linux-kernel - Re: [PATCH] sock: Fix sk_sleep return invalid pointer

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Message-ID: <f80fcd476a230c354bf9758762250c43a1f3d5cc.camel@redhat.com>
Date:   Tue, 22 Aug 2023 17:31:00 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     eadavis@...a.com,
        syzbot+666c97e4686410e79649@...kaller.appspotmail.com
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        linux-hams@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, ralf@...ux-mips.org,
        syzkaller-bugs@...glegroups.com, hdanton@...a.com
Subject: Re: [PATCH] sock: Fix sk_sleep return invalid pointer

On Tue, 2023-08-22 at 20:44 +0800, eadavis@...a.com wrote:
> From: Edward AD <eadavis@...a.com>
> 
> The parameter sk_sleep(sk) passed in when calling prepare_to_wait may 
> return an invalid pointer due to nr-release reclaiming the sock.
> Here, schedule_timeout_interruptible is used to replace the combination 
> of 'prepare_to_wait, schedule, finish_wait' to solve the problem.
> 
> Reported-and-tested-by: syzbot+666c97e4686410e79649@...kaller.appspotmail.com
> Signed-off-by: Edward AD <eadavis@...a.com>

This looks wrong. No syscall should race with sock_release(). It looks
like you are papering over the real issue.

As the reproducer shows a disconnect on an connected socket, I'm wild
guessing something alike 4faeee0cf8a5d88d63cdbc3bab124fb0e6aed08c
should be more appropriate.

Cheers,

Paolo