AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/08/29 22:23	flow	patch-triage	1m Args: null Results: { "EnableConfigs": [ "SECURITY", "SECURITY_SELINUX", "SECURITY_NETWORK", "AUDIT", "NET", "INET", "OVERLAY_FS" ], "FocusSymbols": [ "selinux_backing_file_alloc", "selinux_backing_file_free", "selinux_file_mprotect", "security_backing_file_alloc", "security_backing_file_free", "security_file_mprotect" ], "KMSANReasoning": "The patch extends SELinux backing file tracking to handle multiple layers in stacked filesystems (such as overlayfs and erofs) by introducing intermediate backing layer structures, recording paths and SIDs, and validating mounter permissions during file mmap/mprotect operations.\n\nAll newly allocated heap structures (`backing_file_security_layer` arrays) are explicitly and fully initialized upon allocation before use or copying. The containing `backing_file_security_struct` blob is allocated via `kmem_cache_zalloc`. The audit data stack structure `struct common_audit_data ad` is properly configured with `type = LSM_AUDIT_DATA_PATH` and the path union member assigned before passing to the audit/AVC subsystem. No data is exposed or copied to user space, and there is no branching on uninitialized memory. Potential risks in this patch (such as lifetime issues, refcounting, path management, or out-of-bounds indexing) fall within the scope of KASAN rather than KMSAN.", "NeedsKMSAN": false, "Reasoning": "The patch adds support for tracking and enforcing SELinux permissions across multi-layer backing files (such as those used by overlayfs and erofs). It implements dynamic allocation and reference tracking of intermediate backing file layers in selinux_backing_file_alloc, cleanup in selinux_backing_file_free, and multi-layer permission checks during mprotect in selinux_file_mprotect. These changes modify core security and filesystem interactions and are well worth fuzzing.", "WorthFuzzing": true }
1/1	2026/08/29 22:23	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit fa7a0b550622c645d62cf9a36498a7cabd726cb6\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Sat Aug 29 22:23:21 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/security/selinux/hooks.c b/security/selinux/hooks.c\nindex 035aaf113d1da..b6750edcc4783 100644\n--- a/security/selinux/hooks.c\n+++ b/security/selinux/hooks.c\n@@ -1674,26 +1674,32 @@ static int cred_has_capability(const struct cred cred,\n \treturn rc;\n }\n \n-/ Check whether a task has a particular permission to an inode.\n- The 'adp' parameter is optional and allows other audit\n- data to be passed (e.g. the dentry). /\n-static int inode_has_perm(const struct cred cred,\n-\t\t\t struct inode inode,\n-\t\t\t u32 perms,\n-\t\t\t struct common_audit_data adp)\n+/\n+ Check whether a SID has a particular permission to an inode. The 'adp'\n+ * parameter is optional and allows other audit data to be passed (e.g. the\n+ * dentry).\n+ /\n+static int inode_sid_has_perm(u32 sid, struct inode inode, u32 perms,\n+\t\t\t struct common_audit_data adp)\n {\n \tstruct inode_security_struct isec;\n-\tu32 sid;\n \n \tif (unlikely(IS_PRIVATE(inode)))\n \t\treturn 0;\n \n-\tsid = cred_sid(cred);\n \tisec = selinux_inode(inode);\n \n \treturn avc_has_perm(sid, isec-\u003esid, isec-\u003esclass, perms, adp);\n }\n \n+static int inode_has_perm(const struct cred cred,\n+\t\t\t struct inode inode,\n+\t\t\t u32 perms,\n+\t\t\t struct common_audit_data adp)\n+{\n+\treturn inode_sid_has_perm(cred_sid(cred), inode, perms, adp);\n+}\n+\n / Same as inode_has_perm, but pass explicit audit data containing\n the dentry to help the auditing code to more easily generate the\n pathname if needed. /\n@@ -3843,17 +3849,74 @@ static int selinux_file_alloc_security(struct file file)\n \treturn 0;\n }\n \n+static inline u32 selinux_file_user_sid(const struct file file)\n+{\n+\tif (unlikely(file-\u003ef_mode \u0026 FMODE_BACKING))\n+\t\treturn selinux_backing_file(file)-\u003euf_sid;\n+\treturn selinux_file(file)-\u003esid;\n+}\n+\n static int selinux_backing_file_alloc(struct file backing_file,\n \t\t\t\t const struct file user_file)\n {\n \tstruct backing_file_security_struct bfsec;\n+\tconst struct backing_file_security_struct ubfsec;\n+\tstruct backing_file_security_layer layer;\n+\tu32 i;\n \n \tbfsec = selinux_backing_file(backing_file);\n-\tbfsec-\u003euf_sid = selinux_file(user_file)-\u003esid;\n+\tbfsec-\u003euf_sid = selinux_file_user_sid(user_file);\n+\tif (!(user_file-\u003ef_mode \u0026 FMODE_BACKING))\n+\t\treturn 0;\n+\n+\tubfsec = selinux_backing_file(user_file);\n+\t/* a wrapped count would make kmalloc_array() return ZERO_SIZE_PTR /\n+\tif (unlikely(ubfsec-\u003elayer_count == U32_MAX))\n+\t\treturn -EOVERFLOW;\n+\n+\t/\n+\t * The final VMA only retains the lowest backing file, so record the\n+\t * whole chain here rather than in the mmap hook, where concurrent\n+\t * mappings would have to be serialized. Size it dynamically: erofs\n+\t * inode sharing adds a backing file without bumping s_stack_depth.\n+\t /\n+\tbfsec-\u003elayers = kmalloc_array(ubfsec-\u003elayer_count + 1,\n+\t\t\t\t sizeof(bfsec-\u003elayers), GFP_KERNEL);\n+\tif (!bfsec-\u003elayers)\n+\t\treturn -ENOMEM;\n+\n+\tfor (i = 0; i \u003c ubfsec-\u003elayer_count; i++) {\n+\t\tlayer = \u0026bfsec-\u003elayers[i];\n+\t\tlayer = ubfsec-\u003elayers[i];\n+\t\tpath_get(\u0026layer-\u003epath);\n+\t}\n+\n+\t/ f_path, not file_user_path(): this layer, not the top-level file /\n+\tlayer = \u0026bfsec-\u003elayers[i];\n+\tlayer-\u003epath = user_file-\u003ef_path;\n+\tlayer-\u003emounter_sid = cred_sid(user_file-\u003ef_cred);\n+\tlayer-\u003efd_sid = selinux_file(user_file)-\u003esid;\n+\tpath_get(\u0026layer-\u003epath);\n+\tbfsec-\u003elayer_count = ubfsec-\u003elayer_count + 1;\n \n \treturn 0;\n }\n \n+static void selinux_backing_file_free(struct file backing_file)\n+{\n+\tstruct backing_file_security_struct bfsec;\n+\n+\t/ security_backing_file_free() may be called twice after an error /\n+\tif (!backing_file_security(backing_file))\n+\t\treturn;\n+\n+\tbfsec = selinux_backing_file(backing_file);\n+\twhile (bfsec-\u003elayer_count)\n+\t\tpath_put(\u0026bfsec-\u003elayers[--bfsec-\u003elayer_count].path);\n+\tkfree(bfsec-\u003elayers);\n+\tbfsec-\u003elayers = NULL;\n+}\n+\n /\n * Check whether a task has the ioctl permission and cmd\n * operation to an inode.\n@@ -3971,6 +4034,53 @@ static int selinux_file_ioctl_compat(struct file file, unsigned int cmd,\n \n static int default_noexec __ro_after_init;\n \n+static u32 file_map_prot_to_av(unsigned long prot, bool shared)\n+{\n+\tu32 av = FILE__READ;\n+\n+\tif (shared \u0026\u0026 (prot \u0026 PROT_WRITE))\n+\t\tav \|= FILE__WRITE;\n+\tif (prot \u0026 PROT_EXEC)\n+\t\tav \|= FILE__EXECUTE;\n+\n+\treturn av;\n+}\n+\n+static int backing_mounters_has_perm(const struct file file, u32 av)\n+{\n+\tconst struct backing_file_security_struct bfsec;\n+\tconst struct backing_file_security_layer layer;\n+\tstruct common_audit_data ad;\n+\tstruct inode inode;\n+\tu32 i;\n+\tint rc;\n+\n+\tif (WARN_ON_ONCE(!(file-\u003ef_mode \u0026 FMODE_BACKING)))\n+\t\treturn -EIO;\n+\n+\tbfsec = selinux_backing_file(file);\n+\tfor (i = 0; i \u003c bfsec-\u003elayer_count; i++) {\n+\t\tlayer = \u0026bfsec-\u003elayers[i];\n+\t\tinode = d_inode(layer-\u003epath.dentry);\n+\n+\t\tad.type = LSM_AUDIT_DATA_PATH;\n+\t\tad.u.path = layer-\u003epath;\n+\n+\t\tif (layer-\u003emounter_sid != layer-\u003efd_sid) {\n+\t\t\trc = avc_has_perm(layer-\u003emounter_sid, layer-\u003efd_sid,\n+\t\t\t\t\t SECCLASS_FD, FD__USE, \u0026ad);\n+\t\t\tif (rc)\n+\t\t\t\treturn rc;\n+\t\t}\n+\n+\t\trc = inode_sid_has_perm(layer-\u003emounter_sid, inode, av, \u0026ad);\n+\t\tif (rc)\n+\t\t\treturn rc;\n+\t}\n+\n+\treturn 0;\n+}\n+\n static int __file_map_prot_check(const struct file file, unsigned long prot,\n \t\t\t\t bool shared, bool mounter_check,\n \t\t\t\t bool bf_user_file)\n@@ -4004,14 +4114,10 @@ static int __file_map_prot_check(const struct file file, unsigned long prot,\n \tif (file) {\n \t\tconst struct cred cred = mounter_check ?\n \t\t\t\tfile-\u003ef_cred : current_cred();\n-\t\t/* \"read\" always possible, \"write\" only if shared /\n-\t\tu32 av = FILE__READ;\n-\t\tif (shared \u0026\u0026 prot_write)\n-\t\t\tav \|= FILE__WRITE;\n-\t\tif (prot_exec)\n-\t\t\tav \|= FILE__EXECUTE;\n \n-\t\treturn __file_has_perm(cred, file, av, bf_user_file);\n+\t\treturn __file_has_perm(cred, file,\n+\t\t\t\t file_map_prot_to_av(prot, shared),\n+\t\t\t\t bf_user_file);\n \t}\n \n \treturn 0;\n@@ -4106,6 +4212,7 @@ static int selinux_file_mprotect(struct vm_area_struct vma,\n \tint rc;\n \tconst struct cred cred = current_cred();\n \tu32 sid = cred_sid(cred);\n+\tu32 av;\n \tconst struct file file = vma-\u003evm_file;\n \tbool backing_file;\n \tbool shared = vma-\u003evm_flags \u0026 VM_SHARED;\n@@ -4149,6 +4256,10 @@ static int selinux_file_mprotect(struct vm_area_struct vma,\n \t\t\tif (rc)\n \t\t\t\treturn rc;\n \t\t\tif (backing_file) {\n+\t\t\t\trc = backing_mounters_has_perm(file,\n+\t\t\t\t\t\t\t FILE__EXECMOD);\n+\t\t\t\tif (rc)\n+\t\t\t\t\treturn rc;\n \t\t\t\trc = file_has_perm(file-\u003ef_cred, file,\n \t\t\t\t\t\t FILE__EXECMOD);\n \t\t\t\tif (rc)\n@@ -4161,6 +4272,10 @@ static int selinux_file_mprotect(struct vm_area_struct vma,\n \tif (rc)\n \t\treturn rc;\n \tif (backing_file) {\n+\t\tav = file_map_prot_to_av(prot, shared);\n+\t\trc = backing_mounters_has_perm(file, av);\n+\t\tif (rc)\n+\t\t\treturn rc;\n \t\trc = file_map_prot_check(file, prot, shared, true);\n \t\tif (rc)\n \t\t\treturn rc;\n@@ -7635,6 +7750,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {\n \tLSM_HOOK_INIT(file_permission, selinux_file_permission),\n \tLSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security),\n \tLSM_HOOK_INIT(backing_file_alloc, selinux_backing_file_alloc),\n+\tLSM_HOOK_INIT(backing_file_free, selinux_backing_file_free),\n \tLSM_HOOK_INIT(file_ioctl, selinux_file_ioctl),\n \tLSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat),\n \tLSM_HOOK_INIT(mmap_file, selinux_mmap_file),\ndiff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h\nindex 3c0a16ec978b0..2f21568251ffe 100644\n--- a/security/selinux/include/objsec.h\n+++ b/security/selinux/include/objsec.h\n@@ -86,8 +86,16 @@ struct file_security_struct {\n \tu32 pseqno; /* Policy seqno at the time of file open /\n };\n \n+struct backing_file_security_layer {\n+\tstruct path path; / this layer's real path /\n+\tu32 mounter_sid; / SID of the mounter that opened it /\n+\tu32 fd_sid; / SID of its open file description /\n+};\n+\n struct backing_file_security_struct {\n-\tu32 uf_sid; / associated user file fsec-\u003esid /\n+\tu32 uf_sid; / top-level user file fsec-\u003esid /\n+\tu32 layer_count; / number of intermediate backing files /\n+\tstruct backing_file_security_layer layers;\n };\n \n struct superblock_security_struct {\n" }
2/1	2026/08/29 22:23	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "SECURITY", "SECURITY_SELINUX", "SECURITY_NETWORK", "AUDIT", "NET", "INET", "OVERLAY_FS" ], "FocusSymbols": [ "selinux_backing_file_alloc", "selinux_backing_file_free", "selinux_file_mprotect", "security_backing_file_alloc", "security_backing_file_free", "security_file_mprotect" ], "Reasoning": "The patch adds support for tracking and enforcing SELinux permissions across multi-layer backing files (such as those used by overlayfs and erofs). It implements dynamic allocation and reference tracking of intermediate backing file layers in selinux_backing_file_alloc, cleanup in selinux_backing_file_free, and multi-layer permission checks during mprotect in selinux_file_mprotect. These changes modify core security and filesystem interactions and are well worth fuzzing.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer. Your job is to review a provided patch series and determine if it makes functional changes to the kernel that should be fuzzed. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively use your code access tools to examine the actual source code and confirm any assumptions. Return WorthFuzzing=false if the patch only contains: - Modifications to Documentation/, Kconfig files, or code comments. - Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints. - Changes to numeric constants or macros that do not functionally alter execution flow. - Code paths that are impossible to reach in virtualized environments like GCE or QEMU, even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim). - Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU. - Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove) that are executed only during PCI hot-unplug or sysfs driver unbind operations. If it modifies reachable core kernel logic, drivers, or architectures, use your code search tools to verify the code can be executed, then return WorthFuzzing=true. When returning WorthFuzzing=true, you MUST ALSO: 1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols. Avoid listing generic hot-path functions to prevent skewed test distributions. Prefer non-static, non-inlined API entrypoint functions over internal static helper functions (which are inlined by the compiler and do not have distinct symbol addresses). 2. Identify any specific CONFIG_ options required to properly test this new/modified feature. Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions. Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed for Kbuild to compile the code statically into vmlinux. List them in the EnableConfigs output array, and DO NOT add a '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: For your convenience, here is the diff of the changes: commit fa7a0b550622c645d62cf9a36498a7cabd726cb6 Author: syz-cluster <triage@syzkaller.com> Date: Sat Aug 29 22:23:21 2026 +0000 syz-cluster: applied patch under review diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 035aaf113d1da..b6750edcc4783 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1674,26 +1674,32 @@ static int cred_has_capability(const struct cred cred, return rc; } -/ Check whether a task has a particular permission to an inode. - The 'adp' parameter is optional and allows other audit - data to be passed (e.g. the dentry). / -static int inode_has_perm(const struct cred cred, - struct inode inode, - u32 perms, - struct common_audit_data adp) +/* + * Check whether a SID has a particular permission to an inode. The 'adp' + * parameter is optional and allows other audit data to be passed (e.g. the + * dentry). + / +static int inode_sid_has_perm(u32 sid, struct inode inode, u32 perms, + struct common_audit_data adp) { struct inode_security_struct isec; - u32 sid; if (unlikely(IS_PRIVATE(inode))) return 0; - sid = cred_sid(cred); isec = selinux_inode(inode); return avc_has_perm(sid, isec->sid, isec->sclass, perms, adp); } +static int inode_has_perm(const struct cred cred, + struct inode inode, + u32 perms, + struct common_audit_data adp) +{ + return inode_sid_has_perm(cred_sid(cred), inode, perms, adp); +} + / Same as inode_has_perm, but pass explicit audit data containing the dentry to help the auditing code to more easily generate the pathname if needed. / @@ -3843,17 +3849,74 @@ static int selinux_file_alloc_security(struct file file) return 0; } +static inline u32 selinux_file_user_sid(const struct file file) +{ + if (unlikely(file->f_mode & FMODE_BACKING)) + return selinux_backing_file(file)->uf_sid; + return selinux_file(file)->sid; +} + static int selinux_backing_file_alloc(struct file backing_file, const struct file user_file) { struct backing_file_security_struct bfsec; + const struct backing_file_security_struct ubfsec; + struct backing_file_security_layer layer; + u32 i; bfsec = selinux_backing_file(backing_file); - bfsec->uf_sid = selinux_file(user_file)->sid; + bfsec->uf_sid = selinux_file_user_sid(user_file); + if (!(user_file->f_mode & FMODE_BACKING)) + return 0; + + ubfsec = selinux_backing_file(user_file); + /* a wrapped count would make kmalloc_array() return ZERO_SIZE_PTR / + if (unlikely(ubfsec->layer_count == U32_MAX)) + return -EOVERFLOW; + + / + * The final VMA only retains the lowest backing file, so record the + * whole chain here rather than in the mmap hook, where concurrent + * mappings would have to be serialized. Size it dynamically: erofs + * inode sharing adds a backing file without bumping s_stack_depth. + / + bfsec->layers = kmalloc_array(ubfsec->layer_count + 1, + sizeof(bfsec->layers), GFP_KERNEL); + if (!bfsec->layers) + return -ENOMEM; + + for (i = 0; i < ubfsec->layer_count; i++) { + layer = &bfsec->layers[i]; + layer = ubfsec->layers[i]; + path_get(&layer->path); + } + + / f_path, not file_user_path(): this layer, not the top-level file / + layer = &bfsec->layers[i]; + layer->path = user_file->f_path; + layer->mounter_sid = cred_sid(user_file->f_cred); + layer->fd_sid = selinux_file(user_file)->sid; + path_get(&layer->path); + bfsec->layer_count = ubfsec->layer_count + 1; return 0; } +static void selinux_backing_file_free(struct file backing_file) +{ + struct backing_file_security_struct bfsec; + + / security_backing_file_free() may be called twice after an error / + if (!backing_file_security(backing_file)) + return; + + bfsec = selinux_backing_file(backing_file); + while (bfsec->layer_count) + path_put(&bfsec->layers[--bfsec->layer_count].path); + kfree(bfsec->layers); + bfsec->layers = NULL; +} + / * Check whether a task has the ioctl permission and cmd * operation to an inode. @@ -3971,6 +4034,53 @@ static int selinux_file_ioctl_compat(struct file file, unsigned int cmd, static int default_noexec __ro_after_init; +static u32 file_map_prot_to_av(unsigned long prot, bool shared) +{ + u32 av = FILE__READ; + + if (shared && (prot & PROT_WRITE)) + av \|= FILE__WRITE; + if (prot & PROT_EXEC) + av \|= FILE__EXECUTE; + + return av; +} + +static int backing_mounters_has_perm(const struct file file, u32 av) +{ + const struct backing_file_security_struct bfsec; + const struct backing_file_security_layer layer; + struct common_audit_data ad; + struct inode inode; + u32 i; + int rc; + + if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) + return -EIO; + + bfsec = selinux_backing_file(file); + for (i = 0; i < bfsec->layer_count; i++) { + layer = &bfsec->layers[i]; + inode = d_inode(layer->path.dentry); + + ad.type = LSM_AUDIT_DATA_PATH; + ad.u.path = layer->path; + + if (layer->mounter_sid != layer->fd_sid) { + rc = avc_has_perm(layer->mounter_sid, layer->fd_sid, + SECCLASS_FD, FD__USE, &ad); + if (rc) + return rc; + } + + rc = inode_sid_has_perm(layer->mounter_sid, inode, av, &ad); + if (rc) + return rc; + } + + return 0; +} + static int __file_map_prot_check(const struct file file, unsigned long prot, bool shared, bool mounter_check, bool bf_user_file) @@ -4004,14 +4114,10 @@ static int __file_map_prot_check(const struct file file, unsigned long prot, if (file) { const struct cred cred = mounter_check ? file->f_cred : current_cred(); - /* "read" always possible, "write" only if shared / - u32 av = FILE__READ; - if (shared && prot_write) - av \|= FILE__WRITE; - if (prot_exec) - av \|= FILE__EXECUTE; - return __file_has_perm(cred, file, av, bf_user_file); + return __file_has_perm(cred, file, + file_map_prot_to_av(prot, shared), + bf_user_file); } return 0; @@ -4106,6 +4212,7 @@ static int selinux_file_mprotect(struct vm_area_struct vma, int rc; const struct cred cred = current_cred(); u32 sid = cred_sid(cred); + u32 av; const struct file file = vma->vm_file; bool backing_file; bool shared = vma->vm_flags & VM_SHARED; @@ -4149,6 +4256,10 @@ static int selinux_file_mprotect(struct vm_area_struct vma, if (rc) return rc; if (backing_file) { + rc = backing_mounters_has_perm(file, + FILE__EXECMOD); + if (rc) + return rc; rc = file_has_perm(file->f_cred, file, FILE__EXECMOD); if (rc) @@ -4161,6 +4272,10 @@ static int selinux_file_mprotect(struct vm_area_struct vma, if (rc) return rc; if (backing_file) { + av = file_map_prot_to_av(prot, shared); + rc = backing_mounters_has_perm(file, av); + if (rc) + return rc; rc = file_map_prot_check(file, prot, shared, true); if (rc) return rc; @@ -7635,6 +7750,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(backing_file_alloc, selinux_backing_file_alloc), + LSM_HOOK_INIT(backing_file_free, selinux_backing_file_free), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl), LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h index 3c0a16ec978b0..2f21568251ffe 100644 --- a/security/selinux/include/objsec.h +++ b/security/selinux/include/objsec.h @@ -86,8 +86,16 @@ struct file_security_struct { u32 pseqno; /* Policy seqno at the time of file open / }; +struct backing_file_security_layer { + struct path path; / this layer's real path / + u32 mounter_sid; / SID of the mounter that opened it / + u32 fd_sid; / SID of its open file description / +}; + struct backing_file_security_struct { - u32 uf_sid; / associated user file fsec->sid / + u32 uf_sid; / top-level user file fsec->sid / + u32 layer_count; / number of intermediate backing files / + struct backing_file_security_layer layers; }; struct superblock_security_struct {
3/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 5030 output: 30 thoughts: 233 Thoughts: Analyzing This Patch for Fuzzing Potential Okay, let's dive into this. My initial assessment is: is this patch fuzzable? What configurations are essential to reproduce the bug? And what key functions and data structures should I target as focus symbols for reporting? Alright, let's take a look at the code changes. Ah, it's touching `security/selinux/hooks.c` and `security/selinux/include/objsec.h`. Interesting. It seems like we're updating how SELinux interacts with backing files, things like overlayfs, stacked filesystems, and erofs. So, specifically, the changes are centered around these functions: `inode_sid_has_perm`, `inode_has_perm`, `selinux_file_user_sid`, `selinux_backing_file_alloc`, `selinux_backing_file_free`, `file_map_prot_to_av`, `backing_mounters_has_perm`, `selinux_file_mprotect` and also the SELinux hooks array: a new registration of `backing_file_free`. Now, before I start constructing a fuzzer or even thinking about config options, I need to get a really solid grasp on the surrounding code. I need to understand the relationship between these backing file functions, the SELinux implementation, and how the hooks are used. Time to fire up grepper or just carefully read through the file to fully understand the logic and how these pieces fit together.
4/2	2026/08/29 22:23	tool	grepper	0m Args: { "Expression": "SECURITY_SELINUX", "PathPrefix": "security/selinux" } Results: { "Output": "security/selinux/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nsecurity/selinux/Kconfig:2:config SECURITY_SELINUX\nsecurity/selinux/Kconfig-3-\tbool \"SELinux Support\"\n--\nsecurity/selinux/Kconfig-11-\nsecurity/selinux/Kconfig:12:config SECURITY_SELINUX_BOOTPARAM\nsecurity/selinux/Kconfig-13-\tbool \"SELinux boot parameter\"\nsecurity/selinux/Kconfig:14:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-15-\tdefault n\n--\nsecurity/selinux/Kconfig-25-\nsecurity/selinux/Kconfig:26:config SECURITY_SELINUX_DEVELOP\nsecurity/selinux/Kconfig-27-\tbool \"SELinux Development Support\"\nsecurity/selinux/Kconfig:28:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-29-\tdefault y\n--\nsecurity/selinux/Kconfig-39-\nsecurity/selinux/Kconfig:40:config SECURITY_SELINUX_AVC_STATS\nsecurity/selinux/Kconfig-41-\tbool \"SELinux AVC Statistics\"\nsecurity/selinux/Kconfig:42:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-43-\tdefault y\n--\nsecurity/selinux/Kconfig-48-\nsecurity/selinux/Kconfig:49:config SECURITY_SELINUX_SIDTAB_HASH_BITS\nsecurity/selinux/Kconfig-50-\tint \"SELinux sidtab hashtable size\"\nsecurity/selinux/Kconfig:51:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-52-\trange 8 13\n--\nsecurity/selinux/Kconfig-55-\t This option sets the number of buckets used in the sidtab hashtable\nsecurity/selinux/Kconfig:56:\t to 2^SECURITY_SELINUX_SIDTAB_HASH_BITS buckets. The number of hash\nsecurity/selinux/Kconfig-57-\t collisions may be viewed at /sys/fs/selinux/ss/sidtab_hash_stats. If\n--\nsecurity/selinux/Kconfig-60-\nsecurity/selinux/Kconfig:61:config SECURITY_SELINUX_SID2STR_CACHE_SIZE\nsecurity/selinux/Kconfig-62-\tint \"SELinux SID to context string translation cache size\"\nsecurity/selinux/Kconfig:63:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-64-\tdefault 256\n--\nsecurity/selinux/Kconfig-71-\nsecurity/selinux/Kconfig:72:config SECURITY_SELINUX_AVC_HASH_BITS\nsecurity/selinux/Kconfig-73-\tint \"SELinux avc hashtable size\"\nsecurity/selinux/Kconfig:74:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-75-\trange 9 14\n--\nsecurity/selinux/Kconfig-78-\t This option sets the number of buckets used in the AVC hash table\nsecurity/selinux/Kconfig:79:\t to 2^SECURITY_SELINUX_AVC_HASH_BITS. A higher value helps maintain\nsecurity/selinux/Kconfig-80-\t shorter chain lengths especially when expanding AVC nodes via\n--\nsecurity/selinux/Kconfig-82-\nsecurity/selinux/Kconfig:83:config SECURITY_SELINUX_DEBUG\nsecurity/selinux/Kconfig-84-\tbool \"SELinux kernel debugging support\"\nsecurity/selinux/Kconfig:85:\tdepends on SECURITY_SELINUX\nsecurity/selinux/Kconfig-86-\tdefault n\n--\nsecurity/selinux/Makefile-10-\nsecurity/selinux/Makefile:11:obj-$(CONFIG_SECURITY_SELINUX) := selinux.o\nsecurity/selinux/Makefile-12-\nsecurity/selinux/Makefile=13=ccflags-y := -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include\nsecurity/selinux/Makefile-14-\nsecurity/selinux/Makefile:15:ccflags-$(CONFIG_SECURITY_SELINUX_DEBUG) += -DDEBUG\nsecurity/selinux/Makefile-16-\n--\nsecurity/selinux/avc.c-37-\nsecurity/selinux/avc.c:38:#define AVC_CACHE_SLOTS\t\t(1 \u003c\u003c CONFIG_SECURITY_SELINUX_AVC_HASH_BITS)\nsecurity/selinux/avc.c-39-#define AVC_DEF_CACHE_THRESHOLD\tAVC_CACHE_SLOTS\n--\nsecurity/selinux/avc.c-41-\nsecurity/selinux/avc.c:42:#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS\nsecurity/selinux/avc.c-43-#define avc_cache_stats_incr(field)\tthis_cpu_inc(avc_cache_stats.field)\n--\nsecurity/selinux/avc.c=80=struct avc_callback_node {\n--\nsecurity/selinux/avc.c-85-\nsecurity/selinux/avc.c:86:#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS\nsecurity/selinux/avc.c-87-DEFINE_PER_CPU(struct avc_cache_stats, avc_cache_stats) = { 0 };\n--\nsecurity/selinux/hooks.c=117=static atomic_t selinux_secmark_refcount = ATOMIC_INIT(0);\nsecurity/selinux/hooks.c-118-\nsecurity/selinux/hooks.c:119:#ifdef CONFIG_SECURITY_SELINUX_DEVELOP\nsecurity/selinux/hooks.c-120-static int selinux_enforcing_boot __initdata;\n--\nsecurity/selinux/hooks.c=134=int selinux_enabled_boot __initdata = 1;\nsecurity/selinux/hooks.c:135:#ifdef CONFIG_SECURITY_SELINUX_BOOTPARAM\nsecurity/selinux/hooks.c-136-static int __init selinux_enabled_setup(char str)\n--\nsecurity/selinux/include/avc.h=166=void avc_set_cache_threshold(unsigned int cache_threshold);\nsecurity/selinux/include/avc.h-167-\nsecurity/selinux/include/avc.h:168:#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS\nsecurity/selinux/include/avc.h-169-DECLARE_PER_CPU(struct avc_cache_stats, avc_cache_stats);\n--\nsecurity/selinux/include/security.h=94=struct selinux_state {\nsecurity/selinux/include/security.h:95:#ifdef CONFIG_SECURITY_SELINUX_DEVELOP\nsecurity/selinux/include/security.h-96-\tbool enforcing;\n--\nsecurity/selinux/include/security.h=118=static inline void selinux_mark_initialized(void)\n--\nsecurity/selinux/include/security.h-123-\nsecurity/selinux/include/security.h:124:#ifdef CONFIG_SECURITY_SELINUX_DEVELOP\nsecurity/selinux/include/security.h-125-static inline bool enforcing_enabled(void)\n--\nsecurity/selinux/selinuxfs.c=120=static ssize_t sel_read_enforce(struct file filp, char __user buf,\n--\nsecurity/selinux/selinuxfs.c-130-\nsecurity/selinux/selinuxfs.c:131:#ifdef CONFIG_SECURITY_SELINUX_DEVELOP\nsecurity/selinux/selinuxfs.c-132-static ssize_t sel_write_enforce(struct file file, const char __user buf,\n--\nsecurity/selinux/selinuxfs.c=1392=static const struct file_operations sel_avc_hash_stats_ops = {\n--\nsecurity/selinux/selinuxfs.c-1396-\nsecurity/selinux/selinuxfs.c:1397:#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS\nsecurity/selinux/selinuxfs.c-1398-static struct avc_cache_stats sel_avc_get_stat_idx(loff_t idx)\n--\nsecurity/selinux/selinuxfs.c=1468=static int sel_make_avc_files(struct dentry dir)\n--\nsecurity/selinux/selinuxfs.c-1477-\t\t{ \"hash_stats\", \u0026sel_avc_hash_stats_ops, S_IRUGO },\nsecurity/selinux/selinuxfs.c:1478:#ifdef CONFIG_SECURITY_SELINUX_AVC_STATS\nsecurity/selinux/selinuxfs.c-1479-\t\t{ \"cache_stats\", \u0026sel_avc_cache_stats_ops, S_IRUGO },\n--\nsecurity/selinux/ss/avtab.c=253=int avtab_alloc_dup(struct avtab new, const struct avtab orig)\n--\nsecurity/selinux/ss/avtab.c-257-\nsecurity/selinux/ss/avtab.c:258:#ifdef CONFIG_SECURITY_SELINUX_DEBUG\nsecurity/selinux/ss/avtab.c-259-void avtab_hash_eval(struct avtab h, const char tag)\n--\nsecurity/selinux/ss/avtab.c-289-}\nsecurity/selinux/ss/avtab.c:290:#endif /* CONFIG_SECURITY_SELINUX_DEBUG /\nsecurity/selinux/ss/avtab.c-291-\n--\nsecurity/selinux/ss/avtab.h=107=void avtab_destroy(struct avtab h);\n--\nsecurity/selinux/ss/avtab.h-111-\nsecurity/selinux/ss/avtab.h:112:#ifdef CONFIG_SECURITY_SELINUX_DEBUG\nsecurity/selinux/ss/avtab.h-113-void avtab_hash_eval(struct avtab h, const char tag);\n--\nsecurity/selinux/ss/hashtab.c=88=int hashtab_map(struct hashtab h, int (apply)(void k, void d, void args),\n--\nsecurity/selinux/ss/hashtab.c-106-\nsecurity/selinux/ss/hashtab.c:107:#ifdef CONFIG_SECURITY_SELINUX_DEBUG\nsecurity/selinux/ss/hashtab.c-108-void hashtab_stat(struct hashtab h, struct hashtab_info info)\n--\nsecurity/selinux/ss/hashtab.c-137-}\nsecurity/selinux/ss/hashtab.c:138:#endif / CONFIG_SECURITY_SELINUX_DEBUG /\nsecurity/selinux/ss/hashtab.c-139-\n--\nsecurity/selinux/ss/hashtab.h=139=int hashtab_duplicate(struct hashtab new, const struct hashtab orig,\n--\nsecurity/selinux/ss/hashtab.h-143-\nsecurity/selinux/ss/hashtab.h:144:#ifdef CONFIG_SECURITY_SELINUX_DEBUG\nsecurity/selinux/ss/hashtab.h-145-/ Fill info with some hash table statistics /\n--\nsecurity/selinux/ss/policydb.c-40-\nsecurity/selinux/ss/policydb.c:41:#ifdef CONFIG_SECURITY_SELINUX_DEBUG\nsecurity/selinux/ss/policydb.c-42-/ clang-format off /\n--\nsecurity/selinux/ss/policydb.c=691=static int (const index_f[SYM_NUM])(void key, void datum, void datap) = {\n--\nsecurity/selinux/ss/policydb.c-702-\nsecurity/selinux/ss/policydb.c:703:#ifdef CONFIG_SECURITY_SELINUX_DEBUG\nsecurity/selinux/ss/policydb.c-704-static void hash_eval(struct hashtab h, const char hash_name,\n--\nsecurity/selinux/ss/policydb.c=730=static inline void symtab_hash_eval(struct symtab s)\n--\nsecurity/selinux/ss/policydb.c-732-}\nsecurity/selinux/ss/policydb.c:733:#endif /* CONFIG_SECURITY_SELINUX_DEBUG /\nsecurity/selinux/ss/policydb.c-734-\n--\nsecurity/selinux/ss/sidtab.c=35=int sidtab_init(struct sidtab s)\n--\nsecurity/selinux/ss/sidtab.c-50-\nsecurity/selinux/ss/sidtab.c:51:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.c:52:\ts-\u003ecache_free_slots = CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE;\nsecurity/selinux/ss/sidtab.c-53-\tINIT_LIST_HEAD(\u0026s-\u003ecache_lru_list);\n--\nsecurity/selinux/ss/sidtab.c=78=int sidtab_set_initial(struct sidtab s, u32 sid, struct context context)\n--\nsecurity/selinux/ss/sidtab.c-92-\nsecurity/selinux/ss/sidtab.c:93:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.c-94-\tisid-\u003eentry.cache = NULL;\n--\nsecurity/selinux/ss/sidtab.c=508=static void sidtab_destroy_entry(struct sidtab_entry entry)\n--\nsecurity/selinux/ss/sidtab.c-510-\tcontext_destroy(\u0026entry-\u003econtext);\nsecurity/selinux/ss/sidtab.c:511:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.c-512-\tkfree(rcu_dereference_raw(entry-\u003ecache));\n--\nsecurity/selinux/ss/sidtab.c=541=void sidtab_destroy(struct sidtab s)\n--\nsecurity/selinux/ss/sidtab.c-560-\nsecurity/selinux/ss/sidtab.c:561:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.c-562-\n--\nsecurity/selinux/ss/sidtab.c=608=int sidtab_sid2str_get(struct sidtab s, struct sidtab_entry entry, char *out,\n--\nsecurity/selinux/ss/sidtab.c-637-\nsecurity/selinux/ss/sidtab.c:638:#endif / CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0 /\n--\nsecurity/selinux/ss/sidtab.h=21=struct sidtab_entry {\n--\nsecurity/selinux/ss/sidtab.h-24-\tstruct context context;\nsecurity/selinux/ss/sidtab.h:25:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.h-26-\tstruct sidtab_str_cache __rcu cache;\n--\nsecurity/selinux/ss/sidtab.h=69=struct sidtab_convert_params {\n--\nsecurity/selinux/ss/sidtab.h-73-\nsecurity/selinux/ss/sidtab.h:74:#define SIDTAB_HASH_BITS CONFIG_SECURITY_SELINUX_SIDTAB_HASH_BITS\nsecurity/selinux/ss/sidtab.h-75-#define SIDTAB_HASH_BUCKETS (1 \u003c\u003c SIDTAB_HASH_BITS)\n--\nsecurity/selinux/ss/sidtab.h=77=struct sidtab {\n--\nsecurity/selinux/ss/sidtab.h-92-\nsecurity/selinux/ss/sidtab.h:93:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.h-94-\t/* SID -\u003e context string cache /\n--\nsecurity/selinux/ss/sidtab.h=139=int sidtab_hash_stats(struct sidtab sidtab, char page);\nsecurity/selinux/ss/sidtab.h-140-\nsecurity/selinux/ss/sidtab.h:141:#if CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0\nsecurity/selinux/ss/sidtab.h-142-void sidtab_sid2str_put(struct sidtab s, struct sidtab_entry entry,\n--\nsecurity/selinux/ss/sidtab.h=152=static inline int sidtab_sid2str_get(struct sidtab s,\n--\nsecurity/selinux/ss/sidtab.h-157-}\nsecurity/selinux/ss/sidtab.h:158:#endif /* CONFIG_SECURITY_SELINUX_SID2STR_CACHE_SIZE \u003e 0 /\nsecurity/selinux/ss/sidtab.h-159-\n--\nsecurity/selinux/xfrm.c-24- \tCONFIG_SECURITY_NETWORK_XFRM=y\nsecurity/selinux/xfrm.c:25: \tCONFIG_SECURITY_SELINUX=m/y\nsecurity/selinux/xfrm.c-26- ISSUES:\n" }
5/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 10209 output: 31 thoughts: 42 Thoughts: Okay, let's dive into this. I need to figure out how SELinux is configured within this kernel build. My initial instinct is to go straight to the Kconfig files, the core configuration mechanisms. Specifically, I'm thinking I'll start with the general `security/Kconfig` file. That's where I'd expect to find the top-level options related to security features. SELinux Configuration Investigation Alright, first things first, I'm going to check those `Kconfig` files. I'll need to look in both the top-level `security/Kconfig` and then also the more specific `security/selinux/Kconfig` to see how SELinux is set up. They might be separate files for more clarity, or they might be one and the same file. In any case, I know I'll find the relevant options there. Let's see what we can find. I'll start with `security/Kconfig`, that's usually the best place to start.
6/2	2026/08/29 22:23	tool	read-file	0m Args: { "File": "security/Kconfig", "FirstLine": 1, "LineCount": 100 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\t#\n 3:\t# Security configuration\n 4:\t#\n 5:\t\n 6:\tmenu \"Security options\"\n 7:\t\n 8:\tsource \"security/keys/Kconfig\"\n 9:\t\n 10:\tconfig SECURITY_DMESG_RESTRICT\n 11:\t\tbool \"Restrict unprivileged access to the kernel syslog\"\n 12:\t\tdefault n\n 13:\t\thelp\n 14:\t\t This enforces restrictions on unprivileged users reading the kernel\n 15:\t\t syslog via dmesg(8).\n 16:\t\n 17:\t\t If this option is not selected, no restrictions will be enforced\n 18:\t\t unless the dmesg_restrict sysctl is explicitly set to (1).\n 19:\t\n 20:\t\t If you are unsure how to answer this question, answer N.\n 21:\t\n 22:\tchoice\n 23:\t\tprompt \"Allow /proc/pid/mem access override\"\n 24:\t\tdefault PROC_MEM_FORCE_PTRACE\n 25:\t\thelp\n 26:\t\t Traditionally /proc/pid/mem allows users to override memory\n 27:\t\t permissions for users like ptrace, assuming they have ptrace\n 28:\t\t capability.\n 29:\t\n 30:\t\t This allows people to limit that - either never override, or\n 31:\t\t require actual active ptrace attachment (default).\n 32:\t\n 33:\tconfig PROC_MEM_ALWAYS_FORCE\n 34:\t\tbool \"Traditional /proc/pid/mem behavior\"\n 35:\t\thelp\n 36:\t\t This allows /proc/pid/mem accesses to override memory mapping\n 37:\t\t permissions if you have ptrace access rights.\n 38:\t\n 39:\tconfig PROC_MEM_FORCE_PTRACE\n 40:\t\tbool \"Require active ptrace() use for access override\"\n 41:\t\thelp\n 42:\t\t This allows /proc/pid/mem accesses to override memory mapping\n 43:\t\t permissions for active ptracers like gdb.\n 44:\t\n 45:\tconfig PROC_MEM_NO_FORCE\n 46:\t\tbool \"Never\"\n 47:\t\thelp\n 48:\t\t Never override memory mapping permissions\n 49:\t\n 50:\tendchoice\n 51:\t\n 52:\tconfig MSEAL_SYSTEM_MAPPINGS\n 53:\t\tbool \"mseal system mappings\"\n 54:\t\tdepends on 64BIT\n 55:\t\tdepends on ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS\n 56:\t\tdepends on !CHECKPOINT_RESTORE\n 57:\t\thelp\n 58:\t\t Apply mseal on system mappings.\n 59:\t\t The system mappings includes vdso, vvar, vvar_vclock,\n 60:\t\t vectors (arm compat-mode), sigpage (arm compat-mode), uprobes.\n 61:\t\n 62:\t\t A 64-bit kernel is required for the memory sealing feature.\n 63:\t\t No specific hardware features from the CPU are needed.\n 64:\t\n 65:\t\t WARNING: This feature breaks programs which rely on relocating\n 66:\t\t or unmapping system mappings. Known broken software at the time\n 67:\t\t of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore\n 68:\t\t this config can't be enabled universally.\n 69:\t\n 70:\t\t For complete descriptions of memory sealing, please see\n 71:\t\t Documentation/userspace-api/mseal.rst\n 72:\t\n 73:\tconfig SECURITY\n 74:\t\tbool \"Enable different security models\"\n 75:\t\tdepends on SYSFS\n 76:\t\tdepends on MULTIUSER\n 77:\t\thelp\n 78:\t\t This allows you to choose different security modules to be\n 79:\t\t configured into your kernel.\n 80:\t\n 81:\t\t If this option is not selected, the default Linux security\n 82:\t\t model will be used.\n 83:\t\n 84:\t\t If you are unsure how to answer this question, answer N.\n 85:\t\n 86:\tconfig HAS_SECURITY_AUDIT\n 87:\t\tdef_bool y\n 88:\t\tdepends on AUDIT\n 89:\t\tdepends on SECURITY\n 90:\t\n 91:\tconfig SECURITYFS\n 92:\t\tbool \"Enable the securityfs filesystem\"\n 93:\t\thelp\n 94:\t\t This will build the securityfs filesystem. It is currently used by\n 95:\t\t various security modules (AppArmor, IMA, SafeSetID, TOMOYO, TPM).\n 96:\t\n 97:\t\t If you are unsure how to answer this question, answer N.\n 98:\t\n 99:\tconfig SECURITY_NETWORK\n 100:\t\tbool \"Socket and Networking Security Hooks\"\n" }
7/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 11765 output: 34 thoughts: 14 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Diving into the SELinux Kconfig Alright, time to get to the heart of the matter. I need to take a look at the `security/selinux/Kconfig` file. Given my familiarity with the SELinux ecosystem and kernel configuration, this should be a fairly straightforward process. I expect to find the core options for enabling, disabling, and configuring SELinux within the kernel, along with the dependencies and relationships to other security modules. I'll be particularly interested in: * Overall Enablement: The top-level `CONFIG_SECURITY_SELINUX` option, naturally. I need to quickly assess how it's defined and if there are any conditional dependencies. * Policy Control: I'll be looking for configuration options that control aspects of the default policy and policy loading. This might include options for enforcing or permissive modes, and whether it has dynamic loading capabilities. * Advanced Features: Depending on the kernel version and configuration, I'll scan for any advanced features defined, such as MLS/MCS support or other specialized SELinux capabilities that may need to be enabled or disabled. * Interactions: I'll also glance at the surrounding configuration space to ensure compatibility, especially with other security modules (e.g., IMA, LSMs). The relationships are always interesting. Essentially, I'm setting the stage. This initial examination of `Kconfig` will provide a foundational understanding of how SELinux is integrated into this specific kernel configuration. It'll direct my attention to other aspects I might need to consider, or to other related files that need attention. Once I have a good grasp of the configuration options, I can move on to the actual implementation and assess its impact.
8/2	2026/08/29 22:23	tool	read-file	0m Args: { "File": "security/selinux/Kconfig", "FirstLine": 1, "LineCount": 40 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\tconfig SECURITY_SELINUX\n 3:\t\tbool \"SELinux Support\"\n 4:\t\tdepends on SECURITY_NETWORK \u0026\u0026 AUDIT \u0026\u0026 NET \u0026\u0026 INET\n 5:\t\tselect NETWORK_SECMARK\n 6:\t\tdefault n\n 7:\t\thelp\n 8:\t\t This selects Security-Enhanced Linux (SELinux).\n 9:\t\t You will also need a policy configuration and a labeled filesystem.\n 10:\t\t If you are unsure how to answer this question, answer N.\n 11:\t\n 12:\tconfig SECURITY_SELINUX_BOOTPARAM\n 13:\t\tbool \"SELinux boot parameter\"\n 14:\t\tdepends on SECURITY_SELINUX\n 15:\t\tdefault n\n 16:\t\thelp\n 17:\t\t This option adds a kernel parameter 'selinux', which allows SELinux\n 18:\t\t to be disabled at boot. If this option is selected, SELinux\n 19:\t\t functionality can be disabled with selinux=0 on the kernel\n 20:\t\t command line. The purpose of this option is to allow a single\n 21:\t\t kernel image to be distributed with SELinux built in, but not\n 22:\t\t necessarily enabled.\n 23:\t\n 24:\t\t If you are unsure how to answer this question, answer N.\n 25:\t\n 26:\tconfig SECURITY_SELINUX_DEVELOP\n 27:\t\tbool \"SELinux Development Support\"\n 28:\t\tdepends on SECURITY_SELINUX\n 29:\t\tdefault y\n 30:\t\thelp\n 31:\t\t This enables the development support option of SELinux,\n 32:\t\t which is useful for experimenting with SELinux and developing\n 33:\t\t policies. If unsure, say Y. With this option enabled, the\n 34:\t\t kernel will start in permissive mode (log everything, deny nothing)\n 35:\t\t unless you specify enforcing=1 on the kernel command line. You\n 36:\t\t can interactively toggle the kernel between enforcing mode and\n 37:\t\t permissive mode (if permitted by the policy) via\n 38:\t\t /sys/fs/selinux/enforce.\n 39:\t\n 40:\tconfig SECURITY_SELINUX_AVC_STATS\n" }
9/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 12791 output: 28 thoughts: 254 Thoughts: Analyzing SELinux File Protection Hook Modifications Okay, let's dive into the changes made within `security/selinux/hooks.c`. I need to understand the implications of these modifications, so I'll go through the diff carefully. It looks like we have a set of core functions that have been tweaked. First, I see several helper functions have been modified: `inode_sid_has_perm`, `inode_has_perm`, `selinux_file_user_sid`, `file_map_prot_to_av`, `backing_mounters_has_perm`, and `__file_map_prot_check`. These are the internal building blocks and any modification here potentially has wide impacts. Crucially, I also see two LSM hooks being modified: `selinux_backing_file_alloc` and `selinux_backing_file_free`, as well as `selinux_file_mprotect`. This is where the SELinux policy enforcement is integrated into the kernel's file protection mechanisms. I need to understand how these hooks are defined and called within the LSM framework itself and how SELinux is using them. Therefore, my next step is to examine `security/security.c`. I'll be looking for the corresponding definitions and usage of the `security_file_mprotect`, `security_backing_file_alloc`, and `security_backing_file_free` functions. This will clarify how the SELinux hooks I observed in `hooks.c` are actually wired into the broader security framework. It’s important to understand the full context of these modifications, and how they relate to the underlying LSM implementation.
10/2	2026/08/29 22:23	tool	grepper	0m Args: { "Expression": "security_backing_file_", "PathPrefix": "security/" } Results: { "Output": "security/security.c=2433=void security_file_free(struct file file)\n--\nsecurity/security.c-2446-/\nsecurity/security.c:2447: security_backing_file_alloc() - Allocate and setup a backing file blob\nsecurity/security.c-2448- * @backing_file: the backing file\n--\nsecurity/security.c-2462- /\nsecurity/security.c:2463:int security_backing_file_alloc(struct file backing_file,\nsecurity/security.c-2464-\t\t\t\tconst struct file user_file)\n--\nsecurity/security.c-2472-\tif (unlikely(rc))\nsecurity/security.c:2473:\t\tsecurity_backing_file_free(backing_file);\nsecurity/security.c-2474-\n--\nsecurity/security.c-2478-/\nsecurity/security.c:2479: security_backing_file_free() - Free a backing file blob\nsecurity/security.c-2480- * @backing_file: the backing file\n--\nsecurity/security.c-2484- /\nsecurity/security.c:2485:void security_backing_file_free(struct file backing_file)\nsecurity/security.c-2486-{\n--\nsecurity/selinux/hooks.c=3905=static void selinux_backing_file_free(struct file backing_file)\n--\nsecurity/selinux/hooks.c-3908-\nsecurity/selinux/hooks.c:3909:\t/ security_backing_file_free() may be called twice after an error */\nsecurity/selinux/hooks.c-3910-\tif (!backing_file_security(backing_file))\n" }
11/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 13889 output: 20 thoughts: 57 Thoughts: Here's my analysis of those function names, expressed as your request: Analyzing Security Backing File Operations Okay, so I'm looking at these function names: `security_backing_file_alloc`, `security_backing_file_free`, and `security_file_mprotect`. Immediately, I see a clear relationship. They all deal with, as the names suggest, security-related interactions with backing files, which likely relates to file-backed memory regions and their security contexts. Given my experience, I'm assuming we are dealing with some form of memory protection tied to file mapping or possibly sandboxing. My next step is clear: I need to understand the call graph. I'm going to determine which functions are calling `security_backing_file_alloc` and `security_backing_file_free`. Tracing these calls will give me valuable context. Understanding the code paths that use the allocation and freeing functions will reveal the specific security concerns and the overall operational patterns surrounding the backing file security mechanism. This will likely show the initialization and destruction process for security contexts associated with the backing file.
12/2	2026/08/29 22:23	tool	grepper	0m Args: { "Expression": "security_backing_file_" } Results: { "Output": "fs/file_table.c=88=static inline void backing_file_free(struct backing_file ff)\nfs/file_table.c-89-{\nfs/file_table.c:90:\tsecurity_backing_file_free(\u0026ff-\u003efile);\nfs/file_table.c-91-\tpath_put(\u0026ff-\u003euser_path);\n--\nfs/file_table.c=311=static int init_backing_file(struct backing_file ff,\n--\nfs/file_table.c-315-\tbacking_file_set_security(\u0026ff-\u003efile, NULL);\nfs/file_table.c:316:\treturn security_backing_file_alloc(\u0026ff-\u003efile, user_file);\nfs/file_table.c-317-}\n--\ninclude/linux/security.h=474=void security_file_free(struct file file);\ninclude/linux/security.h:475:int security_backing_file_alloc(struct file backing_file,\ninclude/linux/security.h-476-\t\t\t\tconst struct file user_file);\ninclude/linux/security.h:477:void security_backing_file_free(struct file backing_file);\ninclude/linux/security.h-478-int security_file_ioctl(struct file file, unsigned int cmd, unsigned long arg);\n--\ninclude/linux/security.h=1148=static inline void security_file_free(struct file file)\n--\ninclude/linux/security.h-1150-\ninclude/linux/security.h:1151:static inline int security_backing_file_alloc(struct file backing_file,\ninclude/linux/security.h-1152-\t\t\t\t\t const struct file user_file)\n--\ninclude/linux/security.h-1156-\ninclude/linux/security.h:1157:static inline void security_backing_file_free(struct file backing_file)\ninclude/linux/security.h-1158-{ }\n--\nsecurity/security.c=2433=void security_file_free(struct file file)\n--\nsecurity/security.c-2446-/*\nsecurity/security.c:2447: security_backing_file_alloc() - Allocate and setup a backing file blob\nsecurity/security.c-2448- * @backing_file: the backing file\n--\nsecurity/security.c-2462- /\nsecurity/security.c:2463:int security_backing_file_alloc(struct file backing_file,\nsecurity/security.c-2464-\t\t\t\tconst struct file user_file)\n--\nsecurity/security.c-2472-\tif (unlikely(rc))\nsecurity/security.c:2473:\t\tsecurity_backing_file_free(backing_file);\nsecurity/security.c-2474-\n--\nsecurity/security.c-2478-/\nsecurity/security.c:2479: security_backing_file_free() - Free a backing file blob\nsecurity/security.c-2480- * @backing_file: the backing file\n--\nsecurity/security.c-2484- /\nsecurity/security.c:2485:void security_backing_file_free(struct file backing_file)\nsecurity/security.c-2486-{\n--\nsecurity/selinux/hooks.c=3905=static void selinux_backing_file_free(struct file backing_file)\n--\nsecurity/selinux/hooks.c-3908-\nsecurity/selinux/hooks.c:3909:\t/ security_backing_file_free() may be called twice after an error */\nsecurity/selinux/hooks.c-3910-\tif (!backing_file_security(backing_file))\n" }
13/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 15161 output: 20 thoughts: 118 Thoughts: Analyzing Backing File Security Okay, let's break this down. My focus right now is on the security implications of backing files, especially within something like overlayfs. I see that `backing_file_alloc` and `backing_file_free` are the key entry points; they're the hooks when backing files are opened and released, handling the lifecycle, perhaps via `backing_file_open_ptr` or `backing_tmpfile_open`. Crucially, when `mprotect` is called on a memory mapping that involves a backing file, `selinux_file_mprotect` is triggered. That tells me I need to dig into the call paths of `security_file_mprotect` itself. Where else is this security check happening? I need to understand how widely these protections are implemented to properly assess the overall security of the system.
14/2	2026/08/29 22:23	tool	grepper	0m Args: { "Expression": "security_file_mprotect" } Results: { "Output": "include/linux/security.h=486=int security_mmap_addr(unsigned long addr);\ninclude/linux/security.h:487:int security_file_mprotect(struct vm_area_struct vma, unsigned long reqprot,\ninclude/linux/security.h-488-\t\t\t unsigned long prot);\n--\ninclude/linux/security.h=1186=static inline int security_mmap_addr(unsigned long addr)\n--\ninclude/linux/security.h-1190-\ninclude/linux/security.h:1191:static inline int security_file_mprotect(struct vm_area_struct vma,\ninclude/linux/security.h-1192-\t\t\t\t\t unsigned long reqprot,\n--\nmm/mprotect.c=871=static int do_mprotect_pkey(unsigned long start, size_t len,\n--\nmm/mprotect.c-987-\nmm/mprotect.c:988:\t\terror = security_file_mprotect(vma, reqprot, prot);\nmm/mprotect.c-989-\t\tif (error)\n--\nsecurity/security.c=2619=int security_mmap_addr(unsigned long addr)\n--\nsecurity/security.c-2624-/*\nsecurity/security.c:2625: security_file_mprotect() - Check if changing memory protections is allowed\nsecurity/security.c-2626- * @vma: memory region\n--\nsecurity/security.c-2633- /\nsecurity/security.c:2634:int security_file_mprotect(struct vm_area_struct vma, unsigned long reqprot,\nsecurity/security.c-2635-\t\t\t unsigned long prot)\n" }
15/2	2026/08/29 22:23	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 15922 output: 34 thoughts: 909 Thoughts: Fuzzing Target Identification: SELinux Backing File Handling Okay, so this patch introduces support for multi-layer backing files within SELinux permissions checks, specifically during `mprotect` operations. It's handling the allocation, deallocation, and tracking of `backing_file_security` structures, including those pesky layers. Looking at the code, it's touching dynamic memory allocation (crucial!), path reference counting, and permission checks on backing files, the usual suspects, right? OverlayFS, EROFS stacks, nested OverlayFS – the works. The key functions are `selinux_backing_file_alloc`, `selinux_backing_file_free`, and `selinux_file_mprotect`. These all look interesting for fuzzing: `selinux_backing_file_alloc` allocates an array, copies existing layers, and appends the current one, getting path references. Then, `selinux_backing_file_free` frees the paths and the array itself. Finally, `selinux_file_mprotect` calls `backing_mounters_has_perm`, which is crucial for determining mounter permissions. Is this reachable and worth the effort? Absolutely! This is core SELinux logic, handling file and mprotect permission checks, and reference tracking on backing files. It's fully reachable in virtualized environments like QEMU, making it a prime target. Now, let's nail down the `FocusSymbols`. According to the instructions, we want specific kernel functions, ideally non-static entry points, to avoid skewing the fuzz test distribution. Forget generic hot-path functions. So, let's dive into the patch's functions. I see `selinux_backing_file_alloc`, `selinux_backing_file_free`, and `selinux_file_mprotect` in `security/selinux/hooks.c`, but they're marked static. However, they're registered in the `selinux_hooks` table as `backing_file_alloc`, `backing_file_free`, and `file_mprotect` respectively. There are also `security_backing_file_alloc`, `security_backing_file_free`, and `security_file_mprotect` in `security/security.c`, but I have a feeling the static-declared ones are the ones we want. Since their addresses are taken in the `selinux_hooks` table, the compiler can't completely inline them. I'm pretty sure they retain their symbols in vmlinux. That's good. And the `security_backing_file_alloc`, `security_backing_file_free`, `security_file_mprotect` in `security/security.c` are the non-static entry points. So, it's: * `selinux_backing_file_alloc` (registered as `backing_file_alloc`) * `selinux_backing_file_free` (registered as `backing_file_free`) * `selinux_file_mprotect` (registered as `file_mprotect`) * `security_backing_file_alloc` * `security_backing_file_free` * `security_file_mprotect` We'll add both sets.
16/2	2026/08/29 22:24	tool	read-file	0m Args: { "File": "security/security.c", "FirstLine": 2445, "LineCount": 50 } Results: { "Contents": "2445:\t\n2446:\t/*\n2447:\t security_backing_file_alloc() - Allocate and setup a backing file blob\n2448:\t * @backing_file: the backing file\n2449:\t * @user_file: the associated user visible file\n2450:\t \n2451:\t Allocate a backing file LSM blob and perform any necessary initialization of\n2452:\t * the LSM blob. There will be some operations where the LSM will not have\n2453:\t * access to @user_file after this point, so any important state associated\n2454:\t * with @user_file that is important to the LSM should be captured in the\n2455:\t * backing file's LSM blob.\n2456:\t \n2457:\t LSM's should avoid taking a reference to @user_file in this hook as it will\n2458:\t * result in problems later when the system attempts to drop/put the file\n2459:\t * references due to a circular dependency.\n2460:\t \n2461:\t Return: Return 0 if the hook is successful, negative values otherwise.\n2462:\t /\n2463:\tint security_backing_file_alloc(struct file backing_file,\n2464:\t\t\t\t\tconst struct file user_file)\n2465:\t{\n2466:\t\tint rc;\n2467:\t\n2468:\t\trc = lsm_backing_file_alloc(backing_file);\n2469:\t\tif (rc)\n2470:\t\t\treturn rc;\n2471:\t\trc = call_int_hook(backing_file_alloc, backing_file, user_file);\n2472:\t\tif (unlikely(rc))\n2473:\t\t\tsecurity_backing_file_free(backing_file);\n2474:\t\n2475:\t\treturn rc;\n2476:\t}\n2477:\t\n2478:\t/\n2479:\t security_backing_file_free() - Free a backing file blob\n2480:\t * @backing_file: the backing file\n2481:\t \n2482:\t Free any LSM state associate with a backing file's LSM blob, including the\n2483:\t * blob itself.\n2484:\t /\n2485:\tvoid security_backing_file_free(struct file backing_file)\n2486:\t{\n2487:\t\tvoid *blob = backing_file_security(backing_file);\n2488:\t\n2489:\t\tcall_void_hook(backing_file_free, backing_file);\n2490:\t\n2491:\t\tif (blob) {\n2492:\t\t\tbacking_file_set_security(backing_file, NULL);\n2493:\t\t\tkmem_cache_free(lsm_backing_file_cache, blob);\n2494:\t\t}\n" }
17/2	2026/08/29 22:24	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 18349 output: 34 thoughts: 20 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into the `security_file_mprotect` Function Okay, so we need to understand what's happening around `security_file_mprotect` in `security/security.c`. That's where the file protection magic happens, so it's a critical area for examining potential security vulnerabilities or control flow. I'm going to pull up the code and start tracing the calls, looking for any obvious holes or areas that might be exploitable. Specifically, I'll be looking at how file access permissions are handled in conjunction with memory protection changes. Are there race conditions? Are there insufficient checks on user input? Are there ways to bypass the intended security restrictions through clever manipulation of the system calls? I'll pay close attention to the context in which `security_file_mprotect` is being invoked, including what other security modules or hooks are active at the time. I'll need to look at any interaction with LSMs, because that's always an important detail. Let's see what we've got.
18/2	2026/08/29 22:24	tool	read-file	0m Args: { "File": "security/security.c", "FirstLine": 2625, "LineCount": 25 } Results: { "Contents": "2625:\t * security_file_mprotect() - Check if changing memory protections is allowed\n2626:\t * @vma: memory region\n2627:\t * @reqprot: application requested protection\n2628:\t * @prot: protection applied by the kernel\n2629:\t \n2630:\t Check permissions before changing memory access permissions.\n2631:\t \n2632:\t Return: Returns 0 if permission is granted.\n2633:\t /\n2634:\tint security_file_mprotect(struct vm_area_struct vma, unsigned long reqprot,\n2635:\t\t\t\t unsigned long prot)\n2636:\t{\n2637:\t\treturn call_int_hook(file_mprotect, vma, reqprot, prot);\n2638:\t}\n2639:\t\n2640:\t/*\n2641:\t security_file_lock() - Check if a file lock is allowed\n2642:\t * @file: file\n2643:\t * @cmd: lock operation (e.g. F_RDLCK, F_WRLCK)\n2644:\t \n2645:\t Check permission before performing file locking operations. Note the hook\n2646:\t * mediates both flock and fcntl style locks.\n2647:\t \n2648:\t Return: Returns 0 if permission is granted.\n2649:\t */\n" }
19/2	2026/08/29 22:24	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 19021 output: 27 thoughts: 297 Thoughts: My Kconfig Configuration Deep Dive Okay, let's break this down from a configuration perspective. I need to nail down the SELinux requirements first. Jumping into `security/selinux/Kconfig`, I see `SECURITY_SELINUX` is the key. It's a boolean, dependent on `SECURITY_NETWORK`, `AUDIT`, `NET`, and `INET`, and it `select`s `NETWORK_SECMARK`, with a default of 'n'. Looks straightforward enough. Now, let's double-check the dependencies. `SECURITY_NETWORK` relies on both `SECURITY` and `NET`, which makes sense. I know `AUDIT` lives in `init/Kconfig`, and `INET` is just `CONFIG_INET`. Excellent, I've got the core SELinux dependencies clearly mapped. But that's probably not the whole story. I should explore other potentially related configurations, not just the obvious. The commit message mentions `OVERLAY_FS` and `EROFS_FS`, so let's dig into those specifically. The mention of backing files, `s_stack_depth`, and inode sharing indicates a potential interaction. Let's start with `OVERLAY_FS` in `fs/overlayfs/Kconfig`.
20/2	2026/08/29 22:24	tool	grepper	0m Args: { "Expression": "config OVERLAY_FS", "PathPrefix": "fs/" } Results: { "Output": "fs/overlayfs/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/overlayfs/Kconfig:2:config OVERLAY_FS\nfs/overlayfs/Kconfig-3-\ttristate \"Overlay filesystem support\"\n--\nfs/overlayfs/Kconfig-14-\nfs/overlayfs/Kconfig:15:config OVERLAY_FS_REDIRECT_DIR\nfs/overlayfs/Kconfig-16-\tbool \"Overlayfs: turn on redirect directory feature by default\"\n--\nfs/overlayfs/Kconfig-30-\nfs/overlayfs/Kconfig:31:config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW\nfs/overlayfs/Kconfig-32-\tbool \"Overlayfs: follow redirects even if redirects are turned off\"\n--\nfs/overlayfs/Kconfig-45-\nfs/overlayfs/Kconfig:46:config OVERLAY_FS_INDEX\nfs/overlayfs/Kconfig-47-\tbool \"Overlayfs: turn on inodes index feature by default\"\n--\nfs/overlayfs/Kconfig-64-\nfs/overlayfs/Kconfig:65:config OVERLAY_FS_NFS_EXPORT\nfs/overlayfs/Kconfig-66-\tbool \"Overlayfs: turn on NFS export feature by default\"\n--\nfs/overlayfs/Kconfig-92-\nfs/overlayfs/Kconfig:93:config OVERLAY_FS_XINO_AUTO\nfs/overlayfs/Kconfig-94-\tbool \"Overlayfs: auto enable inode number mapping\"\n--\nfs/overlayfs/Kconfig-110-\nfs/overlayfs/Kconfig:111:config OVERLAY_FS_METACOPY\nfs/overlayfs/Kconfig-112-\tbool \"Overlayfs: turn on metadata only copy up feature by default\"\n--\nfs/overlayfs/Kconfig-128-\nfs/overlayfs/Kconfig:129:config OVERLAY_FS_DEBUG\nfs/overlayfs/Kconfig-130-\tbool \"Overlayfs: turn on extra debugging checks\"\n" }
21/2	2026/08/29 22:24	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 20119 output: 19 thoughts: 39 Thoughts: Okay, here's my take on those thoughts, framed from my expert perspective: Investigating Potential Backing File Usage in Filesystems Right, let's dive in. My immediate thought is, I need to figure out if `OVERLAY_FS` or any related filesystems are employing backing files in their implementation. That's a crucial aspect for understanding their behavior, especially when it comes to performance, data persistence, and how they interact with the underlying storage. To do that, I'll go directly to the source code. My preferred approach? A targeted grep. I'll search for specific function names within the kernel sources that are highly suggestive of backing file operations. I'll focus on `backing_file_open` and `init_backing_file`. Those are the two functions that would typically be involved when a filesystem needs to deal with a backing file to support operations, so I know those would give me useful results. I'm expecting this will quickly lead me to the key locations in the code that I need to examine more closely to see precisely how backing files are used. Once I find those instances I can get to the bottom of the issue much quicker.
22/2	2026/08/29 22:24	tool	grepper	0m Args: { "Expression": "backing_file_open" } Results: { "Output": "fs/backing-file.c-19-/*\nfs/backing-file.c:20: backing_file_open - open a backing file for kernel internal use\nfs/backing-file.c-21- * @user_file: file the user requested to open\n--\nfs/backing-file.c-33- /\nfs/backing-file.c:34:struct file backing_file_open(const struct file user_file, int flags,\nfs/backing-file.c-35-\t\t\t const struct path real_path,\n--\nfs/backing-file.c-55-}\nfs/backing-file.c:56:EXPORT_SYMBOL_GPL(backing_file_open);\nfs/backing-file.c-57-\n--\nfs/erofs/ishare.c=96=static int erofs_ishare_file_open(struct inode inode, struct file file)\n--\nfs/erofs/ishare.c-106-\nfs/erofs/ishare.c:107:\trf = backing_file_open(file, file-\u003ef_flags \| O_NOATIME,\nfs/erofs/ishare.c-108-\t\t\t \u0026sharedpath, current_cred());\n--\nfs/fuse/passthrough.c=152=struct fuse_backing fuse_passthrough_open(struct file file, int backing_id)\n--\nfs/fuse/passthrough.c-169-\t/* Allocate backing file per fuse file to store fuse path /\nfs/fuse/passthrough.c:170:\tbacking_file = backing_file_open(file, file-\u003ef_flags,\nfs/fuse/passthrough.c-171-\t\t\t\t\t \u0026fb-\u003efile-\u003ef_path, fb-\u003ecred);\n--\nfs/overlayfs/file.c=28=static struct file ovl_open_realfile(const struct file file,\n--\nfs/overlayfs/file.c-50-\nfs/overlayfs/file.c:51:\t\t\trealfile = backing_file_open(file,\nfs/overlayfs/file.c-52-\t\t\t\t\t\t flags, realpath, current_cred());\n--\ninclude/linux/backing-file.h=15=struct backing_file_ctx {\n--\ninclude/linux/backing-file.h-20-\ninclude/linux/backing-file.h:21:struct file backing_file_open(const struct file user_file, int flags,\ninclude/linux/backing-file.h-22-\t\t\t const struct path real_path,\n" }
23/2	2026/08/29 22:24	llm	patch-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 21060 output: 230 thoughts: 484 Thoughts: My Analysis of the SELinux Backing File Patch Okay, let's break this down. First, I'm noting the callers of `backing_file_open`: `overlayfs`, `erofs`, and `fuse`. That's important context. This patch appears related to handling security implications when these filesystems use backing files, particularly in a multi-layered context. And as expected, enabling SELinux requires a specific set of configs: `SECURITY_SELINUX`, `SECURITY`, `AUDIT`, `NET`, `INET`, and `SECURITY_NETWORK`. The presence of `CONFIG_OVERLAY_FS` is critical to really see the behavior being addressed. Now, let's quickly review those SELinux symbols that are the focus here: `selinux_backing_file_alloc`, `selinux_backing_file_free`, `selinux_file_mprotect`, `security_backing_file_alloc`, `security_backing_file_free`, and `security_file_mprotect`. Good, these are the hooks and wrappers. That confirms that we are dealing with entrypoints that have been altered in the code. I don't see anything generic here, these are security-specific hooks or wrappers that make sense within the SELinux subsystem. So, the config dependencies are the expected: `SECURITY_SELINUX`, `SECURITY`, `SECURITY_NETWORK`, `AUDIT`, `NET`, `INET`, and `OVERLAY_FS`. No surprises there. My reasoning is straightforward: this patch is about enhancing SELinux to correctly handle and validate permissions when dealing with multi-layered backing files. It's really tackling the issue of how stacked filesystems (like `overlayfs` and `erofs` when they share inodes) interact with SELinux permissions during `mprotect` and backing file allocation/deallocation. Specifically, it seems like the implementation includes dynamic layer allocation, path reference counting in `selinux_backing_file_alloc`, cleaning up properly in `selinux_backing_file_free`, and validating permissions for intermediate mounters in `selinux_file_mprotect`. These changes directly influence security permission checks and backing file memory management.
24/2	2026/08/29 22:24	tool	set-results	0m Args: { "EnableConfigs": [ "SECURITY", "SECURITY_SELINUX", "SECURITY_NETWORK", "AUDIT", "NET", "INET", "OVERLAY_FS" ], "FocusSymbols": [ "selinux_backing_file_alloc", "selinux_backing_file_free", "selinux_file_mprotect", "security_backing_file_alloc", "security_backing_file_free", "security_file_mprotect" ], "Reasoning": "The patch adds support for tracking and enforcing SELinux permissions across multi-layer backing files (such as those used by overlayfs and erofs). It implements dynamic allocation and reference tracking of intermediate backing file layers in selinux_backing_file_alloc, cleanup in selinux_backing_file_free, and multi-layer permission checks during mprotect in selinux_file_mprotect. These changes modify core security and filesystem interactions and are well worth fuzzing.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "SECURITY", "SECURITY_SELINUX", "SECURITY_NETWORK", "AUDIT", "NET", "INET", "OVERLAY_FS" ], "FocusSymbols": [ "selinux_backing_file_alloc", "selinux_backing_file_free", "selinux_file_mprotect", "security_backing_file_alloc", "security_backing_file_free", "security_file_mprotect" ], "Reasoning": "The patch adds support for tracking and enforcing SELinux permissions across multi-layer backing files (such as those used by overlayfs and erofs). It implements dynamic allocation and reference tracking of intermediate backing file layers in selinux_backing_file_alloc, cleanup in selinux_backing_file_free, and multi-layer permission checks during mprotect in selinux_file_mprotect. These changes modify core security and filesystem interactions and are well worth fuzzing.", "WorthFuzzing": true }
25/1	2026/08/29 22:24	action	If	0m Args: { "WorthFuzzing": true } Results: null
26/2	2026/08/29 22:24	agent	kmsan-evaluator	0m Model: core Args: null Results: { "KMSANReasoning": "The patch extends SELinux backing file tracking to handle multiple layers in stacked filesystems (such as overlayfs and erofs) by introducing intermediate backing layer structures, recording paths and SIDs, and validating mounter permissions during file mmap/mprotect operations.\n\nAll newly allocated heap structures (`backing_file_security_layer` arrays) are explicitly and fully initialized upon allocation before use or copying. The containing `backing_file_security_struct` blob is allocated via `kmem_cache_zalloc`. The audit data stack structure `struct common_audit_data ad` is properly configured with `type = LSM_AUDIT_DATA_PATH` and the path union member assigned before passing to the audit/AVC subsystem. No data is exposed or copied to user space, and there is no branching on uninitialized memory. Potential risks in this patch (such as lifetime issues, refcounting, path management, or out-of-bounds indexing) fall within the scope of KASAN rather than KMSAN.", "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: For your convenience, here is the diff of the changes: commit fa7a0b550622c645d62cf9a36498a7cabd726cb6 Author: syz-cluster <triage@syzkaller.com> Date: Sat Aug 29 22:23:21 2026 +0000 syz-cluster: applied patch under review diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 035aaf113d1da..b6750edcc4783 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1674,26 +1674,32 @@ static int cred_has_capability(const struct cred cred, return rc; } -/ Check whether a task has a particular permission to an inode. - The 'adp' parameter is optional and allows other audit - data to be passed (e.g. the dentry). / -static int inode_has_perm(const struct cred cred, - struct inode inode, - u32 perms, - struct common_audit_data adp) +/* + * Check whether a SID has a particular permission to an inode. The 'adp' + * parameter is optional and allows other audit data to be passed (e.g. the + * dentry). + / +static int inode_sid_has_perm(u32 sid, struct inode inode, u32 perms, + struct common_audit_data adp) { struct inode_security_struct isec; - u32 sid; if (unlikely(IS_PRIVATE(inode))) return 0; - sid = cred_sid(cred); isec = selinux_inode(inode); return avc_has_perm(sid, isec->sid, isec->sclass, perms, adp); } +static int inode_has_perm(const struct cred cred, + struct inode inode, + u32 perms, + struct common_audit_data adp) +{ + return inode_sid_has_perm(cred_sid(cred), inode, perms, adp); +} + / Same as inode_has_perm, but pass explicit audit data containing the dentry to help the auditing code to more easily generate the pathname if needed. / @@ -3843,17 +3849,74 @@ static int selinux_file_alloc_security(struct file file) return 0; } +static inline u32 selinux_file_user_sid(const struct file file) +{ + if (unlikely(file->f_mode & FMODE_BACKING)) + return selinux_backing_file(file)->uf_sid; + return selinux_file(file)->sid; +} + static int selinux_backing_file_alloc(struct file backing_file, const struct file user_file) { struct backing_file_security_struct bfsec; + const struct backing_file_security_struct ubfsec; + struct backing_file_security_layer layer; + u32 i; bfsec = selinux_backing_file(backing_file); - bfsec->uf_sid = selinux_file(user_file)->sid; + bfsec->uf_sid = selinux_file_user_sid(user_file); + if (!(user_file->f_mode & FMODE_BACKING)) + return 0; + + ubfsec = selinux_backing_file(user_file); + /* a wrapped count would make kmalloc_array() return ZERO_SIZE_PTR / + if (unlikely(ubfsec->layer_count == U32_MAX)) + return -EOVERFLOW; + + / + * The final VMA only retains the lowest backing file, so record the + * whole chain here rather than in the mmap hook, where concurrent + * mappings would have to be serialized. Size it dynamically: erofs + * inode sharing adds a backing file without bumping s_stack_depth. + / + bfsec->layers = kmalloc_array(ubfsec->layer_count + 1, + sizeof(bfsec->layers), GFP_KERNEL); + if (!bfsec->layers) + return -ENOMEM; + + for (i = 0; i < ubfsec->layer_count; i++) { + layer = &bfsec->layers[i]; + layer = ubfsec->layers[i]; + path_get(&layer->path); + } + + / f_path, not file_user_path(): this layer, not the top-level file / + layer = &bfsec->layers[i]; + layer->path = user_file->f_path; + layer->mounter_sid = cred_sid(user_file->f_cred); + layer->fd_sid = selinux_file(user_file)->sid; + path_get(&layer->path); + bfsec->layer_count = ubfsec->layer_count + 1; return 0; } +static void selinux_backing_file_free(struct file backing_file) +{ + struct backing_file_security_struct bfsec; + + / security_backing_file_free() may be called twice after an error / + if (!backing_file_security(backing_file)) + return; + + bfsec = selinux_backing_file(backing_file); + while (bfsec->layer_count) + path_put(&bfsec->layers[--bfsec->layer_count].path); + kfree(bfsec->layers); + bfsec->layers = NULL; +} + / * Check whether a task has the ioctl permission and cmd * operation to an inode. @@ -3971,6 +4034,53 @@ static int selinux_file_ioctl_compat(struct file file, unsigned int cmd, static int default_noexec __ro_after_init; +static u32 file_map_prot_to_av(unsigned long prot, bool shared) +{ + u32 av = FILE__READ; + + if (shared && (prot & PROT_WRITE)) + av \|= FILE__WRITE; + if (prot & PROT_EXEC) + av \|= FILE__EXECUTE; + + return av; +} + +static int backing_mounters_has_perm(const struct file file, u32 av) +{ + const struct backing_file_security_struct bfsec; + const struct backing_file_security_layer layer; + struct common_audit_data ad; + struct inode inode; + u32 i; + int rc; + + if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) + return -EIO; + + bfsec = selinux_backing_file(file); + for (i = 0; i < bfsec->layer_count; i++) { + layer = &bfsec->layers[i]; + inode = d_inode(layer->path.dentry); + + ad.type = LSM_AUDIT_DATA_PATH; + ad.u.path = layer->path; + + if (layer->mounter_sid != layer->fd_sid) { + rc = avc_has_perm(layer->mounter_sid, layer->fd_sid, + SECCLASS_FD, FD__USE, &ad); + if (rc) + return rc; + } + + rc = inode_sid_has_perm(layer->mounter_sid, inode, av, &ad); + if (rc) + return rc; + } + + return 0; +} + static int __file_map_prot_check(const struct file file, unsigned long prot, bool shared, bool mounter_check, bool bf_user_file) @@ -4004,14 +4114,10 @@ static int __file_map_prot_check(const struct file file, unsigned long prot, if (file) { const struct cred cred = mounter_check ? file->f_cred : current_cred(); - /* "read" always possible, "write" only if shared / - u32 av = FILE__READ; - if (shared && prot_write) - av \|= FILE__WRITE; - if (prot_exec) - av \|= FILE__EXECUTE; - return __file_has_perm(cred, file, av, bf_user_file); + return __file_has_perm(cred, file, + file_map_prot_to_av(prot, shared), + bf_user_file); } return 0; @@ -4106,6 +4212,7 @@ static int selinux_file_mprotect(struct vm_area_struct vma, int rc; const struct cred cred = current_cred(); u32 sid = cred_sid(cred); + u32 av; const struct file file = vma->vm_file; bool backing_file; bool shared = vma->vm_flags & VM_SHARED; @@ -4149,6 +4256,10 @@ static int selinux_file_mprotect(struct vm_area_struct vma, if (rc) return rc; if (backing_file) { + rc = backing_mounters_has_perm(file, + FILE__EXECMOD); + if (rc) + return rc; rc = file_has_perm(file->f_cred, file, FILE__EXECMOD); if (rc) @@ -4161,6 +4272,10 @@ static int selinux_file_mprotect(struct vm_area_struct vma, if (rc) return rc; if (backing_file) { + av = file_map_prot_to_av(prot, shared); + rc = backing_mounters_has_perm(file, av); + if (rc) + return rc; rc = file_map_prot_check(file, prot, shared, true); if (rc) return rc; @@ -7635,6 +7750,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(backing_file_alloc, selinux_backing_file_alloc), + LSM_HOOK_INIT(backing_file_free, selinux_backing_file_free), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl), LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h index 3c0a16ec978b0..2f21568251ffe 100644 --- a/security/selinux/include/objsec.h +++ b/security/selinux/include/objsec.h @@ -86,8 +86,16 @@ struct file_security_struct { u32 pseqno; /* Policy seqno at the time of file open / }; +struct backing_file_security_layer { + struct path path; / this layer's real path / + u32 mounter_sid; / SID of the mounter that opened it / + u32 fd_sid; / SID of its open file description / +}; + struct backing_file_security_struct { - u32 uf_sid; / associated user file fsec->sid / + u32 uf_sid; / top-level user file fsec->sid / + u32 layer_count; / number of intermediate backing files / + struct backing_file_security_layer layers; }; struct superblock_security_struct {
27/3	2026/08/29 22:24	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 5027 output: 26 thoughts: 748 Thoughts: Analyzing the SELinux Backing File Patch Okay, let's dive into this patch and figure out if we need to fire up a KMSAN session. My initial thought is to understand the changes first. This patch touches `security/selinux/hooks.c` and `security/selinux/include/objsec.h`, so it seems core to how SELinux handles object security. The key seems to be about tracking intermediate backing files for stacked filesystems like overlayfs or erofs. The code adds a `struct backing_file_security_layer`, with `struct path path; u32 mounter_sid; u32 fd_sid;`, which sounds like it's designed to keep track of security information at each layer of the filesystem stack. Then, the `struct backing_file_security_struct` is extended with a `layer_count` and an array `layers` of these `backing_file_security_layer` structs. Now, the allocation is where things get interesting. I see a `kmalloc_array` being used to allocate the `layers` array within `selinux_backing_file_alloc`. Hold on, a slight flag: `kmalloc_array` and not `kcalloc` – that's a red flag. Let me see how it's initialized. Looking at the code: ```c bfsec->layers = kmalloc_array(ubfsec->layer_count + 1, sizeof(bfsec->layers), GFP_KERNEL); if (!bfsec->layers) return -ENOMEM; for (i = 0; i < ubfsec->layer_count; i++) { layer = &bfsec->layers[i]; layer = ubfsec->layers[i]; path_get(&layer->path); } /* f_path, not file_user_path(): this layer, not the top-level file / layer = &bfsec->layers[i]; layer->path = user_file->f_path; layer->mounter_sid = cred_sid(user_file->f_cred); layer->fd_sid = selinux_file(user_file)->sid; path_get(&layer->path); bfsec->layer_count = ubfsec->layer_count + 1; ``` Okay, I see now. `ubfsec->layer_count` elements are copied from `ubfsec->layers` into `bfsec->layers` (indexes 0 to `ubfsec->layer_count - 1`). Then, the code explicitly* initializes the element at index `ubfsec->layer_count` (which is equal to `i`) with values for `path`, `mounter_sid`, and `fd_sid`. `layer_count` is then set to `ubfsec->layer_count + 1`. So, every element from index `0` up to `layer_count - 1` gets properly initialized, given the loop. That's good. However, the comment `f_path, not file_user_path(): this layer, not the top-level file` needs further scrutiny regarding what this implies regarding overall file handling. Okay, let's consider the case when `!(user_file->f_mode & FMODE_BACKING)`. What happens then? The code simply sets `bfsec->uf_sid` to `selinux_file_user_sid(user_file)` and returns. In this case, I need to understand how `bfsec` itself gets allocated in that scenario. So, I need to track the allocation of `backing_file_security` or `selinux_backing_file` to see the full picture. I need to trace this allocation.
28/3	2026/08/29 22:25	tool	grepper	0m Args: { "Expression": "backing_file.security", "PathPrefix": "security" } Results:* { "Output": "security/security.c=185=static int lsm_backing_file_alloc(struct file backing_file)\n--\nsecurity/security.c-189-\tif (!lsm_backing_file_cache) {\nsecurity/security.c:190:\t\tbacking_file_set_security(backing_file, NULL);\nsecurity/security.c-191-\t\treturn 0;\n--\nsecurity/security.c-194-\tblob = kmem_cache_zalloc(lsm_backing_file_cache, GFP_KERNEL);\nsecurity/security.c:195:\tbacking_file_set_security(backing_file, blob);\nsecurity/security.c-196-\tif (!blob)\n--\nsecurity/security.c=2485=void security_backing_file_free(struct file backing_file)\nsecurity/security.c-2486-{\nsecurity/security.c:2487:\tvoid blob = backing_file_security(backing_file);\nsecurity/security.c-2488-\n--\nsecurity/security.c-2491-\tif (blob) {\nsecurity/security.c:2492:\t\tbacking_file_set_security(backing_file, NULL);\nsecurity/security.c-2493-\t\tkmem_cache_free(lsm_backing_file_cache, blob);\n--\nsecurity/selinux/hooks.c=1757=static int __file_has_perm(const struct cred cred, const struct file file,\n--\nsecurity/selinux/hooks.c-1767-\tif (bf_user_file) {\nsecurity/selinux/hooks.c:1768:\t\tstruct backing_file_security_struct bfsec;\nsecurity/selinux/hooks.c-1769-\t\tconst struct path path;\n--\nsecurity/selinux/hooks.c=3859=static int selinux_backing_file_alloc(struct file backing_file,\n--\nsecurity/selinux/hooks.c-3861-{\nsecurity/selinux/hooks.c:3862:\tstruct backing_file_security_struct bfsec;\nsecurity/selinux/hooks.c:3863:\tconst struct backing_file_security_struct ubfsec;\nsecurity/selinux/hooks.c:3864:\tstruct backing_file_security_layer layer;\nsecurity/selinux/hooks.c-3865-\tu32 i;\n--\nsecurity/selinux/hooks.c=3905=static void selinux_backing_file_free(struct file backing_file)\nsecurity/selinux/hooks.c-3906-{\nsecurity/selinux/hooks.c:3907:\tstruct backing_file_security_struct bfsec;\nsecurity/selinux/hooks.c-3908-\nsecurity/selinux/hooks.c-3909-\t/ security_backing_file_free() may be called twice after an error /\nsecurity/selinux/hooks.c:3910:\tif (!backing_file_security(backing_file))\nsecurity/selinux/hooks.c-3911-\t\treturn;\n--\nsecurity/selinux/hooks.c=4049=static int backing_mounters_has_perm(const struct file file, u32 av)\nsecurity/selinux/hooks.c-4050-{\nsecurity/selinux/hooks.c:4051:\tconst struct backing_file_security_struct bfsec;\nsecurity/selinux/hooks.c:4052:\tconst struct backing_file_security_layer layer;\nsecurity/selinux/hooks.c-4053-\tstruct common_audit_data ad;\n--\nsecurity/selinux/hooks.c=7642=struct lsm_blob_sizes selinux_blob_sizes __ro_after_init = {\n--\nsecurity/selinux/hooks.c-7645-\t.lbs_file = sizeof(struct file_security_struct),\nsecurity/selinux/hooks.c:7646:\t.lbs_backing_file = sizeof(struct backing_file_security_struct),\nsecurity/selinux/hooks.c-7647-\t.lbs_inode = sizeof(struct inode_security_struct),\n--\nsecurity/selinux/include/objsec.h=82=struct file_security_struct {\n--\nsecurity/selinux/include/objsec.h-88-\nsecurity/selinux/include/objsec.h:89:struct backing_file_security_layer {\nsecurity/selinux/include/objsec.h-90-\tstruct path path; /* this layer's real path /\n--\nsecurity/selinux/include/objsec.h-94-\nsecurity/selinux/include/objsec.h:95:struct backing_file_security_struct {\nsecurity/selinux/include/objsec.h-96-\tu32 uf_sid; / top-level user file fsec-\u003esid /\nsecurity/selinux/include/objsec.h-97-\tu32 layer_count; / number of intermediate backing files /\nsecurity/selinux/include/objsec.h:98:\tstruct backing_file_security_layer layers;\nsecurity/selinux/include/objsec.h-99-};\n--\nsecurity/selinux/include/objsec.h=203=static inline struct file_security_struct selinux_file(const struct file file)\n--\nsecurity/selinux/include/objsec.h-207-\nsecurity/selinux/include/objsec.h:208:static inline struct backing_file_security_struct \nsecurity/selinux/include/objsec.h-209-selinux_backing_file(const struct file backing_file)\nsecurity/selinux/include/objsec.h-210-{\nsecurity/selinux/include/objsec.h:211:\tvoid *blob = backing_file_security(backing_file);\nsecurity/selinux/include/objsec.h-212-\treturn blob + selinux_blob_sizes.lbs_backing_file;\n" }
29/3	2026/08/29 22:25	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 8206 output: 29 thoughts: 616 Thoughts: Analyzing Security Contexts in a Kernel Patch Okay, let's dive into this code. I'm focusing on the `security/security.c` file, specifically the `lsm_backing_file_alloc` function. The key here is the allocation of `blob` using `kmem_cache_zalloc`. Because it's zero-allocated, the `bfsec` structure is initialized with all zeros. This means that, upon allocation in this context, `layer_count` will be zero and `layers` will be `NULL`. This is significant because, if the `user_file` does not have the `FMODE_BACKING` flag set, we will maintain that zero state. Now, let's move to the stack variables in the patch. I'm especially interested in the `backing_mounters_has_perm` function. Looking at it, I need to understand how the `struct common_audit_data ad` is being used within the loop. The code iterates through backing file layers and checks permissions. It utilizes both `avc_has_perm` and `inode_sid_has_perm`, which appear to take `ad` as a parameter. It seems the code is using the path data in `ad`, and if those paths don't make sense, then there could be problems. My concern is how `ad` is initialized and used within those `avc_has_perm` and `inode_sid_has_perm` calls. I need to be absolutely certain of the typical initialization and usage of `common_audit_data` within the SELinux hooks. I need to understand how `ad` is populated and if there are any potential vulnerabilities or unexpected behavior that could arise from the way the paths are being passed in here. I'll need to go through the related selinux hook calls to make sure these arguments can't be misused.
30/3	2026/08/29 22:25	tool	grepper	0m Args: { "Expression": "ad\\.type =", "PathPrefix": "security/selinux" } Results: { "Output": "security/selinux/hooks.c=1643=static int cred_has_capability(const struct cred cred,\n--\nsecurity/selinux/hooks.c-1652-\nsecurity/selinux/hooks.c:1653:\tad.type = LSM_AUDIT_DATA_CAP;\nsecurity/selinux/hooks.c-1654-\tad.u.cap = cap;\n--\nsecurity/selinux/hooks.c=1706=static inline int dentry_has_perm(const struct cred cred,\n--\nsecurity/selinux/hooks.c-1713-\nsecurity/selinux/hooks.c:1714:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-1715-\tad.u.dentry = dentry;\n--\nsecurity/selinux/hooks.c=1725=static inline int path_has_perm(const struct cred cred,\n--\nsecurity/selinux/hooks.c-1732-\nsecurity/selinux/hooks.c:1733:\tad.type = LSM_AUDIT_DATA_PATH;\nsecurity/selinux/hooks.c-1734-\tad.u.path = path;\n--\nsecurity/selinux/hooks.c=1742=static inline int file_path_has_perm(const struct cred cred,\n--\nsecurity/selinux/hooks.c-1747-\nsecurity/selinux/hooks.c:1748:\tad.type = LSM_AUDIT_DATA_FILE;\nsecurity/selinux/hooks.c-1749-\tad.u.file = file;\n--\nsecurity/selinux/hooks.c=1757=static int __file_has_perm(const struct cred cred, const struct file file,\n--\nsecurity/selinux/hooks.c-1778-\nsecurity/selinux/hooks.c:1779:\t\tad.type = LSM_AUDIT_DATA_PATH;\nsecurity/selinux/hooks.c-1780-\t\tad.u.path = path;\n--\nsecurity/selinux/hooks.c-1786-\nsecurity/selinux/hooks.c:1787:\t\tad.type = LSM_AUDIT_DATA_FILE;\nsecurity/selinux/hooks.c-1788-\t\tad.u.file = file;\n--\nsecurity/selinux/hooks.c=1854=static int may_create(struct inode dir,\n--\nsecurity/selinux/hooks.c-1869-\nsecurity/selinux/hooks.c:1870:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-1871-\tad.u.dentry = dentry;\n--\nsecurity/selinux/hooks.c=1898=static int may_link(struct inode dir,\n--\nsecurity/selinux/hooks.c-1911-\nsecurity/selinux/hooks.c:1912:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-1913-\tad.u.dentry = dentry;\n--\nsecurity/selinux/hooks.c=1941=static inline int may_rename(struct inode old_dir,\n--\nsecurity/selinux/hooks.c-1957-\nsecurity/selinux/hooks.c:1958:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-1959-\n--\nsecurity/selinux/hooks.c=2111=static int selinux_binder_transfer_file(const struct cred from,\n--\nsecurity/selinux/hooks.c-2121-\nsecurity/selinux/hooks.c:2122:\tad.type = LSM_AUDIT_DATA_PATH;\nsecurity/selinux/hooks.c-2123-\tad.u.path = file-\u003ef_path;\n--\nsecurity/selinux/hooks.c=2344=static int selinux_bprm_creds_for_exec(struct linux_binprm bprm)\n--\nsecurity/selinux/hooks.c-2411-\nsecurity/selinux/hooks.c:2412:\tad.type = LSM_AUDIT_DATA_FILE;\nsecurity/selinux/hooks.c-2413-\tad.u.file = bprm-\u003efile;\n--\nsecurity/selinux/hooks.c=2793=static int selinux_sb_kern_mount(const struct super_block sb)\n--\nsecurity/selinux/hooks.c-2797-\nsecurity/selinux/hooks.c:2798:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-2799-\tad.u.dentry = sb-\u003es_root;\n--\nsecurity/selinux/hooks.c=2803=static int selinux_sb_statfs(struct dentry dentry)\n--\nsecurity/selinux/hooks.c-2807-\nsecurity/selinux/hooks.c:2808:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-2809-\tad.u.dentry = dentry-\u003ed_sb-\u003es_root;\n--\nsecurity/selinux/hooks.c=3017=static int selinux_inode_init_security_anon(struct inode inode,\n--\nsecurity/selinux/hooks.c-3072-\nsecurity/selinux/hooks.c:3073:\tad.type = LSM_AUDIT_DATA_ANONINODE;\nsecurity/selinux/hooks.c-3074-\tad.u.anonclass = name ? (const char )name-\u003ename : \"?\";\n--\nsecurity/selinux/hooks.c=3131=static int selinux_inode_follow_link(struct dentry dentry, struct inode inode,\n--\nsecurity/selinux/hooks.c-3137-\nsecurity/selinux/hooks.c:3138:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-3139-\tad.u.dentry = dentry;\n--\nsecurity/selinux/hooks.c=3147=static noinline int audit_inode_permission(struct inode inode,\n--\nsecurity/selinux/hooks.c-3153-\nsecurity/selinux/hooks.c:3154:\tad.type = LSM_AUDIT_DATA_INODE;\nsecurity/selinux/hooks.c-3155-\tad.u.inode = inode;\n--\nsecurity/selinux/hooks.c=3376=static int selinux_inode_setxattr(struct mnt_idmap idmap,\n--\nsecurity/selinux/hooks.c-3400-\nsecurity/selinux/hooks.c:3401:\tad.type = LSM_AUDIT_DATA_DENTRY;\nsecurity/selinux/hooks.c-3402-\tad.u.dentry = dentry;\n--\nsecurity/selinux/hooks.c=3562=static int selinux_path_notify(const struct path path, u64 mask,\n--\nsecurity/selinux/hooks.c-3569-\nsecurity/selinux/hooks.c:3570:\tad.type = LSM_AUDIT_DATA_PATH;\nsecurity/selinux/hooks.c-3571-\tad.u.path = path;\n--\nsecurity/selinux/hooks.c=3924=static int ioctl_has_perm(const struct cred cred, struct file file,\n--\nsecurity/selinux/hooks.c-3936-\nsecurity/selinux/hooks.c:3937:\tad.type = LSM_AUDIT_DATA_IOCTL_OP;\nsecurity/selinux/hooks.c-3938-\tad.u.op = \u0026ioctl;\n--\nsecurity/selinux/hooks.c=4049=static int backing_mounters_has_perm(const struct file file, u32 av)\n--\nsecurity/selinux/hooks.c-4065-\nsecurity/selinux/hooks.c:4066:\t\tad.type = LSM_AUDIT_DATA_PATH;\nsecurity/selinux/hooks.c-4067-\t\tad.u.path = layer-\u003epath;\n--\nsecurity/selinux/hooks.c=4146=static int selinux_mmap_file_common(struct file file, unsigned long prot,\n--\nsecurity/selinux/hooks.c-4154-\nsecurity/selinux/hooks.c:4155:\t\tad.type = LSM_AUDIT_DATA_FILE;\nsecurity/selinux/hooks.c-4156-\t\tad.u.file = file;\n--\nsecurity/selinux/hooks.c=4489=static int selinux_kernel_module_request(char kmod_name)\n--\nsecurity/selinux/hooks.c-4492-\nsecurity/selinux/hooks.c:4493:\tad.type = LSM_AUDIT_DATA_KMOD;\nsecurity/selinux/hooks.c-4494-\tad.u.kmod_name = kmod_name;\n--\nsecurity/selinux/hooks.c=4500=static int selinux_kernel_load_from_file(struct file file, u32 requested)\n--\nsecurity/selinux/hooks.c-4510-\nsecurity/selinux/hooks.c:4511:\tad.type = LSM_AUDIT_DATA_FILE;\nsecurity/selinux/hooks.c-4512-\tad.u.file = file;\n--\nsecurity/selinux/hooks.c=5120=static int __selinux_socket_bind(struct sock sk, struct sockaddr address, int addrlen)\n--\nsecurity/selinux/hooks.c-5185-\nsecurity/selinux/hooks.c:5186:\t\tad.type = LSM_AUDIT_DATA_NET;\nsecurity/selinux/hooks.c-5187-\t\tad.u.net = \u0026net;\n--\nsecurity/selinux/hooks.c=5259=static int selinux_socket_connect_helper(struct sock sk,\n--\nsecurity/selinux/hooks.c-5330-\nsecurity/selinux/hooks.c:5331:\t\tad.type = LSM_AUDIT_DATA_NET;\nsecurity/selinux/hooks.c-5332-\t\tad.u.net = \u0026net;\n--\nsecurity/selinux/hooks.c=6361=static int nlmsg_sock_has_extended_perms(struct sock sk, u32 perms, u16 nlmsg_type)\n--\nsecurity/selinux/hooks.c-6370-\nsecurity/selinux/hooks.c:6371:\tad.type = LSM_AUDIT_DATA_NLMSGTYPE;\nsecurity/selinux/hooks.c-6372-\tad.u.nlmsg_type = nlmsg_type;\n--\nsecurity/selinux/hooks.c=6455=static int ipc_has_perm(struct kern_ipc_perm ipc_perms,\n--\nsecurity/selinux/hooks.c-6463-\nsecurity/selinux/hooks.c:6464:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6465-\tad.u.ipc_id = ipc_perms-\u003ekey;\n--\nsecurity/selinux/hooks.c=6481=static int selinux_msg_queue_alloc_security(struct kern_ipc_perm msq)\n--\nsecurity/selinux/hooks.c-6489-\nsecurity/selinux/hooks.c:6490:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6491-\tad.u.ipc_id = msq-\u003ekey;\n--\nsecurity/selinux/hooks.c=6497=static int selinux_msg_queue_associate(struct kern_ipc_perm msq, int msqflg)\n--\nsecurity/selinux/hooks.c-6504-\nsecurity/selinux/hooks.c:6505:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6506-\tad.u.ipc_id = msq-\u003ekey;\n--\nsecurity/selinux/hooks.c=6540=static int selinux_msg_queue_msgsnd(struct kern_ipc_perm msq, struct msg_msg msg, int msqflg)\n--\nsecurity/selinux/hooks.c-6564-\nsecurity/selinux/hooks.c:6565:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6566-\tad.u.ipc_id = msq-\u003ekey;\n--\nsecurity/selinux/hooks.c=6583=static int selinux_msg_queue_msgrcv(struct kern_ipc_perm msq, struct msg_msg msg,\n--\nsecurity/selinux/hooks.c-6595-\nsecurity/selinux/hooks.c:6596:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6597-\tad.u.ipc_id = msq-\u003ekey;\n--\nsecurity/selinux/hooks.c=6608=static int selinux_shm_alloc_security(struct kern_ipc_perm shp)\n--\nsecurity/selinux/hooks.c-6616-\nsecurity/selinux/hooks.c:6617:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6618-\tad.u.ipc_id = shp-\u003ekey;\n--\nsecurity/selinux/hooks.c=6624=static int selinux_shm_associate(struct kern_ipc_perm shp, int shmflg)\n--\nsecurity/selinux/hooks.c-6631-\nsecurity/selinux/hooks.c:6632:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6633-\tad.u.ipc_id = shp-\u003ekey;\n--\nsecurity/selinux/hooks.c=6686=static int selinux_sem_alloc_security(struct kern_ipc_perm sma)\n--\nsecurity/selinux/hooks.c-6694-\nsecurity/selinux/hooks.c:6695:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6696-\tad.u.ipc_id = sma-\u003ekey;\n--\nsecurity/selinux/hooks.c=6702=static int selinux_sem_associate(struct kern_ipc_perm sma, int semflg)\n--\nsecurity/selinux/hooks.c-6709-\nsecurity/selinux/hooks.c:6710:\tad.type = LSM_AUDIT_DATA_IPC;\nsecurity/selinux/hooks.c-6711-\tad.u.ipc_id = sma-\u003ekey;\n--\nsecurity/selinux/hooks.c=7240=static int selinux_ib_pkey_access(void ib_sec, u64 subnet_prefix, u16 pkey_val)\n--\nsecurity/selinux/hooks.c-7251-\nsecurity/selinux/hooks.c:7252:\tad.type = LSM_AUDIT_DATA_IBPKEY;\nsecurity/selinux/hooks.c-7253-\tibpkey.subnet_prefix = subnet_prefix;\n--\nsecurity/selinux/hooks.c=7261=static int selinux_ib_endport_manage_subnet(void ib_sec, const char dev_name,\n--\nsecurity/selinux/hooks.c-7275-\nsecurity/selinux/hooks.c:7276:\tad.type = LSM_AUDIT_DATA_IBENDPORT;\nsecurity/selinux/hooks.c-7277-\tibendport.dev_name = dev_name;\n--\nsecurity/selinux/hooks.c=7609=static int selinux_uring_cmd(struct io_uring_cmd ioucmd)\n--\nsecurity/selinux/hooks.c-7615-\nsecurity/selinux/hooks.c:7616:\tad.type = LSM_AUDIT_DATA_FILE;\nsecurity/selinux/hooks.c-7617-\tad.u.file = file;\n" }
31/3	2026/08/29 22:25	llm	kmsan-evaluator	0m Model: gemini-3.7-flash Args: null Results: null Tokens: input: 13626 output: 235 thoughts: 1240 Thoughts: KMSAN Assessment: No Need Here Okay, so I've been carefully reviewing this diff, focusing on potential KMSAN needs. The crucial pieces, `ad.type` and `ad.u.path`, are set consistently, matching all the other audit data usages throughout the relevant `security/selinux/hooks.c` file. That's a good starting point. Now, let's break down the functions involved and assess for uninitialized memory use or kernel-to-user space data leaks. `inode_sid_has_perm` looks clean; it takes the needed audit data but seems to just wrap a call to `avc_has_perm`, a refactor splitting `inode_has_perm`. No issues there. `selinux_file_user_sid` appears to handle file metadata correctly. The more complex area is around the backing file structures, especially `selinux_backing_file_alloc`, `selinux_backing_file_free`, and `selinux_file_mprotect`. After digging in, I'm confident that the critical data in `bfsec->layers` are fully initialized. `selinux_backing_file_alloc` allocates the layers, copies existing ones, and populates the data, including a refcount bump for paths, making sure nothing is left dangling. `selinux_backing_file_free` correctly frees and puts the path for each layer. The permission checks in `backing_mounters_has_perm` also look okay. And finally, `selinux_file_mprotect` simply adds a call to backing mounters. No obvious issues there. The helper function `file_map_prot_to_av` just maps protection bits. I've specifically looked for data copies to userspace – none. I've also checked carefully for uninitialized memory usage. All `bfsec->layers` entries are fully initialized, and `bfsec` itself is zeroed during allocation. The common audit data (`common_audit_data ad`) is also populated correctly, following the standard SELinux pattern. Critically, there are no kernel-to-user copies that I can see (`copy_to_user`, `put_user`, socket options, etc.). There's no branching that depends on uninitialized variables, and all structures are either zeroed or fully initialized before being read or copied. Frankly, I think any bugs here would manifest as memory corruption, use-after-free, or refcounting issues. Those are already well-covered by KASAN and standard kernel checks. Based on the criteria, this patch really boils down to the types of bugs that KASAN is built to find. So, let's go back over the criteria again. 1. Kernel structures sent to user space where fields or structure padding might not be fully initialized/zeroed. No. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. No. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. No (all are fully initialized). 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. No. This falls squarely under the "KASAN covers it" category. All stack/heap structures touched or introduced by the patch are fully zeroed or initialized. The patch does not introduce any risk of uninitialized memory usage or info-leaks. Therefore, KMSAN is not needed here. KASAN is sufficient. I'm ready to mark `NeedsKMSAN=false` and submit the final response.
32/3	2026/08/29 22:25	tool	set-results	0m Args: { "KMSANReasoning": "The patch extends SELinux backing file tracking to handle multiple layers in stacked filesystems (such as overlayfs and erofs) by introducing intermediate backing layer structures, recording paths and SIDs, and validating mounter permissions during file mmap/mprotect operations.\n\nAll newly allocated heap structures (`backing_file_security_layer` arrays) are explicitly and fully initialized upon allocation before use or copying. The containing `backing_file_security_struct` blob is allocated via `kmem_cache_zalloc`. The audit data stack structure `struct common_audit_data ad` is properly configured with `type = LSM_AUDIT_DATA_PATH` and the path union member assigned before passing to the audit/AVC subsystem. No data is exposed or copied to user space, and there is no branching on uninitialized memory. Potential risks in this patch (such as lifetime issues, refcounting, path management, or out-of-bounds indexing) fall within the scope of KASAN rather than KMSAN.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch extends SELinux backing file tracking to handle multiple layers in stacked filesystems (such as overlayfs and erofs) by introducing intermediate backing layer structures, recording paths and SIDs, and validating mounter permissions during file mmap/mprotect operations.\n\nAll newly allocated heap structures (`backing_file_security_layer` arrays) are explicitly and fully initialized upon allocation before use or copying. The containing `backing_file_security_struct` blob is allocated via `kmem_cache_zalloc`. The audit data stack structure `struct common_audit_data ad` is properly configured with `type = LSM_AUDIT_DATA_PATH` and the path union member assigned before passing to the audit/AVC subsystem. No data is exposed or copied to user space, and there is no branching on uninitialized memory. Potential risks in this patch (such as lifetime issues, refcounting, path management, or out-of-bounds indexing) fall within the scope of KASAN rather than KMSAN.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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