* [PATCH] ext4: Fix timer use-after-free on failed mount
@ 2021-03-15 16:59 Jan Kara
2021-03-21 4:28 ` Theodore Ts'o
0 siblings, 1 reply; 2+ messages in thread
From: Jan Kara @ 2021-03-15 16:59 UTC (permalink / raw)
To: Ted Tso; +Cc: linux-ext4, Jan Kara, syzbot+628472a2aac693ab0fcd, stable
When filesystem mount fails because of corrupted filesystem we first
cancel the s_err_report timer reminding fs errors every day and only
then we flush s_error_work. However s_error_work may report another fs
error and re-arm timer thus resulting in timer use-after-free. Fix the
problem by first flushing the work and only after that canceling the
s_err_report timer.
Reported-by: syzbot+628472a2aac693ab0fcd@syzkaller.appspotmail.com
Fixes: 2d01ddc86606 ("ext4: save error info to sb through journal if available")
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/ext4/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ad34a37278cd..2e3d4c5c2eb4 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5149,8 +5149,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
failed_mount3a:
ext4_es_unregister_shrinker(sbi);
failed_mount3:
- del_timer_sync(&sbi->s_err_report);
flush_work(&sbi->s_error_work);
+ del_timer_sync(&sbi->s_err_report);
if (sbi->s_mmp_tsk)
kthread_stop(sbi->s_mmp_tsk);
failed_mount2:
--
2.26.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] ext4: Fix timer use-after-free on failed mount
2021-03-15 16:59 [PATCH] ext4: Fix timer use-after-free on failed mount Jan Kara
@ 2021-03-21 4:28 ` Theodore Ts'o
0 siblings, 0 replies; 2+ messages in thread
From: Theodore Ts'o @ 2021-03-21 4:28 UTC (permalink / raw)
To: Jan Kara; +Cc: linux-ext4, syzbot+628472a2aac693ab0fcd, stable
On Mon, Mar 15, 2021 at 05:59:06PM +0100, Jan Kara wrote:
> When filesystem mount fails because of corrupted filesystem we first
> cancel the s_err_report timer reminding fs errors every day and only
> then we flush s_error_work. However s_error_work may report another fs
> error and re-arm timer thus resulting in timer use-after-free. Fix the
> problem by first flushing the work and only after that canceling the
> s_err_report timer.
>
> Reported-by: syzbot+628472a2aac693ab0fcd@syzkaller.appspotmail.com
> Fixes: 2d01ddc86606 ("ext4: save error info to sb through journal if available")
> CC: stable@vger.kernel.org
> Signed-off-by: Jan Kara <jack@suse.cz>
Thanks, applied.
- Ted
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-03-15 16:59 [PATCH] ext4: Fix timer use-after-free on failed mount Jan Kara
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