Syzbot report following KERNEL BUG:
kernel BUG at fs/ext4/extents_status.c:899!
....
Call Trace:
<TASK>
ext4_cache_extents+0x13e/0x2d0 fs/ext4/extents.c:518
ext4_find_extent+0x8f6/0xd10 fs/ext4/extents.c:916
ext4_ext_map_blocks+0x1e2/0x5f30 fs/ext4/extents.c:4098
ext4_map_blocks+0x9ca/0x18a0 fs/ext4/inode.c:563
ext4_getblk+0x553/0x6b0 fs/ext4/inode.c:849
ext4_bread_batch+0x7c/0x550 fs/ext4/inode.c:923
__ext4_find_entry+0x482/0x1050 fs/ext4/namei.c:1600
ext4_lookup_entry fs/ext4/namei.c:1701 [inline]
ext4_lookup fs/ext4/namei.c:1769 [inline]
ext4_lookup+0x4fc/0x730 fs/ext4/namei.c:1760
__lookup_slow+0x24c/0x480 fs/namei.c:1707
lookup_slow fs/namei.c:1724 [inline]
walk_component+0x40f/0x6a0 fs/namei.c:2020
link_path_walk.part.0+0x7ef/0xf70 fs/namei.c:2347
link_path_walk fs/namei.c:2272 [inline]
path_openat+0x266/0x2940 fs/namei.c:3605
do_filp_open+0x1aa/0x400 fs/namei.c:3636
do_sys_openat2+0x16d/0x4d0 fs/open.c:1214
do_sys_open fs/open.c:1230 [inline]
__do_sys_openat fs/open.c:1246 [inline]
__se_sys_openat fs/open.c:1241 [inline]
__x64_sys_openat+0x13f/0x1f0 fs/open.c:1241
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
</TASK>
The reason is fast commit recovery path will skip block validation in
__ext4_iget(), it allows syzbot be able to mount a corrupted non-journal
filesystem and cause kernel BUG when accessing it.
Fix it by adding a condition checking.
Signed-off-by: Nguyen Dinh Phi <phind.uet@xxxxxxxxx>
Reported-by: syzbot+c7358a3cd05ee786eb31@xxxxxxxxxxxxxxxxxxxxxxxxx
---
fs/ext4/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 560e56b42829..66c86d85081e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4951,7 +4951,7 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
goto bad_inode;
} else if (!ext4_has_inline_data(inode)) {
/* validate the block references in the inode */
- if (!(EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY) &&
+ if (!(journal && EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY) &&
(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
(S_ISLNK(inode->i_mode) &&
!ext4_inode_is_fast_symlink(inode)))) {
--
2.25.1
