From: Tejas Bharambe <tejas.bharambe@outlook.com> stable inclusion from stable-v6.12.80 commit 407c944f217c17d4343148011acafebc604d55e1 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14192 CVE: CVE-2026-31449 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 2acb5c12ebd860f30e4faf67e6cc8c44ddfe5fe8 upstream. ext4_ext_correct_indexes() walks up the extent tree correcting index entries when the first extent in a leaf is modified. Before accessing path[k].p_idx->ei_block, there is no validation that p_idx falls within the valid range of index entries for that level. If the on-disk extent header contains a corrupted or crafted eh_entries value, p_idx can point past the end of the allocated buffer, causing a slab-out-of-bounds read. Fix this by validating path[k].p_idx against EXT_LAST_INDEX() at both access sites: before the while loop and inside it. Return -EFSCORRUPTED if the index pointer is out of range, consistent with how other bounds violations are handled in the ext4 extent tree code. Reported-by: syzbot+04c4e65cab786a2e5b7e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=04c4e65cab786a2e5b7e Signed-off-by: Tejas Bharambe <tejas.bharambe@outlook.com> Link: https://patch.msgid.link/JH0PR06MB66326016F9B6AD24097D232B897CA@JH0PR06MB663... Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Zizhi Wo <wozizhi@huawei.com> --- fs/ext4/extents.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index acbce47b203b..ee91ab4901f2 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1749,10 +1749,17 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode, k = depth - 1; border = path[depth].p_ext->ee_block; err = ext4_ext_get_access(handle, inode, path + k); if (err) return err; + if (unlikely(path[k].p_idx > EXT_LAST_INDEX(path[k].p_hdr))) { + EXT4_ERROR_INODE(inode, + "path[%d].p_idx %p > EXT_LAST_INDEX %p", + k, path[k].p_idx, + EXT_LAST_INDEX(path[k].p_hdr)); + return -EFSCORRUPTED; + } path[k].p_idx->ei_block = border; err = ext4_ext_dirty(handle, inode, path + k); if (err) return err; @@ -1761,10 +1768,18 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode, if (path[k+1].p_idx != EXT_FIRST_INDEX(path[k+1].p_hdr)) break; err = ext4_ext_get_access(handle, inode, path + k); if (err) goto clean; + if (unlikely(path[k].p_idx > EXT_LAST_INDEX(path[k].p_hdr))) { + EXT4_ERROR_INODE(inode, + "path[%d].p_idx %p > EXT_LAST_INDEX %p", + k, path[k].p_idx, + EXT_LAST_INDEX(path[k].p_hdr)); + err = -EFSCORRUPTED; + goto clean; + } path[k].p_idx->ei_block = border; err = ext4_ext_dirty(handle, inode, path + k); if (err) goto clean; } -- 2.52.0