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

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Message-ID: <12c41697-e9ea-3326-b906-bf15a0a4dece@gmail.com>
Date:   Thu, 8 Jul 2021 09:52:19 +0800
From:   Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
To:     Jeff Layton <jlayton@...nel.org>, 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 8/7/21 1:06 am, Jeff Layton wrote:
> 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!
> 

Yep, there's no change outside of the commit message. But I think after 
the discussion and with config DEBUG_IRQFLAGS, that is fine.

Thanks again, Jeff!