = o_create_mode(idmap, dir_inode, open_flag, mode);\n4599:\t\t\tif (likely(got_write))\n4600:\t\t\t\tcreate_error = may_o_create(idmap, \u0026nd-\u003epath,\n4601:\t\t\t\t\t\t\t dentry, open_flag, mode);\n4602:\t\t\telse\n4603:\t\t\t\tcreate_error = -EROFS;\n4604:\t\t\t/ Refuse to create a directory through a dangling (trailing)\n" }
15/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34913 output: 35 thoughts: 26 Thoughts: Okay, here's my attempt at summarizing that section of `fs/namei.c`, presented as a first-person account from an expert's perspective: Diving Back into `fs/namei.c` Alright, time to get back into the weeds and focus on lines 4605 to 4680 within `fs/namei.c`. I know this area intimately; it's where the kernel handles the critical work of pathname resolution. Specifically, I'm expecting to find code related to how the system actually translates user-provided pathnames into usable inodes. This could be anything from handling symbolic links, dealing with mount points, managing directory entries, or error-handling when things aren't quite right. Given the line range, I'm guessing this section could relate to a specific aspect of the lookup process, perhaps a particular optimization, or a more complex scenario involving things like cross-filesystem lookups, or even potentially dealing with things like extended attributes. I'll need to see the code, but my intuition tells me this section likely pertains to a specific edge-case, because the context implies that a range of lines is being highlighted for further review. Knowing this module, I'm expecting this section to be fairly dense, but also very well-commented, as that's generally good practice in this kind of critical system code. Let's dig in and see what's what.
16/2	2026/09/13 19:51	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4605, "LineCount": 80 } Results: { "Contents": "4605:\t\t\t * symlink. For regular files this has been allowed historically\n4606:\t\t\t * on O_CREAT without O_EXCL. /\n4607:\t\t\tif (unlikely(nd-\u003edepth) \u0026\u0026 create_dir \u0026\u0026 !create_error)\n4608:\t\t\t\tcreate_error = -EEXIST;\n4609:\t\t}\n4610:\t\tif (create_error)\n4611:\t\t\topen_flag \u0026= ~O_CREAT;\n4612:\t\tif (dir_inode-\u003ei_op-\u003eatomic_open) {\n4613:\t\t\tif (nd-\u003eflags \u0026 LOOKUP_DIRECTORY)\n4614:\t\t\t\topen_flag \|= O_DIRECTORY;\n4615:\t\t\tdentry = atomic_open(\u0026nd-\u003epath, dentry, file, open_flag, mode,\n4616:\t\t\t\t\t create_error);\n4617:\t\t\tgoto out;\n4618:\t\t}\n4619:\t\n4620:\t\tif (d_in_lookup(dentry)) {\n4621:\t\t\tstruct dentry res = dir_inode-\u003ei_op-\u003elookup(dir_inode, dentry,\n4622:\t\t\t\t\t\t\t\t nd-\u003eflags);\n4623:\t\t\td_lookup_done(dentry);\n4624:\t\t\tif (unlikely(res)) {\n4625:\t\t\t\tif (IS_ERR(res)) {\n4626:\t\t\t\t\terror = PTR_ERR(res);\n4627:\t\t\t\t\tgoto out_dput;\n4628:\t\t\t\t}\n4629:\t\t\t\tdput(dentry);\n4630:\t\t\t\tdentry = res;\n4631:\t\t\t}\n4632:\t\t}\n4633:\t\n4634:\t\tif (dentry-\u003ed_inode \|\| !(op-\u003eopen_flag \u0026 O_CREAT)) {\n4635:\t\t\t/\n4636:\t\t\t No need to create a file. If lookup returned a positive\n4637:\t\t\t * dentry, the file will be opened in do_open().\n4638:\t\t\t /\n4639:\t\t\tgoto out;\n4640:\t\t}\n4641:\t\n4642:\t\t/ Negative dentry with O_CREAT flag set /\n4643:\t\taudit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);\n4644:\t\n4645:\t\tif (unlikely(create_error)) {\n4646:\t\t\t/ should have done a create, but we already errored /\n4647:\t\t\terror = create_error;\n4648:\t\t\tgoto out_dput;\n4649:\t\t}\n4650:\t\n4651:\t\tif ((create_dir \u0026\u0026 !dir_inode-\u003ei_op-\u003emkdir)\n4652:\t\t\t\|\| (!create_dir \u0026\u0026 !dir_inode-\u003ei_op-\u003ecreate)) {\n4653:\t\t\terror = -EOPNOTSUPP;\n4654:\t\t\tgoto out_dput;\n4655:\t\t}\n4656:\t\n4657:\t\tif (create_dir) {\n4658:\t\t\tstruct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode,\n4659:\t\t\t\t\t\t\t \u0026delegated_inode);\n4660:\t\t\terror = PTR_ERR_OR_ZERO(res);\n4661:\t\t\tif (!error)\n4662:\t\t\t\tdentry = res;\n4663:\t\t} else {\n4664:\t\t\terror = vfs_create_no_perm(idmap, dentry, mode, \u0026delegated_inode);\n4665:\t\t}\n4666:\t\tif (error)\n4667:\t\t\tgoto out_dput;\n4668:\t\n4669:\t\tfile-\u003ef_mode \|= FMODE_CREATED;\n4670:\tout:\n4671:\t\tif ((open_flag \u0026 O_CREAT) \|\| create_error)\n4672:\t\t\tinode_unlock(dir_inode);\n4673:\t\telse\n4674:\t\t\tinode_unlock_shared(dir_inode);\n4675:\t\n4676:\t\tif (got_write)\n4677:\t\t\tmnt_drop_write(nd-\u003epath.mnt);\n4678:\t\n4679:\t\tif (is_delegated(\u0026delegated_inode)) {\n4680:\t\t\t/* Must have come through out_dput: dentry is an ERR_PTR() */\n4681:\t\t\terror = break_deleg_wait(\u0026delegated_inode);\n4682:\t\n4683:\t\t\tif (!error)\n4684:\t\t\t\tgoto retry;\n" }
17/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36474 output: 35 thoughts: 20 Thoughts: Here's my take on those thoughts, tailored for an expert audience: Diving into `do_open` in `fs/namei.c` Okay, so we're talking about `do_open` in `fs/namei.c`. That immediately tells me we're dealing with the core of the open system call – the actual mechanics of path resolution and file opening within the kernel's virtual filesystem layer. I know this is where the heavy lifting of security checks, permission verification, and inode allocation (if creating) all happens. I need to refresh my memory on the exact sequence here. We'll be looking at how path components are traversed, how symlinks are handled (recursively, I hope!), and what data structures are involved during the process. This is where race conditions become a concern, and that makes me wonder whether there might be any potential for subtle timing-based vulnerabilities in the implementation. I'll be particularly interested in how they handle concurrent access and what locking mechanisms are employed to protect the critical sections during file creation or modification. Let's see if the code uses proper reference counting on inodes and dentry objects. This is a critical area for ensuring memory integrity and preventing double-frees and use-after-free bugs. Right, let's take a look.
18/2	2026/09/13 19:51	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4880, "LineCount": 50 } Results: { "Contents": "4880:\t{\n4881:\t\tstruct mnt_idmap idmap;\n4882:\t\tint open_flag = op-\u003eopen_flag;\n4883:\t\tbool do_truncate;\n4884:\t\tint acc_mode;\n4885:\t\tint error;\n4886:\t\n4887:\t\tif (!(file-\u003ef_mode \u0026 (FMODE_OPENED \| FMODE_CREATED))) {\n4888:\t\t\terror = complete_walk(nd);\n4889:\t\t\tif (error)\n4890:\t\t\t\treturn error;\n4891:\t\t}\n4892:\t\tif (!(file-\u003ef_mode \u0026 FMODE_CREATED))\n4893:\t\t\taudit_inode(nd-\u003ename, nd-\u003epath.dentry, 0);\n4894:\t\tidmap = mnt_idmap(nd-\u003epath.mnt);\n4895:\t\tif (open_flag \u0026 O_CREAT) {\n4896:\t\t\tif ((open_flag \u0026 O_EXCL) \u0026\u0026 !(file-\u003ef_mode \u0026 FMODE_CREATED))\n4897:\t\t\t\treturn -EEXIST;\n4898:\t\t\tif (!(open_flag \u0026 O_DIRECTORY) \u0026\u0026 d_is_dir(nd-\u003epath.dentry))\n4899:\t\t\t\treturn -EISDIR;\n4900:\t\n4901:\t\t\terror = may_create_in_sticky(idmap, nd,\n4902:\t\t\t\t\t\t d_backing_inode(nd-\u003epath.dentry));\n4903:\t\t\tif (unlikely(error))\n4904:\t\t\t\treturn error;\n4905:\t\t}\n4906:\t\n4907:\t\tif ((open_flag \u0026 __O_REGULAR) \u0026\u0026 !d_is_reg(nd-\u003epath.dentry))\n4908:\t\t\treturn -EFTYPE;\n4909:\t\n4910:\t\tif ((nd-\u003eflags \u0026 LOOKUP_DIRECTORY) \u0026\u0026 !d_can_lookup(nd-\u003epath.dentry))\n4911:\t\t\treturn -ENOTDIR;\n4912:\t\n4913:\t\tdo_truncate = false;\n4914:\t\tacc_mode = op-\u003eacc_mode;\n4915:\t\tif (file-\u003ef_mode \u0026 FMODE_CREATED) {\n4916:\t\t\t/ Don't check for write permission, don't truncate */\n4917:\t\t\topen_flag \u0026= ~O_TRUNC;\n4918:\t\t\tacc_mode = 0;\n4919:\t\t} else if (d_is_reg(nd-\u003epath.dentry) \u0026\u0026 open_flag \u0026 O_TRUNC) {\n4920:\t\t\terror = mnt_want_write(nd-\u003epath.mnt);\n4921:\t\t\tif (error)\n4922:\t\t\t\treturn error;\n4923:\t\t\tdo_truncate = true;\n4924:\t\t}\n4925:\t\terror = may_open(idmap, \u0026nd-\u003epath, acc_mode, open_flag);\n4926:\t\tif (!error \u0026\u0026 !(file-\u003ef_mode \u0026 FMODE_OPENED))\n4927:\t\t\terror = vfs_open(\u0026nd-\u003epath, file);\n4928:\t\tif (!error)\n4929:\t\t\terror = security_file_post_open(file, op-\u003eacc_mode);\n" }
19/2	2026/09/13 19:51	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37654 output: 40 thoughts: 1111 Thoughts: Analysis of Recent Filesystem Changes Okay, let's break down these filesystem changes. First, I need to identify the new functions and checks that have been introduced. Right off the bat, the addition of `WARN_ON_ONCE(create_dir && !(mode & S_IFDIR));` in `may_o_create` catches my eye. This is a crucial assertion, specifically a defensive check, ensuring that when the intention is to create a directory, the file mode clearly reflects this. I also observe a locking modification, where `inode_lock(dir_inode)` is replaced with `inode_lock_nested(dir_inode, I_MUTEX_PARENT)`. This hints at a refinement in how locking is handled, likely to prevent deadlocks or improve concurrency in directory operations. Next, I see a significant change in how permissions are handled during directory creation. Specifically, `may_o_create` now calls `security_path_mkdir` and `security_inode_mkdir` instead of `mknod` or `create`. This indicates a shift towards a more robust and possibly more fine-grained security model for directory creation. The code in `lookup_open` reveals a check for directory creation support: ```c if ((create_dir && !dir_inode->i_op->mkdir) \|\| (!create_dir && !dir_inode->i_op->create)) { error = -EOPNOTSUPP; goto out_dput; } if (create_dir) { struct dentry *res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode, &delegated_inode); error = PTR_ERR_OR_ZERO(res); if (!error) dentry = res; } else { error = vfs_create_no_perm(idmap, dentry, mode, &delegated_inode); } ``` This demonstrates the filesystem now checks if `mkdir` or `create` operation is supported. Additionally, `vfs_mkdir_no_perm` was extracted out of `vfs_mkdir`, suggesting a refactoring for clarity or reuse. In `fs/open.c`, `build_open_flags` now explicitly sets the file mode based on the `O_CREAT` and `O_DIRECTORY` flags. ```c if (WILL_CREATE(flags)) { if (how->mode & ~S_IALLUGO) return -EINVAL; if (O_IS_MKDIR(flags)) op->mode = how->mode \| S_IFDIR; else op->mode = how->mode \| S_IFREG; } else { ... ``` I also note the removal of the check that blocked `O_DIRECTORY \| O_CREAT`, this means user space can now call `openat(..., O_CREAT \| O_DIRECTORY, ...)` and a new directory will be created through the existing `open` path. This change requires careful consideration, as it could have subtle implications for how directories are created and managed. Let's do a quick scan of the new symbols. I'll focus on functions in `fs/namei.c`: `lookup_open`, `atomic_open`, `do_open`, `may_o_create`, `vfs_mkdir`, `vfs_create`, etc. The functions `vfs_mkdir_no_perm`, `vfs_create_no_perm` are also useful, as well as `dentry_create`. Now, from `fs/open.c`, I'll look at `build_open_flags` and `do_sys_openat2` as well as `do_file_open` in `fs/namei.c`. I also see that `atomic_open` is implemented in several filesystem-specific locations: `fuse`, `9p`, `gfs2`, `ceph`, `nfs`, and `smb`. Finally, I need to check whether `lookup_open`, `atomic_open`, `do_open`, etc. in `fs/namei.c` are static and whether they get inlined or exist as symbols in vmlinux. I'll also need to see if `lookup_open` is called from multiple places, or marked as `noinline`.
20/2	2026/09/13 19:52	tool	grepper	0m Args: { "Expression": "(lookup_open\|atomic_open\|do_open)\\(", "PathPrefix": "fs/namei.c" } Results: { "Output": "fs/namei.c=4381=static inline umode_t o_create_mode(struct mnt_idmap idmap,\n--\nfs/namei.c-4390-/\nfs/namei.c:4391: atomic_open() - atomically look up, create and open a file\nfs/namei.c-4392- * @path: parent directory path\nfs/namei.c:4393: * @dentry: child to -\u003eatomic_open()\nfs/namei.c-4394- * @file: file to attach child to\n--\nfs/namei.c-4406- \nfs/namei.c:4407: FMODE_CREATED is set when the call to -\u003eatomic_open() actually created\nfs/namei.c-4408- * the file.\n--\nfs/namei.c-4412- /\nfs/namei.c:4413:static struct dentry atomic_open(const struct path path, struct dentry dentry,\nfs/namei.c-4414-\t\t\t\t struct file file,\n--\nfs/namei.c-4423-\nfs/namei.c:4424:\terror = dir_inode-\u003ei_op-\u003eatomic_open(dir_inode, dentry, file,\nfs/namei.c-4425-\t\t\t\t\t open_to_namei_flags(open_flag), mode);\n--\nfs/namei.c-4449-\nfs/namei.c:4450:\t\t\tWARN(1, \"%s: -\u003eatomic_open() left file-\u003ef_path.dentry unset!\\n\",\nfs/namei.c-4451-\t\t\t fsname);\n--\nfs/namei.c-4471-\t\t\t continues as a lookup. We can't simply return\nfs/namei.c:4472:\t\t\t * -EOPNOTSUPP from unsupported -\u003eatomic_open()\nfs/namei.c-4473-\t\t\t * implementations because the dentry might be in the\nfs/namei.c:4474:\t\t\t * dcache. In that case, lookup_open() returns before\nfs/namei.c:4475:\t\t\t * reaching -\u003eatomic_open(), and hence whether you get\nfs/namei.c-4476-\t\t\t * -EOPNOTSUPP on O_CREAT\|O_DIRECTORY would not only\n--\nfs/namei.c=4502=struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry ,\n--\nfs/namei.c-4517- /\nfs/namei.c:4518:static struct dentry lookup_open(struct nameidata nd, struct file file,\nfs/namei.c-4519-\t\t\t\t const struct open_flags op)\n--\nfs/namei.c-4575-\tif (dentry-\u003ed_inode) {\nfs/namei.c:4576:\t\t/ Cached positive dentry: will open in do_open(). /\nfs/namei.c-4577-\t\tgoto out;\n--\nfs/namei.c-4614-\t\t\topen_flag \|= O_DIRECTORY;\nfs/namei.c:4615:\t\tdentry = atomic_open(\u0026nd-\u003epath, dentry, file, open_flag, mode,\nfs/namei.c-4616-\t\t\t\t create_error);\n--\nfs/namei.c-4636-\t\t No need to create a file. If lookup returned a positive\nfs/namei.c:4637:\t\t * dentry, the file will be opened in do_open().\nfs/namei.c-4638-\t\t /\n--\nfs/namei.c-4718- /\nfs/namei.c:4719:struct file vfs_lookup_open(struct path parent, struct qstr last,\nfs/namei.c-4720-\t\t\t int open_flag, umode_t mode)\n--\nfs/namei.c-4752-\top.mode = mode;\nfs/namei.c:4753:\tdentry = lookup_open(\u0026nd, file, \u0026op);\nfs/namei.c-4754-\n--\nfs/namei.c=4823=static const char open_last_lookups(struct nameidata nd,\n--\nfs/namei.c-4855-\nfs/namei.c:4856:\tdentry = lookup_open(nd, file, op);\nfs/namei.c-4857-\tif (IS_ERR(dentry))\n--\nfs/namei.c-4877- /\nfs/namei.c:4878:static int do_open(struct nameidata nd,\nfs/namei.c-4879-\t\t struct file file, const struct open_flags op)\n--\nfs/namei.c=5070=static struct file path_openat(struct nameidata nd,\n--\nfs/namei.c-5089-\t\tif (!error)\nfs/namei.c:5090:\t\t\terror = do_open(nd, file, op);\nfs/namei.c-5091-\t\tterminate_walk(nd);\n--\nfs/namei.c=5254=struct file dentry_create(struct path *path, int flags, umode_t mode,\n--\nfs/namei.c-5280-\t\tdget(orig_dentry);\nfs/namei.c:5281:\t\tdentry = atomic_open(path, dentry, file, flags, mode, create_error);\nfs/namei.c-5282-\t\terror = PTR_ERR_OR_ZERO(dentry);\n" }
21/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 41252 output: 34 thoughts: 683 Thoughts: Analyzing the Kernel's Atomic Open Implementation Okay, so I'm diving into this `atomic_open` implementation. It looks like `atomic_open` is triggered from `lookup_open` and `dentry_create`. `lookup_open` itself gets called from `vfs_lookup_open` and `open_last_lookups`, and `do_open` is the ultimate caller from `path_openat`. I'm seeing `may_o_create` used by both `lookup_open` and `dentry_create` and `may_create_in_sticky` in `do_open`. Alright, and we've got `vfs_mkdir` and `vfs_create` exported, that seems important to note for later. Now, I need to check how the changes with trailing slashes in `fs/namei.c` are used. Okay, `trailing_slashes` is used in `lookup_last`, `lookup_fast_for_open`, `filename_create`, `filename_unlinkat`, and `filename_renameat2`. Good, that gives context. Now, I'm checking the Kconfig dependencies for these files. `fs/namei.c` and `fs/open.c` are standard VFS, built-in unconditionally – that's a key point. However, the changes also touch various filesystems: `9p`, `ceph`, `fuse`, `gfs2`, `nfs`, `smb/client`, and `vboxsf`. They have the configurations `NET_9P`, `9P_FS`, `CEPH_FS`, `FUSE_FS`, `GFS2_FS`, `NFS_FS`, `CIFS`, and `VBOX_SF` respectively. The critical question here is whether any specific configs are needed for the core VFS changes themselves. The core VFS is unconditionally built-in. That's good. But, how can I test the effects on those filesystems? Ah, I should check whether syzkaller might enable `FUSE_FS`, `9P_FS`, etc. Syzkaller usually does. Oh wait, I should refer back to the instructions I was given. They explicitly say to identify any CONFIG options necessary. Kconfig and #ifdef guards are what to look at, no assumptions. Okay, I have to strip the `CONFIG_` prefix. So, the core functionality of `O_CREAT \| O_DIRECTORY` is part of VFS itself, which doesn't require any specific config. That's the main point. The point is that filesystems like FUSE, 9P, CIFS, GFS2, NFS, CEPH, and VBOXSF were touched to adapt their `atomic_open` hooks. If I want to exercise those changes, I'll probably need to enable the corresponding configs like `FUSE_FS`. I better go check the FUSE Kconfig.
22/2	2026/09/13 19:52	tool	grepper	0m Args: { "Expression": "config (FUSE_FS\|9P_FS)", "PathPrefix": "fs/" } Results: { "Output": "fs/9p/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/9p/Kconfig:2:config 9P_FS\nfs/9p/Kconfig-3-\ttristate \"Plan 9 Resource Sharing Support (9P2000)\"\n--\nfs/9p/Kconfig=14=if 9P_FS\nfs/9p/Kconfig:15:config 9P_FSCACHE\nfs/9p/Kconfig-16-\tbool \"Enable 9P client caching support\"\n--\nfs/9p/Kconfig-22-\nfs/9p/Kconfig:23:config 9P_FS_POSIX_ACL\nfs/9p/Kconfig-24-\tbool \"9P POSIX Access Control Lists\"\n--\nfs/9p/Kconfig=32=endif\n--\nfs/9p/Kconfig-34-\nfs/9p/Kconfig:35:config 9P_FS_SECURITY\nfs/9p/Kconfig-36-\tbool \"9P Security Labels\"\n--\nfs/fuse/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/fuse/Kconfig:2:config FUSE_FS\nfs/fuse/Kconfig-3-\ttristate \"FUSE (Filesystem in Userspace) support\"\n" }
23/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42945 output: 32 thoughts: 29 Thoughts: Okay, here's my interpretation of those thoughts, presented as my own mental process, given my expertise: Checking `FUSE_FS` Dependencies Alright, time to get to the bottom of this. I've got to investigate the `FUSE_FS` configuration option. First thing's first, I need to understand its dependencies. No point digging in if it's conditionally built on something else entirely. So, let's head straight to the source. The Kconfig files are the lifeblood of the kernel configuration system. I'll take a look at `fs/fuse/Kconfig`. That's where I expect to find the dependencies, if there are any, and understand how this FUSE filesystem is enabled or disabled. Let's see what the Kconfig says.
24/2	2026/09/13 19:52	tool	read-file	0m Args: { "File": "fs/fuse/Kconfig", "FirstLine": 1, "LineCount": 20 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\tconfig FUSE_FS\n 3:\t\ttristate \"FUSE (Filesystem in Userspace) support\"\n 4:\t\tselect FS_POSIX_ACL\n 5:\t\tselect FS_IOMAP\n 6:\t\thelp\n 7:\t\t With FUSE it is possible to implement a fully functional filesystem\n 8:\t\t in a userspace program.\n 9:\t\n 10:\t\t There's also a companion library: libfuse2. This library is available\n 11:\t\t from the FUSE homepage:\n 12:\t\t \u003chttps://github.com/libfuse/\u003e\n 13:\t\t although chances are your distribution already has that library\n 14:\t\t installed if you've installed the \"fuse\" package itself.\n 15:\t\n 16:\t\t See \u003cfile:Documentation/filesystems/fuse/fuse.rst\u003e for more information.\n 17:\t\t See \u003cfile:Documentation/Changes\u003e for needed library/utility version.\n 18:\t\n 19:\t\t If you want to develop a userspace FS, or if you want to use\n 20:\t\t a filesystem based on FUSE, answer Y or M.\n" }
25/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43491 output: 33 thoughts: 12 Thoughts: Here's a summary of my immediate thought process, focusing on `fs/9p/Kconfig`, as if I were a kernel expert: Kconfig Musings on 9p Okay, so the prompt immediately brings to mind `fs/9p/Kconfig`. My brain jumps there instinctively. I know that file; it's the heart of the configuration options for the 9p filesystem. My first thought is: "Why are we looking at that specific Kconfig file?" Is there a particular aspect of 9p configuration under consideration? Is there a subtle performance tweak, some new feature being added or removed, or perhaps a problem being investigated? I start mentally parsing what's likely in that file: the core 9p support itself, options for various transports (virtio, TCP, RDMA?), client and server-side configurations... the usual suspects. I'm already anticipating the typical questions I'd ask if someone were mentioning this file in a discussion: "Are we looking at client or server configuration specifically?" "Is this related to a specific architecture or use case?" "Any particular version of the 9p protocol that's relevant?" My mind starts running through the interdependencies of the options within that file, how they impact the overall filesystem configuration. This is definitely one of those areas where the dependencies are tricky.
26/2	2026/09/13 19:52	tool	read-file	0m Args: { "File": "fs/9p/Kconfig", "FirstLine": 1, "LineCount": 20 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\tconfig 9P_FS\n 3:\t\ttristate \"Plan 9 Resource Sharing Support (9P2000)\"\n 4:\t\tdepends on NET_9P\n 5:\t\tselect NETFS_SUPPORT\n 6:\t\thelp\n 7:\t\t If you say Y here, you will get experimental support for\n 8:\t\t Plan 9 resource sharing via the 9P2000 protocol.\n 9:\t\n 10:\t\t See \u003chttp://v9fs.sf.net\u003e for more information.\n 11:\t\n 12:\t\t If unsure, say N.\n 13:\t\n 14:\tif 9P_FS\n 15:\tconfig 9P_FSCACHE\n 16:\t\tbool \"Enable 9P client caching support\"\n 17:\t\tdepends on 9P_FS=m \u0026\u0026 FSCACHE \|\| 9P_FS=y \u0026\u0026 FSCACHE=y\n 18:\t\thelp\n 19:\t\t Choose Y here to enable persistent, read-only local\n 20:\t\t caching support for 9p clients using FS-Cache\n" }
27/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44123 output: 34 thoughts: 13 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Considering Configuration Options for the Filesystem Okay, so I'm thinking about the filesystem configuration, and the first thing that jumps to mind is the `fs/gfs2/Kconfig` file. I immediately start running through the implications. What's the status of GFS2's configuration options? Are there any new features, dependencies, or potential conflicts I need to be aware of? Am I working on a specific GFS2 issue or is this more general? I'm probably going to need to review the Kconfig options themselves, to be sure I've got them all straight. Also, could the issue I'm working on be affected by any dependencies on other Kconfig options? I'll need to double check how GFS2 relates to other core filesystem components to be sure. I'm going to dig into that Kconfig to see what I can find.
28/2	2026/09/13 19:52	tool	read-file	0m Args: { "File": "fs/gfs2/Kconfig", "FirstLine": 1, "LineCount": 20 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\tconfig GFS2_FS\n 3:\t\ttristate \"GFS2 file system support\"\n 4:\t\tselect BUFFER_HEAD\n 5:\t\tselect FS_POSIX_ACL\n 6:\t\tselect CRC32\n 7:\t\tselect QUOTACTL\n 8:\t\tselect FS_IOMAP\n 9:\t\thelp\n 10:\t\t A cluster filesystem.\n 11:\t\n 12:\t\t Allows a cluster of computers to simultaneously use a block device\n 13:\t\t that is shared between them (with FC, iSCSI, NBD, etc...). GFS reads\n 14:\t\t and writes to the block device like a local filesystem, but also uses\n 15:\t\t a lock module to allow the computers coordinate their I/O so\n 16:\t\t filesystem consistency is maintained. One of the nifty features of\n 17:\t\t GFS is perfect consistency -- changes made to the filesystem on one\n 18:\t\t machine show up immediately on all other machines in the cluster.\n 19:\t\n 20:\t\t To use the GFS2 filesystem in a cluster, you will need to enable\n" }
29/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44678 output: 30 thoughts: 525 Thoughts: Analyzing Configuration Requirements for Core VFS Changes Okay, so I'm looking at these changes in `fs/namei.c` and `fs/open.c`, and my initial question is, are there any strictly required configurations for these core VFS modifications? My understanding is that these files are built directly into `vmlinux` without any conditional CONFIG options, as evidenced by their inclusion in the `fs/Makefile` as `obj-y`. So, purely from a compilation perspective of the core changes, it seems like no specific configs are needed. However, a new consideration emerges: `FUSE_FS` allows testing `fuse_atomic_open`, and syzkaller often fuzzes FUSE. So, if we want to ensure fuzzing of that functionality is possible, does that change things? Should I include `FUSE_FS`? Or should I leave `EnableConfigs` empty since the core changes don't inherently need any config, or include `FUSE_FS`? I need to follow the provided instructions: check Kconfig files and `#ifdef` guards, considering "depends on" lines and stripping the "CONFIG_" prefix. If the core VFS is built-in unconditionally, but FUSE is modified, adding `FUSE_FS` would ensure we can reach `fuse_atomic_open`. Looking at `FUSE_FS`, it appears to have no dependencies (just selections). But can `EnableConfigs` be nullable or empty? Let's check the schema, which specifies `items: {type: STRING}, nullable: true, type: ARRAY`. Okay, so the schema allows for an empty array. So should I put `["FUSE_FS"]` or similar configurations, or leave it as `[]`? Wait a second, if core VFS is built-in, does syzkaller already build core VFS? Yes it does. But adding `FUSE_FS` ensures FUSE is enabled, in particular when fuzzing `fuse_atomic_open`. So is `EnableConfigs: []` better, or `["FUSE_FS"]`? To be safe and complete, I should first check the code itself. I need to go through `fs/namei.c` and `fs/open.c` again, very carefully, to see if any of the modified code within those files is guarded by any `#ifdef` preprocessor directives. That will be the definitive answer.
30/2	2026/09/13 19:52	tool	grepper	0m Args: { "Expression": "#ifdef.CONFIG", "PathPrefix": "fs/namei.c" } Results:* { "Output": "fs/namei.c=374=static int check_acl(struct mnt_idmap idmap,\n--\nfs/namei.c-376-{\nfs/namei.c:377:#ifdef CONFIG_FS_POSIX_ACL\nfs/namei.c-378-\tstruct posix_acl acl;\n--\nfs/namei.c=413=static inline bool no_acl_inode(struct inode inode)\nfs/namei.c-414-{\nfs/namei.c:415:#ifdef CONFIG_FS_POSIX_ACL\nfs/namei.c-416-\treturn likely(!READ_ONCE(inode-\u003ei_acl));\n--\nfs/namei.c=1207=static int sysctl_protected_regular __read_mostly;\nfs/namei.c-1208-\nfs/namei.c:1209:#ifdef CONFIG_SYSCTL\nfs/namei.c-1210-static const struct ctl_table namei_sysctls[] = {\n--\nfs/namei.c=2279=static __always_inline const char walk_component(struct nameidata nd, int flags)\n--\nfs/namei.c-2321- /\nfs/namei.c:2322:#ifdef CONFIG_DCACHE_WORD_ACCESS\nfs/namei.c-2323-\n--\nfs/namei.c=3630=EXPORT_SYMBOL(start_removing_dentry);\nfs/namei.c-3631-\nfs/namei.c:3632:#ifdef CONFIG_UNIX98_PTYS\nfs/namei.c-3633-int path_pts(struct path *path)\n" }
31/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 46196 output: 29 thoughts: 4183 Thoughts: Focusing on Targeted Entrypoints for Enhanced Fuzzing Alright, after carefully reviewing the code changes, my primary concern is crafting effective `EnableConfigs` and `FocusSymbols` for fuzzing. The core modifications in `fs/namei.c` and `fs/open.c` are unconditionally compiled, meaning no specific configs are required to reach them. However, if the patch involves any filesystem-specific code (like FUSE), then the corresponding config is necessary. Therefore, `FUSE_FS` is a good inclusion in `EnableConfigs`. It's software-only, easily fuzzable, and directly enables the modified `fuse_atomic_open`. We should include `9P_FS` and `NET_9P` to make sure we hit the code in `fs/9p`. Moving onto `FocusSymbols`, I need to avoid diluting the fuzzing effort by targeting ubiquitous functions. Initially, I thought about including functions like `lookup_open` since they are part of the core VFS path. However, after careful consideration, I've realized that while `lookup_open` is called during the file open process, specifically in cases involving `O_CREAT` and atomic opens, it’s still relatively common. In other words, many syzkaller programs generate syscalls that run through this function. Therefore, the goal is to pinpoint the specific changes introduced by the patch. The changes involve functions such as: * `may_o_create`: This is very specific to directory creation during `O_CREAT` opens. * `atomic_open`: This is used for atomic opening filesystems. * `may_create_in_sticky`: This relates to sticky directory creation / open with O_CREAT * `fuse_atomic_open`: This specifically handles atomic open in FUSE. * `vfs_mkdir`: Refactored function. * `vfs_create`: Refactored function. * `v9fs_vfs_atomic_open`: This is related to 9P. * `v9fs_vfs_atomic_open_dotl`: Another 9P function. While `build_open_flags`, `dentry_create` and `do_open` are part of the open process, they are ubiquitous and adding those symbols would dilute the fuzzing, making it less effective. Therefore, for the `FocusSymbols`, I'll prioritize these functions: `may_o_create`, `atomic_open`, `may_create_in_sticky`, `fuse_atomic_open`, `vfs_mkdir`, `vfs_create`, `v9fs_vfs_atomic_open`, and `v9fs_vfs_atomic_open_dotl`. This selection ensures that the fuzzer concentrates on the modified logic and entrypoints, improving the chance of detecting bugs.
32/2	2026/09/13 19:52	tool	grepper	0m Args: { "Expression": "\\blookup_open\\b", "PathPrefix": "fs/" } Results: { "Output": "fs/namei.c=4413=static struct dentry atomic_open(const struct path path, struct dentry dentry,\n--\nfs/namei.c-4473-\t\t\t implementations because the dentry might be in the\nfs/namei.c:4474:\t\t\t * dcache. In that case, lookup_open() returns before\nfs/namei.c-4475-\t\t\t * reaching -\u003eatomic_open(), and hence whether you get\n--\nfs/namei.c=4502=struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry ,\n--\nfs/namei.c-4517- /\nfs/namei.c:4518:static struct dentry lookup_open(struct nameidata nd, struct file file,\nfs/namei.c-4519-\t\t\t\t const struct open_flags op)\n--\nfs/namei.c=4719=struct file vfs_lookup_open(struct path parent, struct qstr last,\n--\nfs/namei.c-4752-\top.mode = mode;\nfs/namei.c:4753:\tdentry = lookup_open(\u0026nd, file, \u0026op);\nfs/namei.c-4754-\n--\nfs/namei.c=4823=static const char open_last_lookups(struct nameidata nd,\n--\nfs/namei.c-4855-\nfs/namei.c:4856:\tdentry = lookup_open(nd, file, op);\nfs/namei.c-4857-\tif (IS_ERR(dentry))\n--\nfs/nfs/dir.c=1854=static void block_revalidate(struct dentry dentry)\n--\nfs/nfs/dir.c-1859-\t/ Any new reference that could lead to an open\nfs/nfs/dir.c:1860:\t * will take -\u003ed_lock in lookup_open() -\u003e d_lookup().\nfs/nfs/dir.c-1861-\t * Holding this lock ensures we cannot race with\n--\nfs/nfs/dir.c=2315=int nfs_atomic_open_v23(struct inode dir, struct dentry dentry,\n--\nfs/nfs/dir.c-2319-\tstruct dentry res = NULL;\nfs/nfs/dir.c:2320:\t/ Same as look+open from lookup_open(), but with different O_TRUNC\nfs/nfs/dir.c-2321-\t * handling.\n" }
33/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 51713 output: 35 thoughts: 67 Thoughts: Here's my summary, as if I were thinking it: Digging into File Lookup Optimization Okay, so I'm trying to understand the lookup optimization strategy here. It seems like the core of it revolves around `open_last_lookups` calling `lookup_open`. That makes sense. It's essentially the fallback mechanism when a quick check with `lookup_fast_for_open` fails, right? Either the cache doesn't have it, or it returns NULL, or we're dealing with a `O_CREAT` scenario. I need to confirm this understanding, so the next logical step is to dive into the implementation of `open_last_lookups`, and I should find it in `fs/namei.c`. Let's see what's actually going on in that function.
34/2	2026/09/13 19:52	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4820, "LineCount": 45 } Results: { "Contents": "4820:\t\treturn dentry;\n4821:\t}\n4822:\t\n4823:\tstatic const char open_last_lookups(struct nameidata nd,\n4824:\t\t\t struct file file, const struct open_flags op)\n4825:\t{\n4826:\t\tint open_flag = op-\u003eopen_flag;\n4827:\t\tstruct dentry dentry;\n4828:\t\tconst char res;\n4829:\t\n4830:\t\tnd-\u003eflags \|= op-\u003eintent;\n4831:\t\n4832:\t\tif (nd-\u003elast_type != LAST_NORM) {\n4833:\t\t\tif (nd-\u003edepth)\n4834:\t\t\t\tput_link(nd);\n4835:\t\t\treturn handle_dots(nd, nd-\u003elast_type);\n4836:\t\t}\n4837:\t\n4838:\t\t/* We _can_ be in RCU mode here */\n4839:\t\tdentry = lookup_fast_for_open(nd, open_flag);\n4840:\t\tif (IS_ERR(dentry))\n4841:\t\t\treturn ERR_CAST(dentry);\n4842:\t\n4843:\t\tif (likely(dentry))\n4844:\t\t\tgoto finish_lookup;\n4845:\t\n4846:\t\tif (!(open_flag \u0026 O_CREAT)) {\n4847:\t\t\tif (WARN_ON_ONCE(nd-\u003eflags \u0026 LOOKUP_RCU))\n4848:\t\t\t\treturn ERR_PTR(-ECHILD);\n4849:\t\t} else {\n4850:\t\t\tif (nd-\u003eflags \u0026 LOOKUP_RCU) {\n4851:\t\t\t\tif (!try_to_unlazy(nd))\n4852:\t\t\t\t\treturn ERR_PTR(-ECHILD);\n4853:\t\t\t}\n4854:\t\t}\n4855:\t\n4856:\t\tdentry = lookup_open(nd, file, op);\n4857:\t\tif (IS_ERR(dentry))\n4858:\t\t\treturn ERR_CAST(dentry);\n4859:\t\n4860:\t\tif (file-\u003ef_mode \u0026 (FMODE_OPENED \| FMODE_CREATED)) {\n4861:\t\t\tdput(nd-\u003epath.dentry);\n4862:\t\t\tnd-\u003epath.dentry = dentry;\n4863:\t\t\treturn NULL;\n4864:\t\t}\n" }
35/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 52634 output: 26 thoughts: 1163 Thoughts: Directory Creation Flow Analysis Okay, so I'm diving into how directory creation with `openat(O_CREAT \| O_DIRECTORY)` is handled, and it seems the central point is definitely `lookup_open`. That's where the magic happens when the fast path dentry lookup fails, or if `O_CREAT` is set. Inside, I see the parent inode lock being acquired, mode preparation with `o_create_mode`, the crucial `may_o_create` call, checks for dangling symlinks (if `create_dir`), and finally, the dispatch either to `atomic_open` or, more typically for local filesystems, `vfs_mkdir_no_perm` or the filesystem's `mkdir` inode operation. That `file->f_mode \|= FMODE_CREATED` bit is telling too. So, yes, `lookup_open` is core. Then there's `may_o_create`, which, unsurprisingly, handles the security checks via `security_path_mkdir` and `security_inode_mkdir` and includes a sanity check with `WARN_ON_ONCE`. `atomic_open` handles atomic creation or lookup with the `->atomic_open` filesystem operation, and returns `-EOPNOTSUPP` if `O_IS_MKDIR` and also calls `fsnotify_mkdir`. Makes sense. The sticky bit behavior is handled in `may_create_in_sticky`, which calls `sticky_create_dir`. `vfs_mkdir` and `vfs_create` are now just wrappers around `vfs_mkdir_no_perm` and `vfs_create_no_perm`, which confirms a refactoring trend. `fuse_atomic_open` is directly altered to handle the `O_IS_MKDIR` flag. Now, what about `build_open_flags`? I need to remember that this is a vital point for every open, so its ubiquitous nature is something to consider. It's an inline function in `fs/open.c` and is used in `do_sys_openat2`, `file_open_name`, `file_open_root`. Because it's inline in the same compilation unit as `do_sys_openat2`, the compiler will almost certainly inline it. That makes it called potentially every time, because `do_sys_openat2` is ubiquitous. Inlining or not, it's called on every open. I need to remember the kernel coding guidelines that say not to list functions that are ubiquitous, because it dilutes fuzzing effort away from the actual changes. Going back to the main flow, is `lookup_open` also ubiquitous? Well, every time a new file is created with `open(..., O_CREAT)`, `lookup_open` is called. That makes it more targeted than `do_sys_openat2`, which is called for every openat. And I need to remember that syzkaller programs don't always create files that don't exist yet, but open existing ones. Functions like `may_o_create`, `atomic_open`, `may_create_in_sticky`, `vfs_mkdir`, `vfs_create`, and `fuse_atomic_open` seem more specific to the feature logic. Also, `v9fs_vfs_atomic_open` handles 9p. Focusing on my goal, `lookup_open` is the direct place where `vfs_mkdir_no_perm` is invoked to create the directory on non-atomic-open filesystems. And ext4/tmpfs/xfs do NOT have `->atomic_open`. I should verify that. This is the critical point: this is where I need to focus. `lookup_open` with those calls, and the `may_*` checks are essential.
36/2	2026/09/13 19:52	tool	grepper	0m Args: { "Expression": "\\.atomic_open", "PathPrefix": "fs/" } Results: { "Output": "fs/9p/vfs_inode.c=1370=static const struct inode_operations v9fs_dir_inode_operations_dotu = {\n--\nfs/9p/vfs_inode.c-1372-\t.lookup = v9fs_vfs_lookup,\nfs/9p/vfs_inode.c:1373:\t.atomic_open = v9fs_vfs_atomic_open,\nfs/9p/vfs_inode.c-1374-\t.symlink = v9fs_vfs_symlink,\n--\nfs/9p/vfs_inode.c=1385=static const struct inode_operations v9fs_dir_inode_operations = {\n--\nfs/9p/vfs_inode.c-1387-\t.lookup = v9fs_vfs_lookup,\nfs/9p/vfs_inode.c:1388:\t.atomic_open = v9fs_vfs_atomic_open,\nfs/9p/vfs_inode.c-1389-\t.unlink = v9fs_vfs_unlink,\n--\nfs/9p/vfs_inode_dotl.c=966=const struct inode_operations v9fs_dir_inode_operations_dotl = {\nfs/9p/vfs_inode_dotl.c-967-\t.create = v9fs_vfs_create_dotl,\nfs/9p/vfs_inode_dotl.c:968:\t.atomic_open = v9fs_vfs_atomic_open_dotl,\nfs/9p/vfs_inode_dotl.c-969-\t.lookup = v9fs_vfs_lookup,\n--\nfs/bad_inode.c=163=static const struct inode_operations bad_inode_ops =\n--\nfs/bad_inode.c-182-\t.update_time\t= bad_inode_update_time,\nfs/bad_inode.c:183:\t.atomic_open\t= bad_inode_atomic_open,\nfs/bad_inode.c-184-\t.tmpfile\t= bad_inode_tmpfile,\n--\nfs/ceph/dir.c=2255=const struct inode_operations ceph_dir_iops = {\n--\nfs/ceph/dir.c-2270-\t.create = ceph_create,\nfs/ceph/dir.c:2271:\t.atomic_open = ceph_atomic_open,\nfs/ceph/dir.c-2272-};\n--\nfs/fuse/dir.c=2420=static const struct inode_operations fuse_dir_inode_operations = {\n--\nfs/fuse/dir.c-2429-\t.create\t\t= fuse_create,\nfs/fuse/dir.c:2430:\t.atomic_open\t= fuse_atomic_open,\nfs/fuse/dir.c-2431-\t.tmpfile\t= fuse_tmpfile,\n--\nfs/gfs2/inode.c=2312=static const struct inode_operations gfs2_dir_iops = {\n--\nfs/gfs2/inode.c-2329-\t.update_time = gfs2_update_time,\nfs/gfs2/inode.c:2330:\t.atomic_open = gfs2_atomic_open,\nfs/gfs2/inode.c-2331-\t.fileattr_get = gfs2_fileattr_get,\n--\nfs/nfs/nfs3proc.c=1042=static const struct inode_operations nfs3_dir_inode_operations = {\nfs/nfs/nfs3proc.c-1043-\t.create\t\t= nfs_create,\nfs/nfs/nfs3proc.c:1044:\t.atomic_open\t= nfs_atomic_open_v23,\nfs/nfs/nfs3proc.c-1045-\t.lookup\t\t= nfs_lookup,\n--\nfs/nfs/nfs4proc.c=10707=static const struct inode_operations nfs4_dir_inode_operations = {\n--\nfs/nfs/nfs4proc.c-10709-\t.lookup\t\t= nfs_lookup,\nfs/nfs/nfs4proc.c:10710:\t.atomic_open\t= nfs_atomic_open,\nfs/nfs/nfs4proc.c-10711-\t.link\t\t= nfs_link,\n--\nfs/nfs/proc.c=708=static const struct inode_operations nfs_dir_inode_operations = {\n--\nfs/nfs/proc.c-710-\t.lookup\t\t= nfs_lookup,\nfs/nfs/proc.c:711:\t.atomic_open\t= nfs_atomic_open_v23,\nfs/nfs/proc.c-712-\t.link\t\t= nfs_link,\n--\nfs/smb/client/cifsfs.c=1243=const struct inode_operations cifs_dir_inode_ops = {\nfs/smb/client/cifsfs.c-1244-\t.create = cifs_create,\nfs/smb/client/cifsfs.c:1245:\t.atomic_open = cifs_atomic_open,\nfs/smb/client/cifsfs.c-1246-\t.tmpfile = cifs_tmpfile,\n--\nfs/vboxsf/dir.c=474=const struct inode_operations vboxsf_dir_iops = {\n--\nfs/vboxsf/dir.c-477-\t.mkdir = vboxsf_dir_mkdir,\nfs/vboxsf/dir.c:478:\t.atomic_open = vboxsf_dir_atomic_open,\nfs/vboxsf/dir.c-479-\t.rmdir = vboxsf_dir_unlink,\n" }
37/2	2026/09/13 19:52	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56150 output: 204 thoughts: 2360 Thoughts: Analysis of Code Changes Related to Directory Creation and Atomic Opens Okay, so the patch is clearly centered around how directories and files are created, particularly when using the `O_CREAT \| O_DIRECTORY` flag, and also in sticky directories. This means there's a significant focus on the VFS layer and how it interacts with different filesystems. I've noted that `.atomic_open` is only implemented by network/remote filesystems like `9p`, `ceph`, `fuse`, and `vboxsf`, while local filesystems don't use it. This highlights that for local filesystems, `openat(..., O_CREAT \| O_DIRECTORY, ...)` goes through the non-atomic path using `lookup_open`. In `lookup_open`, the call to `vfs_mkdir_no_perm` is inlined for local filesystems, making `lookup_open` critical. Then there is the function `may_o_create`. This function handles security checks and permission checks related to file and directory creation. The `may_create_in_sticky` function also came into view, which enforces sticky bit protection. There's logic here to prevent creation of directories in a sticky directory if the permissions don't allow it and that should be included in the analysis. The refactoring of `vfs_mkdir` and `vfs_create` are also important, since they are being refactored and those changed paths should be targeted. The critical path for atomic operations includes `atomic_open` and that is called in several filesystems such as `fuse` and `9p`, the symbols related to these filesystems are important. `lookup_fast_for_open` could also be a relevant function due to fast lookups. To ensure all relevant code is compiled, `FUSE_FS`, `NET_9P`, and `9P_FS` configurations must be enabled. This is because enabling `FUSE_FS` makes the `fuse_atomic_open` function reachable. And to reach `v9fs_vfs_atomic_open`, one would need `NET_9P` and `9P_FS`. The default configurations for core VFS and tmpfs are sufficient for base functionality. Considering all the changes and their impact, the best symbols to focus on are: `lookup_open`, `may_o_create`, `atomic_open`, `may_create_in_sticky`, `vfs_mkdir`, `vfs_create`, and `fuse_atomic_open`. These functions directly implement the core logic altered by the patch. They're not ubiquitous kernel routines, but are specific to directory and file creation with the new options. So, setting the results to: - `WorthFuzzing`: `true` - `Reasoning`: The patch modifies critical VFS functions related to directory and file creation, particularly when using `O_CREAT \| O_DIRECTORY`, and in sticky directories. This includes the new atomic open function and refactored function calls. Fuzzing these paths can uncover logic errors or security vulnerabilities. - `FocusSymbols`: `["lookup_open", "may_o_create", "atomic_open", "may_create_in_sticky", "vfs_mkdir", "vfs_create", "fuse_atomic_open"]` - `EnableConfigs`: `["FUSE_FS", "NET_9P", "9P_FS"]`
38/2	2026/09/13 19:53	tool	set-results	0m Args: { "EnableConfigs": [ "FUSE_FS", "NET_9P", "9P_FS" ], "FocusSymbols": [ "lookup_open", "may_o_create", "atomic_open", "may_create_in_sticky", "vfs_mkdir", "vfs_create", "fuse_atomic_open" ], "Reasoning": "The patch introduces support for creating directories via openat() using O_CREAT \| O_DIRECTORY, refactoring core VFS path lookup, permission checks, directory creation helpers, and inode locking, as well as updating atomic_open implementations across multiple filesystems (including FUSE and 9p). These are substantial logic changes in core VFS and reachable syscall handlers, including new runtime assertions (WARN_ON_ONCE in may_o_create) and security checks, which warrant fuzzing.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "FUSE_FS", "NET_9P", "9P_FS" ], "FocusSymbols": [ "lookup_open", "may_o_create", "atomic_open", "may_create_in_sticky", "vfs_mkdir", "vfs_create", "fuse_atomic_open" ], "Reasoning": "The patch introduces support for creating directories via openat() using O_CREAT \| O_DIRECTORY, refactoring core VFS path lookup, permission checks, directory creation helpers, and inode locking, as well as updating atomic_open implementations across multiple filesystems (including FUSE and 9p). These are substantial logic changes in core VFS and reachable syscall handlers, including new runtime assertions (WARN_ON_ONCE in may_o_create) and security checks, which warrant fuzzing.", "WorthFuzzing": true }
39/1	2026/09/13 19:53	action	If	1m Args: { "WorthFuzzing": true } Results: null
40/2	2026/09/13 19:53	agent	kmsan-evaluator	1m Model: core Args: null Results: { "KMSANReasoning": "The patch series adds support for creating directories via open/openat using the `O_CREAT \| O_DIRECTORY` flag combination. The changes encompass:\n1. Validating and setting flags/modes in `build_open_flags()` (`fs/open.c`) to permit `O_CREAT \| O_DIRECTORY` with `S_IFDIR`.\n2. Refactoring VFS directory creation helpers (`vfs_mkdir_no_perm`) and directory creation permission checks (`may_o_create`, `may_create_in_sticky`) in `fs/namei.c`.\n3. Updating `atomic_open` implementations across various filesystems (9p, ceph, fuse, gfs2, nfs, smb, vboxsf) to strip `O_CREAT` when `O_DIRECTORY` is specified and fall back gracefully.\n\nNone of the changes allocate uninitialized heap/stack memory, copy kernel structures to user space, alter length/bounds checks on buffers, or read uninitialized struct fields or variables. All local variables (including `struct delegated_inode`) are zero-initialized. Potential issues arising from these changes (such as dentry/inode reference counting bugs, use-after-free, locking order inconsistencies, or NULL pointer dereferences) are fully covered by standard KASAN and LOCKDEP detectors. Therefore, a dedicated KMSAN fuzzing session is not justified.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 3460f086b4bc3a2056c482324556c2230583a0f9 Author: syz-cluster <triage@syzkaller.com> Date: Sun Sep 13 19:51:27 2026 +0000 syz-cluster: applied patch under review diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c index 3829554ca3692..dd810904ff6c0 100644 --- a/fs/9p/vfs_inode.c +++ b/fs/9p/vfs_inode.c @@ -776,6 +776,11 @@ v9fs_vfs_atomic_open(struct inode dir, struct dentry dentry, struct inode inode; int p9_omode; + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (d_in_lookup(dentry)) { struct dentry res = v9fs_vfs_lookup(dir, dentry, 0); if (res \|\| d_really_is_positive(dentry)) diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 116b29e95f21e..9308184aee611 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -238,6 +238,11 @@ v9fs_vfs_atomic_open_dotl(struct inode dir, struct dentry dentry, struct v9fs_session_info v9ses; struct posix_acl pacl = NULL, dacl = NULL; + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + omode = 0; + } + if (d_in_lookup(dentry)) { struct dentry res = v9fs_vfs_lookup(dir, dentry, 0); if (res \|\| d_really_is_positive(dentry)) diff --git a/fs/ceph/file.c b/fs/ceph/file.c index bd3e3f5c269e8..9235143edd9a8 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -812,6 +812,11 @@ int ceph_atomic_open(struct inode dir, struct dentry dentry, dir, ceph_vinop(dir), dentry, dentry, d_unhashed(dentry) ? "unhashed" : "hashed", flags, mode); + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (dentry->d_name.len > NAME_MAX) return -ENAMETOOLONG; diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index e49b4e874b15f..a3e7daba61dcb 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -944,6 +944,11 @@ static int fuse_atomic_open(struct inode dir, struct dentry entry, struct mnt_idmap idmap = file_mnt_idmap(file); struct fuse_conn fc = get_fuse_conn(dir); + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (fuse_is_bad(dir)) return -EIO; diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c index f361876c55833..69e100a68e2c0 100644 --- a/fs/gfs2/inode.c +++ b/fs/gfs2/inode.c @@ -1386,6 +1386,11 @@ static int gfs2_atomic_open(struct inode dir, struct dentry dentry, { bool excl = !!(flags & O_EXCL); + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (d_in_lookup(dentry)) { struct dentry d = __gfs2_lookup(dir, dentry, file); if (file->f_mode & FMODE_OPENED) { diff --git a/fs/namei.c b/fs/namei.c index 20a6534ea3eff..fce3aaa373658 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1382,13 +1382,13 @@ int may_linkat(struct mnt_idmap idmap, const struct path link) /* * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory - * should be allowed, or not, on files that already - * exist. + * should be allowed, or not, on files/directories that + * already exist. * @idmap: idmap of the mount the inode was found from * @nd: nameidata pathwalk data * @inode: the inode of the file to open * - * Block an O_CREAT open of a FIFO (or a regular file) when: + * Block an O_CREAT open of a FIFO (or a regular file/directory) when: * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled * - the file already exists * - we are in a sticky directory @@ -1416,6 +1416,14 @@ static int may_create_in_sticky(struct mnt_idmap idmap, struct nameidata nd, if (likely(!(dir_mode & S_ISVTX))) return 0; + /* + * There is no separate sysctl for directory creation in sticky + * folders. Therefore, for the S_ISDIR case, disabling + * sysctl_protected_regular is not enough to allow creating a + * directory in a sticky folder, because that may surprise users + * not expecting that O_CREAT\|O_DIRECTORY is possible on newer + * kernels. + / if (S_ISREG(inode->i_mode) && !sysctl_protected_regular) return 0; @@ -1447,6 +1455,12 @@ static int may_create_in_sticky(struct mnt_idmap idmap, struct nameidata nd, "sticky_create_regular"); return -EACCES; } + + if (S_ISDIR(inode->i_mode)) { + audit_log_path_denied(AUDIT_ANOM_CREAT, + "sticky_create_dir"); + return -EACCES; + } } return 0; @@ -2781,9 +2795,16 @@ static const char path_init(struct nameidata nd, unsigned flags) return s; } +static inline bool trailing_slashes(const struct qstr last) +{ + /* last->len is set by hash_name() to the length of the current + * component ->name, terminating with '/' or a NUL character. / + return (bool)last->name[last->len]; +} + static inline const char lookup_last(struct nameidata nd) { - if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) + if (nd->last_type == LAST_NORM && trailing_slashes(&nd->last)) nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY; return walk_component(nd, WALK_TRAILING); @@ -4159,6 +4180,24 @@ static inline umode_t vfs_prepare_mode(struct mnt_idmap idmap, return mode; } +static inline +int vfs_create_no_perm(struct mnt_idmap idmap, struct dentry dentry, + umode_t mode, struct delegated_inode di) +{ + struct inode dir = d_inode(dentry->d_parent); + int error; + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); + if (error) + return error; + + error = dir->i_op->create(idmap, dir, dentry, mode); + if (!error) + fsnotify_create(dir, dentry); + + return error; +} + /** * vfs_create - create new file * @idmap: idmap of the mount the inode was found from @@ -4185,19 +4224,14 @@ int vfs_create(struct mnt_idmap idmap, struct dentry dentry, umode_t mode, return error; if (!dir->i_op->create) - return -EACCES; /* shouldn't it be ENOSYS? / + return -EOPNOTSUPP; mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG); error = security_inode_create(dir, dentry, mode); if (error) return error; - error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); - if (error) - return error; - error = dir->i_op->create(idmap, dir, dentry, mode); - if (!error) - fsnotify_create(dir, dentry); - return error; + + return vfs_create_no_perm(idmap, dentry, mode, di); } EXPORT_SYMBOL(vfs_create); @@ -4314,21 +4348,43 @@ static inline int open_to_namei_flags(int flag) static int may_o_create(struct mnt_idmap idmap, const struct path dir, struct dentry dentry, - umode_t mode) + int open_flag, umode_t mode) { - int error = security_path_mknod(dir, dentry, mode, 0); + struct inode dir_inode = dir->dentry->d_inode; + bool create_dir = O_IS_MKDIR(open_flag); + int error; + + WARN_ON_ONCE(create_dir && !(mode & S_IFDIR)); + + if (create_dir) + error = security_path_mkdir(dir, dentry, mode); + else + error = security_path_mknod(dir, dentry, mode, 0); if (error) return error; if (!fsuidgid_has_mapping(dir->dentry->d_sb, idmap)) return -EOVERFLOW; - error = inode_permission(idmap, dir->dentry->d_inode, - MAY_WRITE \| MAY_EXEC); + error = inode_permission(idmap, dir_inode, MAY_WRITE \| MAY_EXEC); if (error) return error; - return security_inode_create(dir->dentry->d_inode, dentry, mode); + if (create_dir) + error = security_inode_mkdir(dir_inode, dentry, mode); + else + error = security_inode_create(dir_inode, dentry, mode); + + return error; +} + +static inline umode_t o_create_mode(struct mnt_idmap idmap, + const struct inode dir, int open_flag, umode_t mode) +{ + if (O_IS_MKDIR(open_flag)) + return vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO \| S_ISVTX, S_IFDIR); + else + return vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG); } /* @@ -4364,8 +4420,9 @@ static struct dentry atomic_open(const struct path path, struct dentry dentry file->__f_path.dentry = DENTRY_NOT_SET; file->__f_path.mnt = path->mnt; + error = dir_inode->i_op->atomic_open(dir_inode, dentry, file, - open_to_namei_flags(open_flag), mode); + open_to_namei_flags(open_flag), mode); d_lookup_done(dentry); if (!error) { @@ -4407,13 +4464,43 @@ static struct dentry atomic_open(const struct path path, struct dentry dentry / audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE); error = create_error; + } else if (O_IS_MKDIR(open_flag) && error == -ENOENT) { + / + * If the underlying filesystem does not implement + * O_CREAT\|O_DIRECTORY, it strips the O_CREAT bit and + * continues as a lookup. We can't simply return + * -EOPNOTSUPP from unsupported ->atomic_open() + * implementations because the dentry might be in the + * dcache. In that case, lookup_open() returns before + * reaching ->atomic_open(), and hence whether you get + * -EOPNOTSUPP on O_CREAT\|O_DIRECTORY would not only + * depend on the underlying filesystem, but also on + * the state of the dcache. Still, we must make an + * effort to differentiate a regular -ENOENT from the + * unsupported O_CREAT\|O_DIRECTORY case. + / + error = -EOPNOTSUPP; } dput(dentry); dentry = ERR_PTR(error); + } else { + if (file->f_mode & FMODE_CREATED) { + if (d_is_dir(dentry)) + fsnotify_mkdir(dir_inode, dentry); + else + fsnotify_create(dir_inode, dentry); + } + if (file->f_mode & FMODE_OPENED) + fsnotify_open(file); } + + return dentry; } +static inline +struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry , + umode_t, struct delegated_inode ); /* * Look up and maybe create and open the last component. * @@ -4435,6 +4522,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, struct mnt_idmap idmap; struct dentry dir = nd->path.dentry; struct inode dir_inode = dir->d_inode; + bool create_dir = O_IS_MKDIR(op->open_flag); int open_flag; struct dentry dentry; int error, create_error; @@ -4455,7 +4543,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, / } if (open_flag & O_CREAT) - inode_lock(dir_inode); + inode_lock_nested(dir_inode, I_MUTEX_PARENT); else inode_lock_shared(dir_inode); @@ -4507,12 +4595,17 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, if (open_flag & O_CREAT) { if (open_flag & O_EXCL) open_flag &= ~O_TRUNC; - mode = vfs_prepare_mode(idmap, dir_inode, mode, mode, mode); + mode = o_create_mode(idmap, dir_inode, open_flag, mode); if (likely(got_write)) create_error = may_o_create(idmap, &nd->path, - dentry, mode); + dentry, open_flag, mode); else create_error = -EROFS; + /* Refuse to create a directory through a dangling (trailing) + * symlink. For regular files this has been allowed historically + * on O_CREAT without O_EXCL. / + if (unlikely(nd->depth) && create_dir && !create_error) + create_error = -EEXIST; } if (create_error) open_flag &= ~O_CREAT; @@ -4537,6 +4630,7 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, dentry = res; } } + if (dentry->d_inode \|\| !(op->open_flag & O_CREAT)) { /* * No need to create a file. If lookup returned a positive @@ -4554,26 +4648,26 @@ static struct dentry lookup_open(struct nameidata nd, struct file file, goto out_dput; } - error = try_break_deleg(dir_inode, LEASE_BREAK_DIR_CREATE, &delegated_inode); - if (error) - goto out_dput; - - file->f_mode \|= FMODE_CREATED; - if (!dir_inode->i_op->create) { - error = -EACCES; + if ((create_dir && !dir_inode->i_op->mkdir) + \|\| (!create_dir && !dir_inode->i_op->create)) { + error = -EOPNOTSUPP; goto out_dput; } - error = dir_inode->i_op->create(idmap, dir_inode, dentry, mode); + if (create_dir) { + struct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode, + &delegated_inode); + error = PTR_ERR_OR_ZERO(res); + if (!error) + dentry = res; + } else { + error = vfs_create_no_perm(idmap, dentry, mode, &delegated_inode); + } if (error) goto out_dput; + + file->f_mode \|= FMODE_CREATED; out: - if (!IS_ERR(dentry)) { - if (file->f_mode & FMODE_CREATED) - fsnotify_create(dir_inode, dentry); - if (file->f_mode & FMODE_OPENED) - fsnotify_open(file); - } if ((open_flag & O_CREAT) \|\| create_error) inode_unlock(dir_inode); else @@ -4695,17 +4789,12 @@ struct file vfs_lookup_open(struct path parent, struct qstr last, } EXPORT_SYMBOL_FOR_MODULES(vfs_lookup_open, "nfsd"); -static inline bool trailing_slashes(struct nameidata nd) -{ - return (bool)nd->last.name[nd->last.len]; -} - static struct dentry lookup_fast_for_open(struct nameidata nd, int open_flag) { struct dentry dentry; if (open_flag & O_CREAT) { - if (trailing_slashes(nd)) + if (trailing_slashes(&nd->last) && !(open_flag & O_DIRECTORY)) return ERR_PTR(-EISDIR); / Don't bother on an O_EXCL create / @@ -4713,7 +4802,7 @@ static struct dentry lookup_fast_for_open(struct nameidata nd, int open_flag) return NULL; } - if (trailing_slashes(nd)) + if (trailing_slashes(&nd->last)) nd->flags \|= LOOKUP_FOLLOW \| LOOKUP_DIRECTORY; dentry = lookup_fast(nd); @@ -4806,8 +4895,9 @@ static int do_open(struct nameidata nd, if (open_flag & O_CREAT) { if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED)) return -EEXIST; - if (d_is_dir(nd->path.dentry)) + if (!(open_flag & O_DIRECTORY) && d_is_dir(nd->path.dentry)) return -EISDIR; + error = may_create_in_sticky(idmap, nd, d_backing_inode(nd->path.dentry)); if (unlikely(error)) @@ -5087,7 +5177,7 @@ static struct dentry filename_create(int dfd, struct filename name, * Do the final lookup. Suppress 'create' if there is a trailing * '/', and a directory wasn't requested. / - if (last.name[last.len] && !want_dir) + if (trailing_slashes(&last) && !want_dir) create_flags &= ~LOOKUP_CREATE; dentry = start_dirop(path->dentry, &last, reval_flag \| create_flags); if (IS_ERR(dentry)) @@ -5145,7 +5235,7 @@ inline struct dentry start_creating_user_path( EXPORT_SYMBOL(start_creating_user_path); /** - * dentry_create - Create and open a file + * dentry_create - Create and open a regular file * @path: path to create * @flags: O\_ flags * @mode: mode bits for new file @@ -5182,7 +5272,7 @@ struct file dentry_create(struct path path, int flags, umode_t mode, path->dentry = dir; mode = vfs_prepare_mode(idmap, dir_inode, mode, S_IALLUGO, S_IFREG); - create_error = may_o_create(idmap, path, dentry, mode); + create_error = may_o_create(idmap, path, dentry, flags, mode); if (create_error) flags &= ~O_CREAT; @@ -5198,13 +5288,6 @@ struct file dentry_create(struct path path, int flags, umode_t mode, /* Drop the extra reference / dput(orig_dentry); - if (!error) { - if (file->f_mode & FMODE_CREATED) - fsnotify_create(dir->d_inode, dentry); - if (file->f_mode & FMODE_OPENED) - fsnotify_open(file); - } - path->dentry = dentry; } else { @@ -5356,6 +5439,33 @@ SYSCALL_DEFINE3(mknod, const char __user , filename, umode_t, mode, unsigned, d return filename_mknodat(AT_FDCWD, name, mode, dev); } +static inline +struct dentry vfs_mkdir_no_perm(struct mnt_idmap idmap, struct inode dir, + struct dentry dentry, umode_t mode, + struct delegated_inode di) +{ + unsigned max_links = dir->i_sb->s_max_links; + struct dentry de; + int error; + + if (max_links && dir->i_nlink >= max_links) + return ERR_PTR(-EMLINK); + + error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, di); + if (error) + return ERR_PTR(error); + + de = dir->i_op->mkdir(idmap, dir, dentry, mode); + if (IS_ERR(de)) + return de; + if (de) { + dput(dentry); + dentry = de; + } + fsnotify_mkdir(dir, dentry); + return dentry; +} + /** * vfs_mkdir - create directory returning correct dentry if possible * @idmap: idmap of the mount the inode was found from @@ -5383,14 +5493,13 @@ struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir, struct delegated_inode delegated_inode) { int error; - unsigned max_links = dir->i_sb->s_max_links; struct dentry de; error = may_create_dentry(idmap, dir, dentry); if (error) goto err; - error = -EPERM; + error = -EOPNOTSUPP; if (!dir->i_op->mkdir) goto err; @@ -5399,24 +5508,12 @@ struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir, if (error) goto err; - error = -EMLINK; - if (max_links && dir->i_nlink >= max_links) + de = vfs_mkdir_no_perm(idmap, dir, dentry, mode, delegated_inode); + if (IS_ERR(de)) { + error = PTR_ERR(de); goto err; - - error = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode); - if (error) - goto err; - - de = dir->i_op->mkdir(idmap, dir, dentry, mode); - error = PTR_ERR(de); - if (IS_ERR(de)) - goto err; - if (de) { - dput(dentry); - dentry = de; } - fsnotify_mkdir(dir, dentry); - return dentry; + return de; err: end_creating(dentry); @@ -5703,7 +5800,7 @@ int filename_unlinkat(int dfd, struct filename name) goto exit_drop_write; / Why not before? Because we want correct error value / - if (unlikely(last.name[last.len])) { + if (unlikely(trailing_slashes(&last))) { if (d_is_dir(dentry)) error = -EISDIR; else @@ -6305,16 +6402,16 @@ int filename_renameat2(int olddfd, struct filename from, if (flags & RENAME_EXCHANGE) { if (!d_is_dir(rd.new_dentry)) { error = -ENOTDIR; - if (new_last.name[new_last.len]) + if (trailing_slashes(&new_last)) goto exit_unlock; } } /* unless the source is a directory trailing slashes give -ENOTDIR / if (!d_is_dir(rd.old_dentry)) { error = -ENOTDIR; - if (old_last.name[old_last.len]) + if (trailing_slashes(&old_last)) goto exit_unlock; - if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len]) + if (!(flags & RENAME_EXCHANGE) && trailing_slashes(&new_last)) goto exit_unlock; } diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index 49394123bd096..4b1404d6859e8 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2121,6 +2121,11 @@ int nfs_atomic_open(struct inode dir, struct dentry dentry, dfprintk(VFS, "NFS: atomic_open(%s/%llu), %pd\n", dir->i_sb->s_id, dir->i_ino, dentry); + if (O_IS_MKDIR(open_flags)) { + open_flags &= ~O_CREAT; + mode = 0; + } + err = nfs_check_flags(open_flags); if (err) return err; @@ -2317,6 +2322,11 @@ int nfs_atomic_open_v23(struct inode dir, struct dentry dentry, / int error = 0; + if (O_IS_MKDIR(open_flags)) { + open_flags &= ~O_CREAT; + mode = 0; + } + if (dentry->d_name.len > NFS_SERVER(dir)->namelen) return -ENAMETOOLONG; diff --git a/fs/open.c b/fs/open.c index 6b1c14e684a93..6cb5e2ad781f3 100644 --- a/fs/open.c +++ b/fs/open.c @@ -1239,29 +1239,30 @@ inline int build_open_flags(const struct open_how how, struct open_flags op) if (WILL_CREATE(flags)) { if (how->mode & ~S_IALLUGO) return -EINVAL; - op->mode = how->mode \| S_IFREG; + if (O_IS_MKDIR(flags)) + op->mode = how->mode \| S_IFDIR; + else + op->mode = how->mode \| S_IFREG; } else { if (how->mode != 0) return -EINVAL; op->mode = 0; } - /* - * Block bugs where O_DIRECTORY \| O_CREAT created regular files. - * Note, that blocking O_DIRECTORY \| O_CREAT here also protects - * O_TMPFILE below which requires O_DIRECTORY being raised. - / - if ((flags & (O_DIRECTORY \| O_CREAT)) == (O_DIRECTORY \| O_CREAT)) - return -EINVAL; - / Now handle the creative implementation of O_TMPFILE. / if (flags & __O_TMPFILE) { / * In order to ensure programs get explicit errors when trying * to use O_TMPFILE on old kernels we enforce that O_DIRECTORY - * is raised alongside __O_TMPFILE. + * is raised alongside __O_TMPFILE, but without O_CREAT. The + * reason for disallowing O_CREAT\|O_TMPFILE is that + * O_DIRECTORY\|O_CREAT used to work and created a regular file + * if nothing existed at the open path. Hence, allowing the + * combination would have caused O_CREAT\|O_TMPFILE to create a + * regular (non-temporary) file on old kernels, while the caller + * would believe they created an actual O_TMPFILE. / - if (!(flags & O_DIRECTORY)) + if (!(flags & O_DIRECTORY) \|\| (flags & O_CREAT)) return -EINVAL; if (!(acc_mode & MAY_WRITE)) return -EINVAL; @@ -1318,6 +1319,15 @@ inline int build_open_flags(const struct open_how how, struct open_flags op) op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN; + / + * Requesting write access on a directory can never succeed. Rather + * than performing a path-walk to determine whether the target is + * actually a directory (-EISDIR) or not (-ENOTDIR), we short-circuit + * to -ENOTDIR. + / + if ((flags & O_DIRECTORY) && !(flags & __O_TMPFILE) && (acc_mode & MAY_WRITE)) + return -ENOTDIR; + if (flags & O_CREAT) { op->intent \|= LOOKUP_CREATE; if (flags & O_EXCL) { diff --git a/fs/smb/client/dir.c b/fs/smb/client/dir.c index 6fa6d48fdfd30..f75095a48fdb1 100644 --- a/fs/smb/client/dir.c +++ b/fs/smb/client/dir.c @@ -534,6 +534,11 @@ int cifs_atomic_open(struct inode dir, struct dentry direntry, if (unlikely(cifs_forced_shutdown(cifs_sb))) return smb_EIO(smb_eio_trace_forced_shutdown); + if (O_IS_MKDIR(oflags)) { + oflags &= ~O_CREAT; + mode = 0; + } + / * Posix open is only called (at lookup time) for file create now. For * opens (rather than creates), because we do not know if it is a file diff --git a/fs/vboxsf/dir.c b/fs/vboxsf/dir.c index 0b9eab157432d..f20b61f6d8da7 100644 --- a/fs/vboxsf/dir.c +++ b/fs/vboxsf/dir.c @@ -318,6 +318,11 @@ static int vboxsf_dir_atomic_open(struct inode parent, struct dentry dentry, u64 handle; int err; + if (O_IS_MKDIR(flags)) { + flags &= ~O_CREAT; + mode = 0; + } + if (d_in_lookup(dentry)) { struct dentry res = vboxsf_dir_lookup(parent, dentry, 0); if (res \|\| d_really_is_positive(dentry)) diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h index 6ad6b9e7a226a..204e16bbe2634 100644 --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -30,6 +30,12 @@ / #define __O_REGULAR (1 << 30) +#define O_MKDIR_MASK (O_CREAT \| O_DIRECTORY) +static inline bool O_IS_MKDIR(unsigned int flags) +{ + return (flags & O_MKDIR_MASK) == O_MKDIR_MASK; +} + /* List of all valid flags for the how->resolve argument: / #define VALID_RESOLVE_FLAGS \ (RESOLVE_NO_XDEV \| RESOLVE_NO_MAGICLINKS \| RESOLVE_NO_SYMLINKS \| \ diff --git a/include/uapi/asm-generic/errno.h b/include/uapi/asm-generic/errno.h index bd78e69e0a43f..c84ebf89c8b6e 100644 --- a/include/uapi/asm-generic/errno.h +++ b/include/uapi/asm-generic/errno.h @@ -76,7 +76,7 @@ #define ENOPROTOOPT 92 / Protocol not available / #define EPROTONOSUPPORT 93 / Protocol not supported / #define ESOCKTNOSUPPORT 94 / Socket type not supported / -#define EOPNOTSUPP 95 / Operation not supported on transport endpoint / +#define EOPNOTSUPP 95 / Operation not supported / #define EPFNOSUPPORT 96 / Protocol family not supported / #define EAFNOSUPPORT 97 / Address family not supported by protocol / #define EADDRINUSE 98 / Address already in use / diff --git a/tools/testing/selftests/filesystems/.gitignore b/tools/testing/selftests/filesystems/.gitignore index 9eb185fb2f9dd..01c588d4c84f6 100644 --- a/tools/testing/selftests/filesystems/.gitignore +++ b/tools/testing/selftests/filesystems/.gitignore @@ -1,4 +1,5 @@ # SPDX-License-Identifier: GPL-2.0-only +open_o_creat_o_dir dnotify_test devpts_pts fclog diff --git a/tools/testing/selftests/filesystems/Makefile b/tools/testing/selftests/filesystems/Makefile index 03be337c1f351..0959bd26875ac 100644 --- a/tools/testing/selftests/filesystems/Makefile +++ b/tools/testing/selftests/filesystems/Makefile @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 CFLAGS += $(KHDR_INCLUDES) -TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test +TEST_GEN_PROGS := open_o_creat_o_dir devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test TEST_GEN_PROGS += idmapped_tmpfile TEST_GEN_PROGS_EXTENDED := dnotify_test diff --git a/tools/testing/selftests/filesystems/open_o_creat_o_dir.c b/tools/testing/selftests/filesystems/open_o_creat_o_dir.c new file mode 100644 index 0000000000000..538a7f7c58037 --- /dev/null +++ b/tools/testing/selftests/filesystems/open_o_creat_o_dir.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <sys/stat.h> +#include <errno.h> +#include <limits.h> +#include <fcntl.h> + +#include "kselftest_harness.h" +#include "wrappers.h" + +#define openat_o_mkdir_checked_flags(dfd, pathname, flags) ({ \ + struct stat __st; \ + int __fd = openat_o_mkdir(dfd, pathname, flags, S_IRWXU); \ + ASSERT_GE(__fd, 0); \ + ASSERT_EQ(fstat(__fd, &__st), 0); \ + EXPECT_TRUE(S_ISDIR(__st.st_mode)); \ + __fd; \ +}) + +#define openat_o_mkdir_checked(dfd, pathname) \ + openat_o_mkdir_checked_flags(dfd, pathname, O_RDONLY) + +FIXTURE(open_o_creat_o_dir) { + char dirpath[PATH_MAX]; + int dfd; +}; + +FIXTURE_SETUP(open_o_creat_o_dir) +{ + strcpy(self->dirpath, "/tmp/open_o_creat_o_dir_test.XXXXXX"); + ASSERT_NE(mkdtemp(self->dirpath), NULL); + self->dfd = open(self->dirpath, O_DIRECTORY); + ASSERT_GE(self->dfd, 0); +} + +FIXTURE_TEARDOWN(open_o_creat_o_dir) +{ + close(self->dfd); + rmdir(self->dirpath); +} + +/ Does open_o_creat_o_dir return a fd at all? / +TEST_F(open_o_creat_o_dir, returns_fd) +{ + int fd = openat_o_mkdir_checked(self->dfd, "newdir"); + EXPECT_EQ(close(fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "newdir", AT_REMOVEDIR), 0); +} + +/ The fd must refer to the directory that was just created. / +TEST_F(open_o_creat_o_dir, fd_is_created_dir) +{ + int fd; + struct stat st_via_fd, st_via_path; + char path[PATH_MAX]; + + fd = openat_o_mkdir_checked(self->dfd, "checkdir"); + + ASSERT_EQ(fstat(fd, &st_via_fd), 0); + + snprintf(path, sizeof(path), "%s/checkdir", self->dirpath); + ASSERT_EQ(stat(path, &st_via_path), 0); + + EXPECT_EQ(st_via_fd.st_ino, st_via_path.st_ino); + EXPECT_EQ(st_via_fd.st_dev, st_via_path.st_dev); + + EXPECT_EQ(close(fd), 0); + EXPECT_EQ(rmdir(path), 0); +} + +/ Missing parent component must fail with ENOENT. / +TEST_F(open_o_creat_o_dir, enoent_missing_parent) +{ + EXPECT_EQ(openat_o_mkdir(self->dfd, "nonexistent/child", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, ENOENT); +} + +/ An invalid dfd must fail with EBADF. / +TEST_F(open_o_creat_o_dir, ebadf) +{ + EXPECT_EQ(openat_o_mkdir(FD_INVALID, "badfdir", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, EBADF); +} + +/ A dfd that points to a file (not a directory) must fail with ENOTDIR. / +TEST_F(open_o_creat_o_dir, enotdir_dfd) +{ + int file_fd; + + file_fd = openat(self->dfd, "file", + O_CREAT \| O_RDONLY, S_IRWXU); + ASSERT_GE(file_fd, 0); + + EXPECT_EQ(openat_o_mkdir(file_fd, "subdir", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, ENOTDIR); + + EXPECT_EQ(close(file_fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "file", 0), 0); +} + +/ + * O_EXCL together with O_CREAT\|O_DIRECTORY should succeed if the target + * directory does not yet exist. After directory creation, repeating this + * call must fail with EEXIST, but should succeed if the O_EXCL is dropped. + / +TEST_F(open_o_creat_o_dir, o_excl_eexist) +{ + int excldir_fd; + + excldir_fd = openat_o_mkdir_checked_flags(self->dfd, "excldir", O_EXCL); + + EXPECT_EQ(openat_o_mkdir(self->dfd, "excldir", O_EXCL, S_IRWXU), -1); + EXPECT_EQ(errno, EEXIST); + + int excldir_reopen_fd = openat_o_mkdir_checked(self->dfd, "excldir"); + + EXPECT_EQ(close(excldir_reopen_fd), 0); + EXPECT_EQ(close(excldir_fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "excldir", AT_REMOVEDIR), 0); +} + +/ + * O_CREAT\|O_DIRECTORY on a path that already exists as a regular file + * must fail with ENOTDIR. + / +TEST_F(open_o_creat_o_dir, existing_file_enotdir) +{ + int file_fd; + + file_fd = openat(self->dfd, "regfile", + O_CREAT \| O_RDONLY, S_IRWXU); + ASSERT_GE(file_fd, 0); + EXPECT_EQ(close(file_fd), 0); + + EXPECT_EQ(openat_o_mkdir(self->dfd, "regfile", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, ENOTDIR); + + EXPECT_EQ(unlinkat(self->dfd, "regfile", 0), 0); +} + +/ + * O_CREAT\|O_DIRECTORY combined with a writable access mode must be + * rejected: a directory cannot be opened for writing. + / +TEST_F(open_o_creat_o_dir, rejects_writable_acc_mode) +{ + EXPECT_EQ(openat_o_mkdir(self->dfd, "rdwrdir", O_RDWR, S_IRWXU), -1); + EXPECT_EQ(errno, ENOTDIR); + / Clean up if the kernel created the directory anyway. / + unlinkat(self->dfd, "rdwrdir", AT_REMOVEDIR); +} + +/ + * openat(O_CREAT\|O_DIRECTORY) with a trailing slash should work. + / +TEST_F(open_o_creat_o_dir, trailing_slash) +{ + int fd = openat_o_mkdir_checked(self->dfd, "newdir/"); + EXPECT_EQ(close(fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "newdir", AT_REMOVEDIR), 0); +} + +/ + * openat(O_CREAT) with a trailing slash but without O_DIRECTORY + * must fail with EISDIR and must not create anything at the path. + / +TEST_F(open_o_creat_o_dir, trailing_slash_no_o_dir) +{ + int fd; + struct stat st; + + fd = openat(self->dfd, "trailing/", O_CREAT \| O_RDONLY, S_IRWXU); + EXPECT_EQ(fd, -1); + EXPECT_EQ(errno, EISDIR); + + EXPECT_EQ(fstatat(self->dfd, "trailing", &st, 0), -1); + EXPECT_EQ(errno, ENOENT); + + / Best-effort cleanup in case the kernel left a file behind. / + if (fd >= 0) + close(fd); + unlinkat(self->dfd, "trailing", 0); +} + +/ + * The returned fd must be usable as a dfd for further at() calls. + / +TEST_F(open_o_creat_o_dir, fd_usable_as_dfd) +{ + int parent_fd, child_fd; + char path[PATH_MAX]; + + parent_fd = openat_o_mkdir_checked(self->dfd, "parent"); + child_fd = openat_o_mkdir_checked(parent_fd, "child"); + + EXPECT_EQ(close(child_fd), 0); + EXPECT_EQ(close(parent_fd), 0); + + snprintf(path, sizeof(path), "%s/parent/child", self->dirpath); + EXPECT_EQ(rmdir(path), 0); + snprintf(path, sizeof(path), "%s/parent", self->dirpath); + EXPECT_EQ(rmdir(path), 0); +} + +/* + * O_CREAT\|O_DIRECTORY must refuse to create through a dangling trailing + * symlink, and must not create anything at the symlink target. + / +TEST_F(open_o_creat_o_dir, dangling_symlink_eexist) +{ + struct stat st; + + ASSERT_EQ(symlinkat("danglink_target", self->dfd, "danglink"), 0); + + EXPECT_EQ(openat_o_mkdir(self->dfd, "danglink", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, EEXIST); + + / Nothing must have been created at the target. / + EXPECT_EQ(fstatat(self->dfd, "danglink_target", &st, 0), -1); + EXPECT_EQ(errno, ENOENT); + + EXPECT_EQ(unlinkat(self->dfd, "danglink", 0), 0); +} + +/ + * A trailing symlink that resolves to an existing directory must still open. + / +TEST_F(open_o_creat_o_dir, symlink_not_dangling_ok) +{ + int fd; + + ASSERT_EQ(mkdirat(self->dfd, "realdir", 0700), 0); + ASSERT_EQ(symlinkat("realdir", self->dfd, "dirlink"), 0); + + / Trailing symlink resolving to an existing directory. / + fd = openat_o_mkdir_checked(self->dfd, "dirlink"); + EXPECT_EQ(close(fd), 0); + + EXPECT_EQ(unlinkat(self->dfd, "dirlink", 0), 0); + EXPECT_EQ(unlinkat(self->dfd, "realdir", AT_REMOVEDIR), 0); +} + +/ + * An O_CREAT\|O_DIRECTORY open of an existing directory owned by someone else, + * inside a sticky world-writable directory, must be refused. + / +TEST_F(open_o_creat_o_dir, sticky_dir_eacces) +{ + int sticky_fd, fd; + + if (geteuid() != 0) + SKIP(return, "needs root for fchownat"); + + ASSERT_EQ(mkdirat(self->dfd, "sticky", 01777), 0); + ASSERT_EQ(fchmodat(self->dfd, "sticky", 01777, 0), 0); + sticky_fd = openat(self->dfd, "sticky", O_DIRECTORY \| O_RDONLY); + ASSERT_GE(sticky_fd, 0); + + ASSERT_EQ(mkdirat(sticky_fd, "otherdir", 0700), 0); + if (fchownat(sticky_fd, "otherdir", 1, 1, 0)) { + int err = errno; + + unlinkat(sticky_fd, "otherdir", AT_REMOVEDIR); + close(sticky_fd); + unlinkat(self->dfd, "sticky", AT_REMOVEDIR); + SKIP(return, "cannot chown to uid 1: %s", strerror(err)); + } + + EXPECT_EQ(openat_o_mkdir(sticky_fd, "otherdir", O_RDONLY, S_IRWXU), -1); + EXPECT_EQ(errno, EACCES); + + / Without O_CREAT the very same open must still succeed. / + fd = openat(sticky_fd, "otherdir", O_DIRECTORY \| O_RDONLY); + EXPECT_GE(fd, 0); + if (fd >= 0) { + EXPECT_EQ(close(fd), 0); + } + + EXPECT_EQ(unlinkat(sticky_fd, "otherdir", AT_REMOVEDIR), 0); + EXPECT_EQ(close(sticky_fd), 0); + EXPECT_EQ(unlinkat(self->dfd, "sticky", AT_REMOVEDIR), 0); +} + +/ + * O_TMPFILE is encoded as __O_TMPFILE\|O_DIRECTORY. Now that O_CREAT is no + * longer rejected alongside O_DIRECTORY, O_TMPFILE\|O_CREAT must still be + * rejected explicitly so that it cannot create a persistent file on kernels + * that predate O_TMPFILE. + / +TEST_F(open_o_creat_o_dir, tmpfile_with_o_creat_einval) +{ + EXPECT_EQ(openat(self->dfd, ".", O_TMPFILE \| O_CREAT \| O_RDWR, S_IRWXU), + -1); + EXPECT_EQ(errno, EINVAL); +} + +TEST_HARNESS_MAIN diff --git a/tools/testing/selftests/filesystems/wrappers.h b/tools/testing/selftests/filesystems/wrappers.h index 420ae4f908cf2..abe5b85cebdcd 100644 --- a/tools/testing/selftests/filesystems/wrappers.h +++ b/tools/testing/selftests/filesystems/wrappers.h @@ -13,6 +13,10 @@ #define STATX_MNT_ID_UNIQUE 0x00004000U / Want/got extended stx_mount_id / #endif +#ifndef FD_INVALID +#define FD_INVALID -10009 +#endif + static inline int sys_fsopen(const char fsname, unsigned int flags) { return syscall(__NR_fsopen, fsname, flags); @@ -105,4 +109,11 @@ static inline int sys_open_tree(int dfd, const char filename, unsigned int flag return syscall(__NR_open_tree, dfd, filename, flags); } +static inline int openat_o_mkdir(int dfd, const char pathname, + unsigned int flags, mode_t mode) +{ + return syscall(__NR_openat, dfd, pathname, + flags \| O_DIRECTORY \| O_CREAT, mode); +} + #endif
41/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16134 output: 30 thoughts: 1905 Thoughts: Patch Analysis: Atomic Directory Creation Support Okay, let's dive into this patch. My initial thought is to carefully analyze the changes related to introducing `O_CREAT \| O_DIRECTORY` support within `open()` and `openat()` for atomic directory creation (or opening if it exists). First, I need to understand what's been touched, so I've looked at the list of files. That gives me a roadmap: fs/9p, ceph, fuse, gfs2, namei, nfs, open.c, smb, vboxsf, fcntl.h, and errno.h. Also, there are selftests, which is good for automated validation. Now I need to understand the code logic. In `fs/namei.c`, I see a lot of modifications related to handling the `O_CREAT` flag with directories. I'm noting the new helper functions like `may_o_create` and the re-factoring of `vfs_create_no_perm` and `vfs_mkdir_no_perm`. The `atomic_open` function has a specific handling for `O_IS_MKDIR` which is important, especially when the error is `-ENOENT`. Then `lookup_open` gets my attention because of the different paths it takes for `create_dir` where it uses the new `vfs_mkdir_no_perm`. I also observe that the atomic open handlers of the different filesystems, strip the `O_CREAT` flag and reset the mode, so that the handling does not default to regular file creation, which is good. The `build_open_flags` function in `fs/open.c` is also changed, mostly to remove some checks. Next, I need to evaluate the KMSAN implications. The documentation is very clear. Standard KASAN detects many bugs, so KMSAN should only be used if there is a risk of uninitialized memory usage. I need to scan for: kernel structures sent to userspace, conditional logic on uninitialized variables, complex data structures with uninitialized fields, or potential for accessing uninitialized bytes due to bounds issues. Otherwise, there is no need. Okay, let's look at `vfs_mkdir_no_perm` which takes `delegated_inode` as an argument. I also see that `lookup_open` calls the function `vfs_mkdir_no_perm`. That is a red flag. What is `delegated_inode` here? I must find out if this is initialized. Is it used to initialize something in user space? This is critical!
42/3	2026/09/13 19:53	tool	grepper	0m Args: { "Expression": "delegated_inode", "PathPrefix": "fs/namei.c" } Results: { "Output": "fs/namei.c=4184=int vfs_create_no_perm(struct mnt_idmap idmap, struct dentry dentry,\nfs/namei.c:4185:\t\t umode_t mode, struct delegated_inode di)\nfs/namei.c-4186-{\n--\nfs/namei.c=4216=int vfs_create(struct mnt_idmap idmap, struct dentry dentry, umode_t mode,\nfs/namei.c:4217:\t struct delegated_inode di)\nfs/namei.c-4218-{\n--\nfs/namei.c=4502=struct dentry vfs_mkdir_no_perm(struct mnt_idmap , struct inode , struct dentry ,\nfs/namei.c:4503:\t\t\t\t umode_t, struct delegated_inode );\nfs/namei.c-4504-/\n--\nfs/namei.c=4518=static struct dentry lookup_open(struct nameidata nd, struct file file,\n--\nfs/namei.c-4520-{\nfs/namei.c:4521:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-4522-\tstruct mnt_idmap idmap;\n--\nfs/namei.c-4658-\t\tstruct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode,\nfs/namei.c:4659:\t\t\t\t\t\t \u0026delegated_inode);\nfs/namei.c-4660-\t\terror = PTR_ERR_OR_ZERO(res);\n--\nfs/namei.c-4663-\t} else {\nfs/namei.c:4664:\t\terror = vfs_create_no_perm(idmap, dentry, mode, \u0026delegated_inode);\nfs/namei.c-4665-\t}\n--\nfs/namei.c-4678-\nfs/namei.c:4679:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c-4680-\t\t/ Must have come through out_dput: dentry is an ERR_PTR() /\nfs/namei.c:4681:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-4682-\n--\nfs/namei.c=5303=EXPORT_SYMBOL(dentry_create);\n--\nfs/namei.c-5311- @dev:\t\tdevice number of device to create\nfs/namei.c:5312: * @delegated_inode:\treturns parent inode, if the inode is delegated.\nfs/namei.c-5313- \n--\nfs/namei.c=5322=int vfs_mknod(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c-5323-\t struct dentry dentry, umode_t mode, dev_t dev,\nfs/namei.c:5324:\t struct delegated_inode delegated_inode)\nfs/namei.c-5325-{\n--\nfs/namei.c-5347-\nfs/namei.c:5348:\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode);\nfs/namei.c-5349-\tif (error)\n--\nfs/namei.c=5376=int filename_mknodat(int dfd, struct filename name, umode_t mode,\n--\nfs/namei.c-5378-{\nfs/namei.c:5379:\tstruct delegated_inode di = { };\nfs/namei.c-5380-\tstruct mnt_idmap idmap;\n--\nfs/namei.c=5443=struct dentry vfs_mkdir_no_perm(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c-5444-\t\t\t\t struct dentry dentry, umode_t mode,\nfs/namei.c:5445:\t\t\t\t struct delegated_inode di)\nfs/namei.c-5446-{\n--\nfs/namei.c-5474- * @mode:\t\tmode of the child directory\nfs/namei.c:5475: * @delegated_inode:\treturns parent inode, if the inode is delegated.\nfs/namei.c-5476- \n--\nfs/namei.c=5491=struct dentry vfs_mkdir(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c-5492-\t\t\t struct dentry dentry, umode_t mode,\nfs/namei.c:5493:\t\t\t struct delegated_inode delegated_inode)\nfs/namei.c-5494-{\n--\nfs/namei.c-5510-\nfs/namei.c:5511:\tde = vfs_mkdir_no_perm(idmap, dir, dentry, mode, delegated_inode);\nfs/namei.c-5512-\tif (IS_ERR(de)) {\n--\nfs/namei.c=5524=int filename_mkdirat(int dfd, struct filename name, umode_t mode)\n--\nfs/namei.c-5529-\tunsigned int lookup_flags = LOOKUP_DIRECTORY;\nfs/namei.c:5530:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-5531-\n--\nfs/namei.c-5540-\t\tdentry = vfs_mkdir(mnt_idmap(path.mnt), path.dentry-\u003ed_inode,\nfs/namei.c:5541:\t\t\t\t dentry, mode, \u0026delegated_inode);\nfs/namei.c-5542-\t\tif (IS_ERR(dentry))\n--\nfs/namei.c-5545-\tend_creating_path(\u0026path, dentry);\nfs/namei.c:5546:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c:5547:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-5548-\t\tif (!error)\n--\nfs/namei.c=5564=SYSCALL_DEFINE2(mkdir, const char __user , pathname, umode_t, mode)\n--\nfs/namei.c-5574- * @dentry:\t\tdentry of the child directory\nfs/namei.c:5575: * @delegated_inode:\treturns parent inode, if it's delegated.\nfs/namei.c-5576- \n--\nfs/namei.c=5585=int vfs_rmdir(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c:5586:\t struct dentry dentry, struct delegated_inode delegated_inode)\nfs/namei.c-5587-{\n--\nfs/namei.c-5607-\nfs/namei.c:5608:\terror = try_break_deleg(dir, LEASE_BREAK_DIR_DELETE, delegated_inode);\nfs/namei.c-5609-\tif (error)\n--\nfs/namei.c=5630=int filename_rmdir(int dfd, struct filename name)\n--\nfs/namei.c-5637-\tunsigned int lookup_flags = 0;\nfs/namei.c:5638:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-5639-retry:\n--\nfs/namei.c-5669-\terror = vfs_rmdir(mnt_idmap(path.mnt), path.dentry-\u003ed_inode,\nfs/namei.c:5670:\t\t\t dentry, \u0026delegated_inode);\nfs/namei.c-5671-exit4:\n--\nfs/namei.c-5676-\tpath_put(\u0026path);\nfs/namei.c:5677:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c:5678:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-5679-\t\tif (!error)\n--\nfs/namei.c=5689=SYSCALL_DEFINE1(rmdir, const char __user , pathname)\n--\nfs/namei.c-5699- @dentry:\tvictim\nfs/namei.c:5700: * @delegated_inode: returns victim inode, if the inode is delegated.\nfs/namei.c-5701- \n--\nfs/namei.c-5704- If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and\nfs/namei.c:5705: * return a reference to the inode in delegated_inode. The caller\nfs/namei.c-5706- * should then break the delegation on that inode and retry. Because\n--\nfs/namei.c-5709- \nfs/namei.c:5710: Alternatively, a caller may pass NULL for delegated_inode. This may\nfs/namei.c-5711- * be appropriate for callers that expect the underlying filesystem not\n--\nfs/namei.c=5720=int vfs_unlink(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c:5721:\t struct dentry dentry, struct delegated_inode delegated_inode)\nfs/namei.c-5722-{\n--\nfs/namei.c-5739-\t\tif (!error) {\nfs/namei.c:5740:\t\t\terror = try_break_deleg(dir, LEASE_BREAK_DIR_DELETE, delegated_inode);\nfs/namei.c-5741-\t\t\tif (error)\nfs/namei.c-5742-\t\t\t\tgoto out;\nfs/namei.c:5743:\t\t\terror = try_break_deleg(target, 0, delegated_inode);\nfs/namei.c-5744-\t\t\tif (error)\n--\nfs/namei.c=5774=int filename_unlinkat(int dfd, struct filename name)\n--\nfs/namei.c-5781-\tstruct inode inode;\nfs/namei.c:5782:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-5783-\tunsigned int lookup_flags = 0;\n--\nfs/namei.c-5816-\terror = vfs_unlink(mnt_idmap(path.mnt), path.dentry-\u003ed_inode,\nfs/namei.c:5817:\t\t\t dentry, \u0026delegated_inode);\nfs/namei.c-5818-exit_end_dirop:\n--\nfs/namei.c-5820-\tiput(inode);\t/* truncate the inode here /\nfs/namei.c:5821:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c:5822:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-5823-\t\tif (!error)\n--\nfs/namei.c=5848=SYSCALL_DEFINE1(unlink, const char __user , pathname)\n--\nfs/namei.c-5859- * @oldname:\tname of the file to link to\nfs/namei.c:5860: * @delegated_inode: returns victim inode, if the inode is delegated.\nfs/namei.c-5861- \n--\nfs/namei.c=5870=int vfs_symlink(struct mnt_idmap idmap, struct inode dir,\nfs/namei.c-5871-\t\tstruct dentry dentry, const char oldname,\nfs/namei.c:5872:\t\tstruct delegated_inode delegated_inode)\nfs/namei.c-5873-{\n--\nfs/namei.c-5886-\nfs/namei.c:5887:\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode);\nfs/namei.c-5888-\tif (error)\n--\nfs/namei.c=5898=int filename_symlinkat(struct filename from, int newdfd, struct filename to)\n--\nfs/namei.c-5903-\tunsigned int lookup_flags = 0;\nfs/namei.c:5904:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-5905-\n--\nfs/namei.c-5916-\t\terror = vfs_symlink(mnt_idmap(path.mnt), path.dentry-\u003ed_inode,\nfs/namei.c:5917:\t\t\t\t dentry, from-\u003ename, \u0026delegated_inode);\nfs/namei.c-5918-\tend_creating_path(\u0026path, dentry);\nfs/namei.c:5919:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c:5920:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-5921-\t\tif (!error)\n--\nfs/namei.c=5939=SYSCALL_DEFINE2(symlink, const char __user , oldname, const char __user , newname)\n--\nfs/namei.c-5951- * @new_dentry:\twhere to create the new link\nfs/namei.c:5952: * @delegated_inode: returns inode needing a delegation break\nfs/namei.c-5953- \n--\nfs/namei.c-5957- of breaking, it will return -EWOULDBLOCK and return a reference to the\nfs/namei.c:5958: * inode in delegated_inode. The caller should then break the delegation\nfs/namei.c-5959- * and retry. Because breaking a delegation may take a long time, the\n--\nfs/namei.c-5961- \nfs/namei.c:5962: Alternatively, a caller may pass NULL for delegated_inode. This may\nfs/namei.c-5963- * be appropriate for callers that expect the underlying filesystem not\n--\nfs/namei.c=5972=int vfs_link(struct dentry old_dentry, struct mnt_idmap idmap,\nfs/namei.c-5973-\t struct inode dir, struct dentry new_dentry,\nfs/namei.c:5974:\t struct delegated_inode delegated_inode)\nfs/namei.c-5975-{\n--\nfs/namei.c-6017-\telse {\nfs/namei.c:6018:\t\terror = try_break_deleg(dir, LEASE_BREAK_DIR_CREATE, delegated_inode);\nfs/namei.c-6019-\t\tif (!error)\nfs/namei.c:6020:\t\t\terror = try_break_deleg(inode, 0, delegated_inode);\nfs/namei.c-6021-\t\tif (!error)\n--\nfs/namei.c=6046=int filename_linkat(int olddfd, struct filename old,\n--\nfs/namei.c-6051-\tstruct path old_path, new_path;\nfs/namei.c:6052:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-6053-\tint how = 0;\n--\nfs/namei.c-6090-\terror = vfs_link(old_path.dentry, idmap, new_path.dentry-\u003ed_inode,\nfs/namei.c:6091:\t\t\t new_dentry, \u0026delegated_inode);\nfs/namei.c-6092-out_dput:\nfs/namei.c-6093-\tend_creating_path(\u0026new_path, new_dentry);\nfs/namei.c:6094:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c:6095:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-6096-\t\tif (!error) {\n--\nfs/namei.c=6119=SYSCALL_DEFINE2(link, const char __user , oldname, const char __user , newname)\n--\nfs/namei.c-6133- * the source or destination, it will return -EWOULDBLOCK and return a\nfs/namei.c:6134: * reference to the inode in delegated_inode. The caller should then\nfs/namei.c-6135- * break the delegation and retry. Because breaking a delegation may\n--\nfs/namei.c-6138- \nfs/namei.c:6139: Alternatively, a caller may pass NULL for delegated_inode. This may\nfs/namei.c-6140- * be appropriate for callers that expect the underlying filesystem not\n--\nfs/namei.c=6172=int vfs_rename(struct renamedata rd)\n--\nfs/namei.c-6178-\tstruct dentry new_dentry = rd-\u003enew_dentry;\nfs/namei.c:6179:\tstruct delegated_inode delegated_inode = rd-\u003edelegated_inode;\nfs/namei.c-6180-\tunsigned int flags = rd-\u003eflags;\n--\nfs/namei.c-6286-\t\t\t\t\t\t LEASE_BREAK_DIR_DELETE,\nfs/namei.c:6287:\t\t\t\tdelegated_inode);\nfs/namei.c-6288-\tif (error)\n--\nfs/namei.c-6290-\tif (new_dir != old_dir) {\nfs/namei.c:6291:\t\terror = try_break_deleg(new_dir, LEASE_BREAK_DIR_CREATE, delegated_inode);\nfs/namei.c-6292-\t\tif (error)\n--\nfs/namei.c-6295-\tif (!is_dir) {\nfs/namei.c:6296:\t\terror = try_break_deleg(source, 0, delegated_inode);\nfs/namei.c-6297-\t\tif (error)\n--\nfs/namei.c-6300-\tif (target \u0026\u0026 !new_is_dir) {\nfs/namei.c:6301:\t\terror = try_break_deleg(target, 0, delegated_inode);\nfs/namei.c-6302-\t\tif (error)\n--\nfs/namei.c=6344=int filename_renameat2(int olddfd, struct filename from,\n--\nfs/namei.c-6350-\tenum last_type old_type, new_type;\nfs/namei.c:6351:\tstruct delegated_inode delegated_inode = { };\nfs/namei.c-6352-\tunsigned int lookup_flags = 0;\n--\nfs/namei.c-6394-\trd.new_parent\t = new_path.dentry;\nfs/namei.c:6395:\trd.delegated_inode = \u0026delegated_inode;\nfs/namei.c-6396-\trd.flags\t = flags;\n--\nfs/namei.c-6426-exit_lock_rename:\nfs/namei.c:6427:\tif (is_delegated(\u0026delegated_inode)) {\nfs/namei.c:6428:\t\terror = break_deleg_wait(\u0026delegated_inode);\nfs/namei.c-6429-\t\tif (!error)\n" }
43/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23775 output: 35 thoughts: 89 Thoughts: Here's my summary, as I understand the code: Examining the Initialization of `delegated_inode` Okay, so I'm digging into how `lookup_open()` is handling delegated inodes. My understanding is that, at the outset, `delegated_inode` is initialized as an empty structure. I see that on line 4521, `struct delegated_inode delegated_inode = { };`. Now, I need to get a better grasp on how `lookup_open` utilizes the `dentry` and `create_dir` objects within this context. I'll need to go through the code, particularly `fs/namei.c`, and focus on lines 4630 through 4685 to see the interactions between those elements. That range should clarify how the structure and related routines behave in practice.
44/3	2026/09/13 19:53	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4630, "LineCount": 60 } Results: { "Contents": "4630:\t\t\t\tdentry = res;\n4631:\t\t\t}\n4632:\t\t}\n4633:\t\n4634:\t\tif (dentry-\u003ed_inode \|\| !(op-\u003eopen_flag \u0026 O_CREAT)) {\n4635:\t\t\t/\n4636:\t\t\t No need to create a file. If lookup returned a positive\n4637:\t\t\t * dentry, the file will be opened in do_open().\n4638:\t\t\t /\n4639:\t\t\tgoto out;\n4640:\t\t}\n4641:\t\n4642:\t\t/ Negative dentry with O_CREAT flag set /\n4643:\t\taudit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);\n4644:\t\n4645:\t\tif (unlikely(create_error)) {\n4646:\t\t\t/ should have done a create, but we already errored /\n4647:\t\t\terror = create_error;\n4648:\t\t\tgoto out_dput;\n4649:\t\t}\n4650:\t\n4651:\t\tif ((create_dir \u0026\u0026 !dir_inode-\u003ei_op-\u003emkdir)\n4652:\t\t\t\|\| (!create_dir \u0026\u0026 !dir_inode-\u003ei_op-\u003ecreate)) {\n4653:\t\t\terror = -EOPNOTSUPP;\n4654:\t\t\tgoto out_dput;\n4655:\t\t}\n4656:\t\n4657:\t\tif (create_dir) {\n4658:\t\t\tstruct dentry res = vfs_mkdir_no_perm(idmap, dir_inode, dentry, mode,\n4659:\t\t\t\t\t\t\t \u0026delegated_inode);\n4660:\t\t\terror = PTR_ERR_OR_ZERO(res);\n4661:\t\t\tif (!error)\n4662:\t\t\t\tdentry = res;\n4663:\t\t} else {\n4664:\t\t\terror = vfs_create_no_perm(idmap, dentry, mode, \u0026delegated_inode);\n4665:\t\t}\n4666:\t\tif (error)\n4667:\t\t\tgoto out_dput;\n4668:\t\n4669:\t\tfile-\u003ef_mode \|= FMODE_CREATED;\n4670:\tout:\n4671:\t\tif ((open_flag \u0026 O_CREAT) \|\| create_error)\n4672:\t\t\tinode_unlock(dir_inode);\n4673:\t\telse\n4674:\t\t\tinode_unlock_shared(dir_inode);\n4675:\t\n4676:\t\tif (got_write)\n4677:\t\t\tmnt_drop_write(nd-\u003epath.mnt);\n4678:\t\n4679:\t\tif (is_delegated(\u0026delegated_inode)) {\n4680:\t\t\t/* Must have come through out_dput: dentry is an ERR_PTR() */\n4681:\t\t\terror = break_deleg_wait(\u0026delegated_inode);\n4682:\t\n4683:\t\t\tif (!error)\n4684:\t\t\t\tgoto retry;\n4685:\t\t\tdentry = ERR_PTR(error);\n4686:\t\t}\n4687:\t\n4688:\t\treturn dentry;\n4689:\t\n" }
45/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24931 output: 43 thoughts: 340 Thoughts: Analyzing the `vfs_mkdir_no_perm` Function Okay, so I'm looking at this `vfs_mkdir_no_perm` function, and it seems pretty straightforward. It's handling the core logic of creating a directory without permission checks, which is typical for kernel-level operations. Let's break it down, I see a few key things here: `max_links` being checked, a lease break attempt... that's standard. The real interest is this call to `dir->i_op->mkdir`. Okay, I know that `i_op` is the inode operations struct. So, it's calling the file system specific `mkdir` operation via a function pointer. Wait, I need to know exactly what this `mkdir` returns. Is it a `struct dentry ` or an `int`? It's been a while since I looked at the definition in `include/linux/fs.h`. Yep, definitely `struct dentry (mkdir) (struct mnt_idmap , struct inode ,struct dentry ,umode_t);`. But I always double check file system operations. Let me look at the `struct inode_operations` to be sure. It always pays to be certain!
46/3	2026/09/13 19:53	tool	grepper	0m Error: no matches Args: { "Expression": "int \$\\mkdir\$\|struct dentry \\ \$\\mkdir\$", "PathPrefix": "include/linux/fs.h" } Results:* { "error": "no matches" }
47/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25596 output: 28 thoughts: 18 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Grep Hunt for mkdir in fs.h Alright, so I need to understand something related to directory creation, and my gut tells me to check `include/linux/fs.h`. That file is the central point for file system related definitions in the kernel, so a function like `mkdir` would likely have a related entry, or at least some relevant structures defined there. I'm going to reach for `grep` and search directly within `fs.h` for instances of the command or function, looking to get a jump start on where the critical declarations related to `mkdir` may be found. This should give me a solid starting point for deeper investigation.
48/3	2026/09/13 19:53	tool	grepper	0m Args: { "Expression": "mkdir", "PathPrefix": "include/linux/fs.h" } Results: { "Output": "include/linux/fs.h=1764=int vfs_create(struct mnt_idmap , struct dentry , umode_t,\ninclude/linux/fs.h-1765-\t struct delegated_inode );\ninclude/linux/fs.h:1766:struct dentry vfs_mkdir(struct mnt_idmap , struct inode ,\ninclude/linux/fs.h-1767-\t\t\t struct dentry , umode_t, struct delegated_inode );\n--\ninclude/linux/fs.h=1994=struct inode_operations {\n--\ninclude/linux/fs.h-2007-\t\t\tconst char );\ninclude/linux/fs.h:2008:\tstruct dentry (mkdir) (struct mnt_idmap , struct inode ,\ninclude/linux/fs.h-2009-\t\t\t\t struct dentry , umode_t);\n" }
49/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26028 output: 32 thoughts: 558 Thoughts: My Thoughts on `mkdir` and Dentry Handling Okay, let's break this down. My initial thought is that `mkdir` returns a `struct dentry *`, which is the entry point. It seems like the core operation is `dir->i_op->mkdir(...)`. The expected return is either NULL or an alias `dentry` upon success, or an `ERR_PTR` on failure. This is classic VFS behaviour. Peering into `vfs_mkdir_no_perm`, I see the logic: the call to the underlying `mkdir` occurs. If it returns an error, we bounce that back immediately. If it's successful, but returns a non-NULL `de`, it means we have an alias `dentry`, right? So `vfs_mkdir_no_perm` does a `dput(dentry)` on the original, then `dentry = de;` before returning `de`. The `fsnotify_mkdir` call is what triggers the signals to other file systems. Easy peasy. The interesting case is when it returns NULL. Then, `vfs_mkdir_no_perm` returns the original `dentry`. Now, examining the `lookup_open` code, things get a bit more interesting. We've got `vfs_mkdir_no_perm` called, and its result assigned to `res`. The `PTR_ERR_OR_ZERO(res)` part is important: if `res` is not an error (a valid pointer), that function returns 0 and `dentry` gets updated to `res`. If `res` is an error pointer (`ERR_PTR`), `PTR_ERR_OR_ZERO` returns the negative error number, and we're supposed to `goto out_dput`. However, it's concerning that if `res` is `ERR_PTR`, it would execute `dput(dentry)`. This is odd because `dentry` still points to the original. This is, however, correct behaviour. I have to make a note of this. If `res` is neither an error nor NULL, it’s an alias dentry; `de` was non-NULL. In that case, `vfs_mkdir_no_perm` already took care of it: `dput(dentry)` and then assignment, so `res` is `de`, and `dentry` should also be `de`. The interesting cases are when `mkdir` returns NULL, or returns an alias dentry. So the old code worked as it should. Finally, I need to check how all this plays out in `do_open`. Time to go read `fs/namei.c`.
50/3	2026/09/13 19:53	tool	grepper	0m Args: { "Expression": "static int do_open\\(", "PathPrefix": "fs/namei.c" } Results: { "Output": "fs/namei.c=4823=static const char open_last_lookups(struct nameidata nd,\n--\nfs/namei.c-4877- /\nfs/namei.c:4878:static int do_open(struct nameidata nd,\nfs/namei.c-4879-\t\t struct file file, const struct open_flags op)\n" }
51/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27302 output: 35 thoughts: 18 Thoughts: Here's a first-person summary, tailored as requested: Diving into `do_open` Okay, let's get down to brass tacks. I need to understand this open system call's inner workings, so the first stop is going to be `fs/namei.c`. Specifically, I want to refresh my memory on `do_open`. That's where the core logic of file opening is implemented. I know there are a lot of layers, and I want to refresh my memory of the control flow. I'll be looking for how it handles path resolution, access checks, flags, and interaction with the VFS. Let's see how they deal with the file creation flags, how they interact with the inode and dentry caches, and how this all ultimately leads to getting a file descriptor back to the user. I'll likely be paying close attention to the error handling as well; where can things go wrong, and how does the kernel report those problems? I'll probably be making mental notes on performance considerations. Is there any obvious room for optimization in the hot path of file opens? Okay, time to crack open the source code.
52/3	2026/09/13 19:53	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4880, "LineCount": 70 } Results: { "Contents": "4880:\t{\n4881:\t\tstruct mnt_idmap idmap;\n4882:\t\tint open_flag = op-\u003eopen_flag;\n4883:\t\tbool do_truncate;\n4884:\t\tint acc_mode;\n4885:\t\tint error;\n4886:\t\n4887:\t\tif (!(file-\u003ef_mode \u0026 (FMODE_OPENED \| FMODE_CREATED))) {\n4888:\t\t\terror = complete_walk(nd);\n4889:\t\t\tif (error)\n4890:\t\t\t\treturn error;\n4891:\t\t}\n4892:\t\tif (!(file-\u003ef_mode \u0026 FMODE_CREATED))\n4893:\t\t\taudit_inode(nd-\u003ename, nd-\u003epath.dentry, 0);\n4894:\t\tidmap = mnt_idmap(nd-\u003epath.mnt);\n4895:\t\tif (open_flag \u0026 O_CREAT) {\n4896:\t\t\tif ((open_flag \u0026 O_EXCL) \u0026\u0026 !(file-\u003ef_mode \u0026 FMODE_CREATED))\n4897:\t\t\t\treturn -EEXIST;\n4898:\t\t\tif (!(open_flag \u0026 O_DIRECTORY) \u0026\u0026 d_is_dir(nd-\u003epath.dentry))\n4899:\t\t\t\treturn -EISDIR;\n4900:\t\n4901:\t\t\terror = may_create_in_sticky(idmap, nd,\n4902:\t\t\t\t\t\t d_backing_inode(nd-\u003epath.dentry));\n4903:\t\t\tif (unlikely(error))\n4904:\t\t\t\treturn error;\n4905:\t\t}\n4906:\t\n4907:\t\tif ((open_flag \u0026 __O_REGULAR) \u0026\u0026 !d_is_reg(nd-\u003epath.dentry))\n4908:\t\t\treturn -EFTYPE;\n4909:\t\n4910:\t\tif ((nd-\u003eflags \u0026 LOOKUP_DIRECTORY) \u0026\u0026 !d_can_lookup(nd-\u003epath.dentry))\n4911:\t\t\treturn -ENOTDIR;\n4912:\t\n4913:\t\tdo_truncate = false;\n4914:\t\tacc_mode = op-\u003eacc_mode;\n4915:\t\tif (file-\u003ef_mode \u0026 FMODE_CREATED) {\n4916:\t\t\t/ Don't check for write permission, don't truncate /\n4917:\t\t\topen_flag \u0026= ~O_TRUNC;\n4918:\t\t\tacc_mode = 0;\n4919:\t\t} else if (d_is_reg(nd-\u003epath.dentry) \u0026\u0026 open_flag \u0026 O_TRUNC) {\n4920:\t\t\terror = mnt_want_write(nd-\u003epath.mnt);\n4921:\t\t\tif (error)\n4922:\t\t\t\treturn error;\n4923:\t\t\tdo_truncate = true;\n4924:\t\t}\n4925:\t\terror = may_open(idmap, \u0026nd-\u003epath, acc_mode, open_flag);\n4926:\t\tif (!error \u0026\u0026 !(file-\u003ef_mode \u0026 FMODE_OPENED))\n4927:\t\t\terror = vfs_open(\u0026nd-\u003epath, file);\n4928:\t\tif (!error)\n4929:\t\t\terror = security_file_post_open(file, op-\u003eacc_mode);\n4930:\t\tif (!error \u0026\u0026 do_truncate)\n4931:\t\t\terror = handle_truncate(idmap, file);\n4932:\t\tif (unlikely(error \u003e 0)) {\n4933:\t\t\tWARN_ON(1);\n4934:\t\t\terror = -EINVAL;\n4935:\t\t}\n4936:\t\tif (do_truncate)\n4937:\t\t\tmnt_drop_write(nd-\u003epath.mnt);\n4938:\t\treturn error;\n4939:\t}\n4940:\t\n4941:\t/\n4942:\t vfs_tmpfile - create tmpfile\n4943:\t * @idmap:\tidmap of the mount the inode was found from\n4944:\t * @parentpath:\tpointer to the path of the base directory\n4945:\t * @file:\tfile descriptor of the new tmpfile\n4946:\t * @mode:\tmode of the new tmpfile\n4947:\t \n4948:\t Create a temporary file.\n4949:\t *\n" }
53/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28726 output: 31 thoughts: 304 Thoughts: My Analysis of the `do_open` Function Okay, let's break down this `do_open` function. I'm focusing on how file creation and permissions are handled, given the context. First, I see the conditional block that deals with the `O_CREAT` flag. This is crucial for creating new files or potentially handling existing ones. Initially, there was a check `if (d_is_dir(nd->path.dentry)) return -EISDIR;`, which prevented creating a file if a directory with the same name existed. But now, that has been slightly changed with the addition of `!(open_flag & O_DIRECTORY)`. This is key; it ensures that we only return -EISDIR if we're not explicitly trying to create a directory with `O_DIRECTORY` set, and the target is a directory. Essentially, now we only error out if we are not intending to create a directory, but the path is indeed to one. Then, there's the `may_create_in_sticky` function call which seems to be about security for sticky bits. Good, that's important. Next, I see a section related to the `FMODE_CREATED` flag. If this flag is set, it means the file was just created. Interesting. Now, it's setting `open_flag &= ~O_TRUNC;` so that the file will not be truncated, and `acc_mode = 0`. Right, so if it's new, we're not going to truncate it, and we might not need to set any permissions. Now I need to look at what `may_open` is doing. This will be the next step to look into this function further.
54/3	2026/09/13 19:53	tool	grepper	0m Args: { "Expression": "int may_open\\(", "PathPrefix": "fs/namei.c" } Results: { "Output": "fs/namei.c=4259=bool may_open_dev(const struct path path)\n--\nfs/namei.c-4264-\nfs/namei.c:4265:static int may_open(struct mnt_idmap idmap, const struct path *path,\nfs/namei.c-4266-\t\t int acc_mode, int flag)\n" }
55/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29544 output: 35 thoughts: 18 Thoughts: Here's my take on the `may_open` function in `fs/namei.c`. I'm approaching this assuming a fairly deep understanding of VFS and file system internals. Diving into `may_open` in `fs/namei.c` Alright, let's get into this. My first thought is to understand its role in the overall name lookup and file opening process. `may_open` is a crucial check, right? It's the gatekeeper, deciding if we're even allowed to attempt an open on this particular path, based on various access control mechanisms. I immediately want to consider the context: we're likely in the midst of a `path_openat` or similar system call flow, somewhere in the VFS layer. I anticipate the function will be fed the `struct inode` representing the target file, the desired `flags` (O_RDWR, O_CREAT, etc.), and probably the calling `cred` (credentials, UID/GID information) and maybe even a `struct path` or `struct nameidata`. It has to consider how this user's credentials relate to the file's permissions, ownership, and any potential security module restrictions (SELinux, AppArmor, etc.). I'm thinking about the order of checks. It likely starts with basic permission checks. Does the user's effective UID/GID have the necessary read, write, or execute permissions on the inode? It'll probably call `inode_permission` or something similar, and I'd be looking closely at how that function interacts with the file system's permission bits (the traditional rwx bits). Then, it'll need to handle any special file attributes. Is the file immutable? Append-only? These are crucial flags that can override the standard permission checks. I'm also curious about how it interacts with the file system's implementation. For example, some file systems might have their own custom access control mechanisms, and `may_open` is the point where they can plug in their own checks. I'm also wondering if it has to deal with file locks or quotas at this point. That would depend on the system call path it's called from and where those checks are deemed most efficient. It's possible those checks happen higher up the call stack, but I'll need to confirm that. I'm also considering the implications of `O_TRUNC`. Truncating a file might require special permissions or checks compared to simply reading or writing to it. Overall, I'm expecting a function that orchestrates a series of permission checks, taking into account the file's attributes, the user's credentials, the requested flags, and possibly any security module hooks. The goal, clearly, is a granular decision about whether the requested open operation can proceed. I want to see how efficiently it handles all these potential factors and how it integrates with the overall VFS framework. Let's see how well it's designed.
56/3	2026/09/13 19:53	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 4265, "LineCount": 40 } Results: { "Contents": "4265:\tstatic int may_open(struct mnt_idmap idmap, const struct path path,\n4266:\t\t\t int acc_mode, int flag)\n4267:\t{\n4268:\t\tstruct dentry dentry = path-\u003edentry;\n4269:\t\tstruct inode inode = dentry-\u003ed_inode;\n4270:\t\tint error;\n4271:\t\n4272:\t\tif (!inode)\n4273:\t\t\treturn -ENOENT;\n4274:\t\n4275:\t\tswitch (inode-\u003ei_mode \u0026 S_IFMT) {\n4276:\t\tcase S_IFLNK:\n4277:\t\t\treturn -ELOOP;\n4278:\t\tcase S_IFDIR:\n4279:\t\t\tif (acc_mode \u0026 MAY_WRITE)\n4280:\t\t\t\treturn -EISDIR;\n4281:\t\t\tif (acc_mode \u0026 MAY_EXEC)\n4282:\t\t\t\treturn -EACCES;\n4283:\t\t\tbreak;\n4284:\t\tcase S_IFBLK:\n4285:\t\tcase S_IFCHR:\n4286:\t\t\tif (!may_open_dev(path))\n4287:\t\t\t\treturn -EACCES;\n4288:\t\t\tfallthrough;\n4289:\t\tcase S_IFIFO:\n4290:\t\tcase S_IFSOCK:\n4291:\t\t\tif (acc_mode \u0026 MAY_EXEC)\n4292:\t\t\t\treturn -EACCES;\n4293:\t\t\tflag \u0026= ~O_TRUNC;\n4294:\t\t\tbreak;\n4295:\t\tcase S_IFREG:\n4296:\t\t\tif ((acc_mode \u0026 MAY_EXEC) \u0026\u0026 path_noexec(path))\n4297:\t\t\t\treturn -EACCES;\n4298:\t\t\tbreak;\n4299:\t\tdefault:\n4300:\t\t\tVFS_BUG_ON_INODE(!IS_ANON_FILE(inode), inode);\n4301:\t\t}\n4302:\t\n4303:\t\terror = inode_permission(idmap, inode, MAY_OPEN \| acc_mode);\n4304:\t\tif (error)\n" }
57/3	2026/09/13 19:53	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30806 output: 30 thoughts: 2229 Thoughts: Analysis of O_DIRECTORY and O_CREAT with fsnotify Implications Alright, let's break this down. It seems the core issue revolves around how the kernel handles `openat(..., O_CREAT \| O_DIRECTORY \| O_RDONLY)` and its interaction with `fsnotify`. The standard practice is to use `openat(..., O_DIRECTORY \| O_RDONLY)` to open a directory, which is fine, but the patch is introducing the `O_CREAT` flag with `O_DIRECTORY`. First, I need to check the `fsnotify` calls. It appears that `fsnotify_mkdir` and `fsnotify_create` are appropriately triggered, but their placement is crucial. The original code in `lookup_open` had `fsnotify_create` and `fsnotify_open` calls, but they've been removed. However, now they are called in `vfs_mkdir_no_perm` via `fsnotify_mkdir` and in `vfs_create_no_perm` via `fsnotify_create`. So that looks alright. `fsnotify_open` looks to be still called appropriately in `vfs_open()` or `atomic_open()`. The filesystems that don't support atomic mkdir are stripping `O_CREAT` and doing a lookup. In `atomic_open`, if the filesystem doesn't support the combined `O_CREAT \| O_DIRECTORY` it's stripping `O_CREAT` and returning an error. Now, let's explore if there are any data structures or memory buffers being allocated, copied, returned to userspace, or read without initialization. I need to make sure there aren't any potential vulnerabilities related to uninitialized memory access. I then went over the changed files to verify the behaviour of `O_IS_MKDIR` in the different filesystems, and I am fairly certain that this is functioning correctly. Next, I delved into the `lookup_open` code path. Specifically, I considered whether the directory already exists or not. If it does exist, it simply goes to `do_open`. If it doesn't exist and `O_CREAT` is requested, it calls `vfs_mkdir_no_perm`, which creates the directory and sets `file->f_mode \|= FMODE_CREATED;`. And then the function returns. `may_open` is called after this and then `vfs_open` is called to open the directory. This behavior seems standard. I examined `build_open_flags` and how the `how` and `op` structures are initialized. It appears everything is getting set properly, with no apparent data corruption or uninitialized memory concerns. Then `may_o_create` checks the security concerns on creation, and everything there looks good. Finally, I got concerned about out-of-bounds reads in `trailing_slashes` via `last->name[last->len]`. I need to review how `hash_name` and `last` are used in `namei.c` to fully assess this. This is the next thing to verify, and may indicate a memory safety issue.
58/3	2026/09/13 19:54	tool	grepper	0m Args: { "Expression": "hash_name\\(", "PathPrefix": "fs/namei.c" } Results: { "Output": "fs/namei.c=2396=static inline unsigned int fold_hash(unsigned long x, unsigned long y)\n--\nfs/namei.c-2405- * Return the hash of a string of known length. This is carfully\nfs/namei.c:2406: * designed to match hash_name(), which is the more critical function.\nfs/namei.c-2407- * In particular, we must end by hashing a final word containing 0..7\nfs/namei.c:2408: * payload bytes, to match the way that hash_name() iterates until it\nfs/namei.c-2409- * finds the delimiter after the name.\n--\nfs/namei.c=2454=EXPORT_SYMBOL(hashlen_string);\n--\nfs/namei.c-2465- /\nfs/namei.c:2466:static inline const char hash_name(struct nameidata nd,\nfs/namei.c-2467-\t\t\t\t const char name,\n--\nfs/namei.c=2549=EXPORT_SYMBOL(hashlen_string);\n--\nfs/namei.c-2554- /\nfs/namei.c:2555:static inline const char hash_name(struct nameidata nd, const char name, unsigned long lastword)\nfs/namei.c-2556-{\n--\nfs/namei.c=2592=static int link_path_walk(const char name, struct nameidata nd)\n--\nfs/namei.c-2622-\t\tnd-\u003elast.name = name;\nfs/namei.c:2623:\t\tname = hash_name(nd, name, \u0026lastword);\nfs/namei.c-2624-\n--\nfs/namei.c=2798=static inline bool trailing_slashes(const struct qstr last)\nfs/namei.c-2799-{\nfs/namei.c:2800:\t/* last-\u003elen is set by hash_name() to the length of the current\nfs/namei.c-2801-\t * component -\u003ename, terminating with '/' or a NUL character. */\n" }
59/3	2026/09/13 19:54	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34304 output: 31 thoughts: 1144 Thoughts: Analysis of Code Changes in a File System Context Okay, so I'm looking at this diff and immediately I see a pattern: the code is consistently replacing direct array access `x.name[x.len]` with a helper function, `trailing_slashes(&x)`. It's pretty clear this is just a code cleanup, making the intention clearer, and replacing potentially error-prone explicit indexing. This helper function is used to check if the path ends with trailing slashes. Next, I'm checking the changes to `lookup_open`. The biggest change here seems to be how directory creation is handled. It looks like they're trying to improve error handling or separate permissions checks more clearly. Instead of a combined `create` function, it now uses `vfs_mkdir_no_perm` or `vfs_create_no_perm` based on `create_dir`. This feels like a refactoring to potentially simplify the logic and separate directory creation from normal file creation. The `FMODE_CREATED` flag is still being set, which is crucial for indicating that the file or directory was newly created. Then I start wondering about the potential security implications. I'm thinking, "Is there anything concerning with the addition of `create_dir`?" I need to make sure I don't introduce a race condition with any checks. So I jump to `audit_log_path_denied` to ensure nothing untoward is occurring during creation. I see a string `"sticky_create_dir"` which tells me a bit about how the access is handled. I also check about `audit_inode_child`, but the call remains the same. Now I do a much more thorough check for security vulnerabilities. I'm going through my mental checklist: 1. User-space data exposure: The changes do not expose any kernel data structures to userspace, which is good. The open syscall returns a file descriptor. 2. Uninitialized variable use: I scan the code for conditional logic that depends on unitialized variables, but everything seems initialized, including `delegated_inode` which is initialized to `{}`. That's good. 3. Uninitialized data structures: Allocation of complex data structures with uninitialized fields is not happening here. 4. Buffer overflows/underflows: There's nothing here that allows accessing uninitialized parts of a buffer. To satisfy myself entirely, I consider what happens when a directory is opened, since there are subtle differences to note: When opening a directory, the `nd->path` points to the directory inode, `may_open` checks permissions, and `vfs_open` then calls `inode->i_fop->open`. It's all consistent whether or not we are creating the directory via `O_CREAT` (which results in `vfs_mkdir_no_perm` being called in this patch). The `struct file` is initialized via `alloc_empty_file()`. I am pretty confident that `path_openat` and surrounding VFS code is not modified here. So, overall, this seems like a relatively safe refactoring. It improves clarity with the `trailing_slashes` helper and separates directory creation logic but doesn't introduce any obvious security vulnerabilities. No significant functional or security issues are apparent here.
60/3	2026/09/13 19:54	tool	grepper	0m Args: { "Expression": "path_openat\\(", "PathPrefix": "fs/namei.c" } Results: { "Output": "fs/namei.c=5058=static int do_o_path(struct nameidata nd, unsigned flags, struct file file)\n--\nfs/namei.c-5069-\nfs/namei.c:5070:static struct file path_openat(struct nameidata nd,\nfs/namei.c-5071-\t\t\tconst struct open_flags op, unsigned flags)\n--\nfs/namei.c=5109=struct file do_file_open(int dfd, struct filename pathname,\n--\nfs/namei.c-5118-\tset_nameidata(\u0026nd, dfd, pathname, NULL);\nfs/namei.c:5119:\tfilp = path_openat(\u0026nd, op, flags \| LOOKUP_RCU);\nfs/namei.c-5120-\tif (unlikely(filp == ERR_PTR(-ECHILD)))\nfs/namei.c:5121:\t\tfilp = path_openat(\u0026nd, op, flags);\nfs/namei.c-5122-\tif (unlikely(filp == ERR_PTR(-ESTALE)))\nfs/namei.c:5123:\t\tfilp = path_openat(\u0026nd, op, flags \| LOOKUP_REVAL);\nfs/namei.c-5124-\trestore_nameidata();\n--\nfs/namei.c=5128=struct file do_file_open_root(const struct path *root,\n--\nfs/namei.c-5142-\tset_nameidata(\u0026nd, -1, filename, root);\nfs/namei.c:5143:\tfile = path_openat(\u0026nd, op, flags \| LOOKUP_RCU);\nfs/namei.c-5144-\tif (unlikely(file == ERR_PTR(-ECHILD)))\nfs/namei.c:5145:\t\tfile = path_openat(\u0026nd, op, flags);\nfs/namei.c-5146-\tif (unlikely(file == ERR_PTR(-ESTALE)))\nfs/namei.c:5147:\t\tfile = path_openat(\u0026nd, op, flags \| LOOKUP_REVAL);\nfs/namei.c-5148-\trestore_nameidata();\n" }
61/3	2026/09/13 19:54	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36764 output: 35 thoughts: 10 Thoughts: Okay, here's my summary, taking on the persona you requested: Deconstructing `path_openat` Alright, let's dive in. The task before me, as I understand it, is to dissect the function `path_openat`. Given my experience, I'm expecting this to be a core piece of the filesystem interaction puzzle, likely dealing with how we actually get a file descriptor for a given path relative to a directory file descriptor. It's almost certain this function will be handling the intricacies of path resolution, permission checks (at least at some level), and interacting with the underlying VFS layer. I'll be looking for how it handles things like symbolic links, the various flags that control file opening behavior (read/write modes, creation flags, etc.), and how it interacts with the inode/dentry caches for optimization. Essentially, I'm expecting a carefully layered function that bridges the userspace request with the kernel's internal representation of the filesystem structure. I'm keen to see how this function elegantly handles all the potential edge cases and security considerations involved. Time to get my hands dirty.
62/3	2026/09/13 19:54	tool	read-file	0m Args: { "File": "fs/namei.c", "FirstLine": 5068, "LineCount": 40 } Results: { "Contents": "5068:\t}\n5069:\t\n5070:\tstatic struct file path_openat(struct nameidata nd,\n5071:\t\t\t\tconst struct open_flags op, unsigned flags)\n5072:\t{\n5073:\t\tstruct file file;\n5074:\t\tint error;\n5075:\t\n5076:\t\tfile = alloc_empty_file(op-\u003eopen_flag, current_cred());\n5077:\t\tif (IS_ERR(file))\n5078:\t\t\treturn file;\n5079:\t\n5080:\t\tif (unlikely(file-\u003ef_flags \u0026 __O_TMPFILE)) {\n5081:\t\t\terror = do_tmpfile(nd, flags, op, file);\n5082:\t\t} else if (unlikely(file-\u003ef_flags \u0026 O_PATH)) {\n5083:\t\t\terror = do_o_path(nd, flags, file);\n5084:\t\t} else {\n5085:\t\t\tconst char *s = path_init(nd, flags);\n5086:\t\t\twhile (!(error = link_path_walk(s, nd)) \u0026\u0026\n5087:\t\t\t (s = open_last_lookups(nd, file, op)) != NULL)\n5088:\t\t\t\t;\n5089:\t\t\tif (!error)\n5090:\t\t\t\terror = do_open(nd, file, op);\n5091:\t\t\tterminate_walk(nd);\n5092:\t\t}\n5093:\t\tif (likely(!error)) {\n5094:\t\t\tif (likely(file-\u003ef_mode \u0026 FMODE_OPENED))\n5095:\t\t\t\treturn file;\n5096:\t\t\tWARN_ON(1);\n5097:\t\t\terror = -EINVAL;\n5098:\t\t}\n5099:\t\tfput_close(file);\n5100:\t\tif (error == -EOPENSTALE) {\n5101:\t\t\tif (flags \u0026 LOOKUP_RCU)\n5102:\t\t\t\terror = -ECHILD;\n5103:\t\t\telse\n5104:\t\t\t\terror = -ESTALE;\n5105:\t\t}\n5106:\t\treturn ERR_PTR(error);\n5107:\t}\n" }
63/3	2026/09/13 19:54	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37633 output: 321 thoughts: 1047 Thoughts: KMSAN Assessment: No New Risks Introduced Alright, let's break this down. My initial assessment of `alloc_empty_file` is that it's standard VFS lifecycle stuff, using either the slab cache or `kzalloc`. No red flags there. Now, let's dig into `dentry_create` in `fs/namei.c`. The key change is that `may_o_create` now takes `flags` instead of just `mode`. I need to make sure this doesn't introduce any issues, so let's verify how that `flags` value is used and initialized. First, I checked all callers of `may_o_create`. Both `lookup_open` and `dentry_create` pass their respective open flags, `open_flag` and `flags`, which are fully initialized integers, so that's good. Next, I looked at `o_create_mode`. It uses `vfs_prepare_mode`, which, from what I can see, is a pure function. It's safe since it just takes the inputs and calculates the output value of `umode_t`. Nothing to worry about. Now, let's address the questions: * Uninitialized memory risks? No. I see no uninitialized variables, no uninitialized heap or stack memory being exposed, and no information leaking to user space. It all looks clean. * Out-of-bounds, concurrency, or locking bugs? As far as locking is concerned, the code uses `inode_lock_nested(dir_inode, I_MUTEX_PARENT)` when `open_flag & O_CREAT`. LOCKDEP should catch any lock issues, and KASAN should handle any memory bounds or use-after-free issues with dentries/inodes. KMSAN won't catch any new bugs. KMSAN only catches reads of uninitialized memory, copying of uninitialized memory to user space, etc. I'm not seeing any new introduction of those in this patch. My conclusion is that this patch doesn't introduce any new KMSAN concerns. Let me structure my KMSAN reasoning concisely: 1. Purpose: The patch introduces support for atomically opening and creating directories using `O_CREAT \| O_DIRECTORY`. 2. Changes: Modifications across multiple files to handle `O_CREAT \| O_DIRECTORY` flags. These include `build_open_flags`, `may_o_create`, `o_create_mode`, and various network filesystem hooks. 3. KMSAN/KASAN Applicability: KMSAN detects reads of uninitialized memory. The patch doesn't introduce any such allocations, leaks, or uninitialized structure accesses. All variables are explicitly initialized. KASAN and LOCKDEP will cover any other potential issues. 4. Conclusion: No dedicated KMSAN fuzzing session is needed. I'm comfortable with that assessment. I'll flag `NeedsKMSAN: false` and move on. Time to call `set-results`.
64/3	2026/09/13 19:54	tool	set-results	0m Args: { "KMSANReasoning": "The patch series adds support for creating directories via open/openat using the `O_CREAT \| O_DIRECTORY` flag combination. The changes encompass:\n1. Validating and setting flags/modes in `build_open_flags()` (`fs/open.c`) to permit `O_CREAT \| O_DIRECTORY` with `S_IFDIR`.\n2. Refactoring VFS directory creation helpers (`vfs_mkdir_no_perm`) and directory creation permission checks (`may_o_create`, `may_create_in_sticky`) in `fs/namei.c`.\n3. Updating `atomic_open` implementations across various filesystems (9p, ceph, fuse, gfs2, nfs, smb, vboxsf) to strip `O_CREAT` when `O_DIRECTORY` is specified and fall back gracefully.\n\nNone of the changes allocate uninitialized heap/stack memory, copy kernel structures to user space, alter length/bounds checks on buffers, or read uninitialized struct fields or variables. All local variables (including `struct delegated_inode`) are zero-initialized. Potential issues arising from these changes (such as dentry/inode reference counting bugs, use-after-free, locking order inconsistencies, or NULL pointer dereferences) are fully covered by standard KASAN and LOCKDEP detectors. Therefore, a dedicated KMSAN fuzzing session is not justified.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch series adds support for creating directories via open/openat using the `O_CREAT \| O_DIRECTORY` flag combination. The changes encompass:\n1. Validating and setting flags/modes in `build_open_flags()` (`fs/open.c`) to permit `O_CREAT \| O_DIRECTORY` with `S_IFDIR`.\n2. Refactoring VFS directory creation helpers (`vfs_mkdir_no_perm`) and directory creation permission checks (`may_o_create`, `may_create_in_sticky`) in `fs/namei.c`.\n3. Updating `atomic_open` implementations across various filesystems (9p, ceph, fuse, gfs2, nfs, smb, vboxsf) to strip `O_CREAT` when `O_DIRECTORY` is specified and fall back gracefully.\n\nNone of the changes allocate uninitialized heap/stack memory, copy kernel structures to user space, alter length/bounds checks on buffers, or read uninitialized struct fields or variables. All local variables (including `struct delegated_inode`) are zero-initialized. Potential issues arising from these changes (such as dentry/inode reference counting bugs, use-after-free, locking order inconsistencies, or NULL pointer dereferences) are fully covered by standard KASAN and LOCKDEP detectors. Therefore, a dedicated KMSAN fuzzing session is not justified.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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