netdev - Re: [PATCH v2] [net] af_unix: return data from multiple SKBs on recv() with MSG

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Message-ID: <87d1xc7uf5.fsf@bytheb.org>
Date:	Sun, 20 Sep 2015 15:38:38 -0400
From:	Aaron Conole <aconole@...heb.org>
To:	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v2] [net] af_unix: return data from multiple SKBs on recv() with MSG_PEEK flag


Resending, I accidentally dropped the list.

> Eric Dumazet <eric.dumazet@...il.com> writes:
>
>> On Sun, 2015-09-20 at 15:07 -0400, Aaron Conole wrote:
>>> Eric Dumazet <eric.dumazet@...il.com> writes:
>>> 
>>> > On Sun, 2015-09-20 at 05:18 -0400, Aaron Conole wrote:
>>> >> From: Aaron Conole <aaron@...heb.org>
>>> >> 
>>> >
>>> > I am wondering what this is expected to do, and how this code would
>>> > possibly not trigger a crash.
>>> Are you suspecting it should crash from a possible double-lock case?
>>> On line 2125, there is an unconditional unlock, which should be 
>>> guaranteeing that there is no longer a condition to 'double lock' the
>>> socket.
>>
>> Not at all.
>>
>> I am suggesting there is a big difference between
>>
>> unix_state_lock(&sk);
>>
>> and
>>
>> unix_state_lock(sk);
>>
>> Can you see it ?

Wow!

That's an excellent catch, thank you! I did test the originally
submitted patch, and got no oops, bug, panic, etc (I usually have
panic_on_oops set to 1 when first testing new code).

I guess I got very lucky, somehow. I'll change this, and make sure
to retest.

I will also try to enhance the python case attached to the bug to
include a filepointer as well, and will repost a v3 when I have done
this.

Thanks,
-Aaron

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