linux-kernel - Re: [PATCH v3 0/2] fcntl: fix potential deadlocks

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Date:   Wed, 07 Jul 2021 13:06:07 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        bfields@...ldses.org, viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org, gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH v3 0/2] fcntl: fix potential deadlocks

On Wed, 2021-07-07 at 15:43 +0800, Desmond Cheong Zhi Xi wrote:
> Hi,
> 
> Sorry for the delay between v1 and v2, there was an unrelated issue with Syzbot testing.
> 
> Syzbot reports a possible irq lock inversion dependency:
> https://syzkaller.appspot.com/bug?id=923cfc6c6348963f99886a0176ef11dcc429547b
> 
> While investigating this error, I discovered that multiple similar lock inversion scenarios can occur. Hence, this series addresses potential deadlocks for two classes of locks, one in each patch:
> 
> 1. Fix potential deadlocks for &fown_struct.lock
> 
> 2. Fix potential deadlock for &fasync_struct.fa_lock
> 
> v2 -> v3:
> - Removed WARN_ON_ONCE, keeping elaboration for why read_lock_irq is safe to use in the commit message. As suggested by Greg KH.
> 
> v1 -> v2:
> - Added WARN_ON_ONCE(irqs_disabled()) before calls to read_lock_irq, and added elaboration in the commit message. As suggested by Jeff Layton.
> 
> Best wishes,
> Desmond
> 
> Desmond Cheong Zhi Xi (2):
>   fcntl: fix potential deadlocks for &fown_struct.lock
>   fcntl: fix potential deadlock for &fasync_struct.fa_lock
> 
>  fs/fcntl.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 

Looks like these patches are identical to the v1 set, so I'm just going
to leave those in place since linux-next already has them. Let me know
if I've missed something though.

Thanks!
-- 
Jeff Layton <jlayton@...nel.org>