netdev - Re: __pskb_pull_tail oops from 2.6.35

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Date:	Tue, 27 Sep 2011 22:37:19 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Dave Jones <davej@...hat.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: __pskb_pull_tail oops from 2.6.35

Le mardi 27 septembre 2011 à 16:24 -0400, Dave Jones a écrit :
> On Tue, Sep 27, 2011 at 04:18:48PM -0400, David Miller wrote:
>  > From: Dave Jones <davej@...hat.com>
>  > Date: Tue, 27 Sep 2011 16:15:00 -0400
>  > 
>  > > It looks like it died in put_page..
>  > > 
>  > > <1>[  262.574991] IP: [<ffffffff810dca57>] put_page+0x10/0x7c
>  > > 
>  > > which is only called in one place..
>  > > 
>  > > 1267         for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
>  > > 1268                 if (skb_shinfo(skb)->frags[i].size <= eat) {
>  > > 1269                         put_page(skb_shinfo(skb)->frags[i].page);
>  > > 1270                         eat -= skb_shinfo(skb)->frags[i].size;
>  > > 1271                 } else {
>  > 
>  > That's a pretty serious corruption, all frag array entries from 0 to
>  > nr_frags should have valid, non-NULL page pointers.
>  > 
>  > Maybe a LRO/GRO bug?  There were a couple of those.
> 
> I'll see if I can talk him into trying a self-built kernel, as we're not
> rebasing f14 at this point in its life-cycle. If it turns out to still affect
> 3.x, I'll bring it up again.
> 

This could be a struct skb_shared_info -> nr_frags corruption

(Something was overflowing skb head and overflowing very beginning of
skb_shared_info in rare circumstances)

We had such bug in the past, I cant remember details right now.



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