hfs_cat_find_brec() first resolves a catalog thread record by CNID and then looks up the corresponding catalog record by parent/name. On a corrupted filesystem image, the second lookup may find a record whose CNID does not match the CNID that was requested. Validate the record found by the second lookup before returning it. Read the already-found record with hfs_bnode_read(), require the exact fixed size for file and directory records, reject other record types, and verify that the stored CNID matches the requested CNID. Also validate reserved CNIDs in hfs_read_inode() before populating the inode, propagate hfs_read_inode() failures from the resource-fork lookup path, and reject bad resource-fork and root inodes. Keep hfs_write_inode() unchanged, so corrupted catalog records are rejected before reaching its existing reserved-CNID BUG() path. Reported-by: syzbot+97e301b4b82ae803d21b@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=97e301b4b82ae803d21b Cc: George Anthony Vernon Cc: Tetsuo Handa Signed-off-by: David Maximiliano Hermitte --- Changes in v4: - Combine the catalog record length validation into one check. - Require exact sizes for file and directory catalog records. - Keep hfs_write_inode() unchanged following maintainer feedback. - Revalidate the exact final patch with the HFS build and QEMU repro. Changes in v3: - Drop the stray blank line in hfs_file_lookup(). Changes in v2: - Use size_t for the catalog record length. - Reject catalog records larger than hfs_cat_rec. - Treat non-file/non-directory records as invalid. - Propagate hfs_read_inode() failures from resource-fork lookup. - Reject bad resource-fork and root inodes. fs/hfs/catalog.c | 41 ++++++++++++++++++++++++++++++++++++++++- fs/hfs/hfs_fs.h | 19 +++++++++++++++++++ fs/hfs/inode.c | 12 +++++++++--- fs/hfs/super.c | 5 +++++ 4 files changed, 73 insertions(+), 4 deletions(-) diff --git a/fs/hfs/catalog.c b/fs/hfs/catalog.c index 1bfa36d71e24..e672a4ba6dc7 100644 --- a/fs/hfs/catalog.c +++ b/fs/hfs/catalog.c @@ -182,6 +182,40 @@ int hfs_cat_keycmp(const btree_key *key1, const btree_key *key2) key2->cat.CName.name, key2->cat.CName.len); } +static int hfs_cat_validate_found_cnid(struct hfs_find_data *fd, u32 cnid) +{ + hfs_cat_rec rec; + u32 found_cnid; + size_t rec_len; + + rec_len = fd->entrylength; + if (rec_len <= 0 || rec_len > sizeof(rec)) + return -EIO; + + memset(&rec, 0, sizeof(rec)); + hfs_bnode_read(fd->bnode, &rec, fd->entryoffset, rec_len); + + switch (rec.type) { + case HFS_CDR_FIL: + if (rec_len != sizeof(struct hfs_cat_file)) + return -EIO; + found_cnid = be32_to_cpu(rec.file.FlNum); + break; + case HFS_CDR_DIR: + if (rec_len != sizeof(struct hfs_cat_dir)) + return -EIO; + found_cnid = be32_to_cpu(rec.dir.DirID); + break; + default: + return -EIO; + } + + if (found_cnid != cnid) + return -EIO; + + return 0; +} + /* Try to get a catalog entry for given catalog id */ // move to read_super??? int hfs_cat_find_brec(struct super_block *sb, u32 cnid, @@ -208,7 +242,12 @@ int hfs_cat_find_brec(struct super_block *sb, u32 cnid, return -EIO; } memcpy(fd->search_key->cat.CName.name, rec.thread.CName.name, len); - return hfs_brec_find(fd); + + res = hfs_brec_find(fd); + if (res) + return res; + + return hfs_cat_validate_found_cnid(fd, cnid); } static inline diff --git a/fs/hfs/hfs_fs.h b/fs/hfs/hfs_fs.h index f3624514fcb0..670638f17438 100644 --- a/fs/hfs/hfs_fs.h +++ b/fs/hfs/hfs_fs.h @@ -155,6 +155,25 @@ extern int hfs_cat_move(u32 cnid, struct inode *src_dir, extern void hfs_cat_build_key(struct super_block *sb, btree_key *key, u32 parent, const struct qstr *name); +/* + * Validate the CNID of a catalog record. + */ +static inline bool hfs_is_valid_cnid(u32 cnid, u8 type) +{ + if (likely(cnid >= HFS_FIRSTUSER_CNID)) + return true; + + switch (cnid) { + case HFS_ROOT_CNID: + return type == HFS_CDR_DIR; + case HFS_EXT_CNID: + case HFS_CAT_CNID: + return type == HFS_CDR_FIL; + default: + return false; + } +} + /* dir.c */ extern const struct file_operations hfs_dir_operations; extern const struct inode_operations hfs_dir_inode_operations; diff --git a/fs/hfs/inode.c b/fs/hfs/inode.c index ac4a9055c5c0..ee10a9257a13 100644 --- a/fs/hfs/inode.c +++ b/fs/hfs/inode.c @@ -367,6 +367,9 @@ static int hfs_read_inode(struct inode *inode, void *data) rec = idata->rec; switch (rec->type) { case HFS_CDR_FIL: + if (!hfs_is_valid_cnid(be32_to_cpu(rec->file.FlNum), rec->type)) + return -EIO; + if (!HFS_IS_RSRC(inode)) { hfs_inode_read_fork(inode, rec->file.ExtRec, rec->file.LgLen, rec->file.PyLen, be16_to_cpu(rec->file.ClpSize)); @@ -390,6 +393,9 @@ static int hfs_read_inode(struct inode *inode, void *data) inode->i_mapping->a_ops = &hfs_aops; break; case HFS_CDR_DIR: + if (!hfs_is_valid_cnid(be32_to_cpu(rec->dir.DirID), rec->type)) + return -EIO; + inode->i_ino = be32_to_cpu(rec->dir.DirID); inode->i_size = be16_to_cpu(rec->dir.Val) + 2; HFS_I(inode)->fs_blocks = 0; @@ -571,12 +577,12 @@ static struct dentry *hfs_file_lookup(struct inode *dir, struct dentry *dentry, res = hfs_brec_read(&fd, &rec, sizeof(rec)); if (!res) { struct hfs_iget_data idata = { NULL, &rec }; - hfs_read_inode(inode, &idata); + res = hfs_read_inode(inode, &idata); } hfs_find_exit(&fd); - if (res) { + if (res || is_bad_inode(inode)) { iput(inode); - return ERR_PTR(res); + return ERR_PTR(-EIO); } HFS_I(inode)->rsrc_inode = dir; HFS_I(dir)->rsrc_inode = inode; diff --git a/fs/hfs/super.c b/fs/hfs/super.c index a466c401f6bb..98b80795bcde 100644 --- a/fs/hfs/super.c +++ b/fs/hfs/super.c @@ -372,6 +372,11 @@ static int hfs_fill_super(struct super_block *sb, struct fs_context *fc) if (!root_inode) goto bail_no_root; + if (is_bad_inode(root_inode)) { + iput(root_inode); + goto bail_no_root; + } + set_default_d_op(sb, &hfs_dentry_operations); res = -ENOMEM; sb->s_root = d_make_root(root_inode); -- 2.43.0