Fuzzing reports a possible deadlock in jbd2_log_wait_commit.

The problem occurs in ext4_ind_migrate due to an incorrect order of
unlocking of the journal and write semaphores - the order of unlocking
must be the reverse of the order of locking.

Found by Linux Verification Center (linuxtesting.org) with syzkaller.

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Artem Sadovnikov <ancowi69@gmail.com>
Signed-off-by: Mikhail Ukhin <mish.uxin2012@yandex.ru>
---
 v2: New addresses have been added and Ritesh Harjani has been noted as a
 reviewer.
 fs/ext4/migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index b0ea646454ac..59290356aa5b 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -663,8 +663,8 @@ int ext4_ind_migrate(struct inode *inode)
 	if (unlikely(ret2 && !ret))
 		ret = ret2;
 errout:
-	ext4_journal_stop(handle);
 	up_write(&EXT4_I(inode)->i_data_sem);
+	ext4_journal_stop(handle);
 out_unlock:
 	percpu_up_write(&sbi->s_writepages_rwsem);
 	return ret;
-- 
2.25.1

On Sat, Apr 06, 2024 at 12:08:03AM +0300, Mikhail Ukhin wrote:
> Fuzzing reports a possible deadlock in jbd2_log_wait_commit.
> 
> The problem occurs in ext4_ind_migrate due to an incorrect order of
> unlocking of the journal and write semaphores - the order of unlocking
> must be the reverse of the order of locking.
> 
> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
> 
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> Signed-off-by: Artem Sadovnikov <ancowi69@gmail.com>
> Signed-off-by: Mikhail Ukhin <mish.uxin2012@yandex.ru>

Thanks.  This has been addressed by commit 00d873c17e29 ("ext4: avoid
deadlock in fs reclaim with page writeback"), with the same code
change.

						- Ted