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Subject: Re: a problem tcp_v4_err()
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Patrick McHardy <kaber@trash.net>, David Lamparter <equinox@diac24.net>,
        Eric Paris <eparis@redhat.com>, Hua Zhong <hzhong@gmail.com>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        davem@davemloft.net, pekkas@netcore.fi, jmorris@namei.org,
        yoshfuji@linux-ipv6.org, paul.moore@hp.com
In-Reply-To: <20101112175715.GB16544@ms2.inr.ac.ru>
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	 <4CDD7145.8070606@trash.net>  <20101112175715.GB16544@ms2.inr.ac.ru>
Content-Type: text/plain; charset="UTF-8"
Date: Fri, 12 Nov 2010 19:12:58 +0100
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Le vendredi 12 novembre 2010 à 20:57 +0300, Alexey Kuznetsov a écrit :
> Hello!
> 
> I looked at tcp_v4_err() and found something strange. Quite non-trivial operations
> are performed on unlocked sockets. It looks like at least this BUG_ON():
> 
>                 skb = tcp_write_queue_head(sk);
>                 BUG_ON(!skb);
> 
> can be easily triggered.
> 
> Do I miss something?
> 

Hi Alexey !

I see socket is locked around line 368,

        bh_lock_sock(sk);
        /* If too many ICMPs get dropped on busy
         * servers this needs to be solved differently.
         */
        if (sock_owned_by_user(sk))
                NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);


Hmm, maybe some goto is missing ;)


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