linux-ext4 - Re: [PATCH] ext4: fix i_data_sem unlock order in ext4_ind

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Date: Thu, 4 Apr 2024 12:00:43 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Mikhail Ukhin <mish.uxin2012@...dex.ru>
Cc: Theodore Ts'o <tytso@....edu>, stable@...r.kernel.org,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	Michail Ivanov <iwanov-23@...ru>,
	Pavel Koshutin <koshutin.pavel@...dex.ru>,
	Artem Sadovnikov <ancowi69@...il.com>
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 <ancowi69@...il.com>

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>