In qnx6_iget(), raw_inode->di_filelevels is read from disk without upper bounds checking. If raw_inode->di_filelevels exceeds QNX6_PTR_MAX_LEVELS (defined as 5 in include/linux/qnx6_fs.h), qnx6_block_map() performs out-of-bounds reads past di_block_ptr when dereferencing indirect tree levels. Validate raw_inode->di_filelevels against QNX6_PTR_MAX_LEVELS in qnx6_iget() and return -EIO if it exceeds 5. Tested in QEMU against tip of mainline commit 62f4c998b297 ("Merge tag 'parisc-for-7.3-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux") using a loop-device reproducer mounting a crafted QNX6 image with di_filelevels = 20: on the unfixed kernel, mounting triggered a buffer_head refcount underflow warning ("VFS: brelse: Trying to free free buffer"); whereas with this fix applied, qnx6_iget() cleanly rejects the corrupted inode with -EIO and logs "qnx6: bad filelevels 20 (max 5) on dev loop0, inode 1". Fixes: 5d026c724220 ("fs: initial qnx6fs addition") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng --- Changes in v4: - Rebased cleanly onto upstream mainline commit 62f4c998b297. - Added QEMU test procedure and verification details in commit message body. - Updated commit description to state QNX6_PTR_MAX_LEVELS is 5 as noted by Matthias Goergens. fs/qnx6/inode.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/qnx6/inode.c b/fs/qnx6/inode.c index a15bb03f0ec3..e61c33f2e146 100644 --- a/fs/qnx6/inode.c +++ b/fs/qnx6/inode.c @@ -561,6 +561,14 @@ struct inode *qnx6_iget(struct super_block *sb, unsigned ino) sizeof(raw_inode->di_block_ptr)); ei->di_filelevels = raw_inode->di_filelevels; + if (ei->di_filelevels > QNX6_PTR_MAX_LEVELS) { + pr_err("bad filelevels %u (max %u) on dev %s, inode %u\n", + ei->di_filelevels, QNX6_PTR_MAX_LEVELS, sb->s_id, ino); + folio_release_kmap(folio, raw_inode); + iget_failed(inode); + return ERR_PTR(-EIO); + } + if (S_ISREG(inode->i_mode)) { inode->i_fop = &generic_ro_fops; inode->i_mapping->a_ops = &qnx6_aops; -- 2.55.0.1082.g2b9226bbc0-goog