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Subject: Re: [held lock freed] Re: [GIT] Networking
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Ingo Molnar <mingo@elte.hu>, David Miller <davem@davemloft.net>,
        torvalds@linux-foundation.org, akpm@linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Thomas Gleixner <tglx@linutronix.de>
In-Reply-To: <201103211550.10694.arnd@arndb.de>
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	 <201103211550.10694.arnd@arndb.de>
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Date: Mon, 21 Mar 2011 15:55:32 +0100
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Le lundi 21 mars 2011 à 15:50 +0100, Arnd Bergmann a écrit :
> On Monday 21 March 2011, Eric Dumazet wrote:
> > [PATCH] ipx: fix ipx_release()
> > 
> > Commit b0d0d915d1d1a0 (remove the BKL) added a regression, because
> > sock_put() can free memory while we are going to use it later.
> > 
> > Fix is to delay sock_put() after release_sock().
> > 
> > Reported-by: Ingo Molnar <mingo@elte.hu>
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> 
> Your fix looks good, thanks Eric!
> 
> Acked-by: Arnd Bergmann <arnd@arndb.de>
> 
> I believe I made the same mistake in atalk_release and x25_release:
> 
> 8<------------
> net: fix atalk_release and x25_release
> 
> The recent BKL removal has introduced a use-after-free problem
> in multiple network protocols. This fixes the problem in appletalk
> and x25 by ensuring that we call the final sock_put() after
> releasing the socket lock.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


> diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
> index 4680b1e..b2cf1db 100644
> --- a/net/x25/af_x25.c
> +++ b/net/x25/af_x25.c
> @@ -669,8 +669,8 @@ static int x25_release(struct socket *sock)
>  
>  	sock_orphan(sk);
>  out:
> -	release_sock(sk);
>  	sock_put(sk);
> +	release_sock(sk);
>  	return 0;
>  }
>  

Hmm, x25_release() looks fine, I believe no fix is needed.