2024-04-04 09:56:22

by Mikhail Ukhin

Subject: [PATCH] ext4: fix i_data_sem unlock order in ext4_ind_migrate()

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.

Signed-off-by: Artem Sadovnikov <[email protected]>
---
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 d98ac2af8199..a5e1492bbaaa 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:
ext4_writepages_up_write(inode->i_sb, alloc_ctx);
return ret;
--
2.25.1

2024-04-04 10:01:02

by Greg Kroah-Hartman

Subject: Re: [PATCH] ext4: fix i_data_sem unlock order in ext4_ind_migrate()

On Thu, Apr 04, 2024 at 12:50:00PM +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.
>
> Signed-off-by: Artem Sadovnikov <[email protected]>

Does not match your From: line :(

> ---
> 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 d98ac2af8199..a5e1492bbaaa 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:
> ext4_writepages_up_write(inode->i_sb, alloc_ctx);
> return ret;
> --
> 2.25.1
>
>

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>