linux-kernel - Re: [PATCH] tproxy: nf_tproxy_assign

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Message-ID: <1278835332.2538.51.camel@edumazet-laptop>
Date:	Sun, 11 Jul 2010 10:02:12 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Felipe W Damasio <felipewd@...il.com>,
	David Miller <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>,
	linux-kernel@...r.kernel.org, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tproxy: nf_tproxy_assign_sock() can handle tw sockets

Le dimanche 11 juillet 2010 à 08:19 +0300, Avi Kivity a écrit :
> On 07/10/2010 09:17 AM, Eric Dumazet wrote:
> >
> > Strange thing with your crash report is CR2 value, with unexpected value
> > of 000000000b388000 while RAX value is dce8dce85d415d41
> >
> > Faulting instruction is :
> >
> > 48 83 b8 b0 00 00 00 00   cmpq   $0x0,0xb0(%rax)
> >
> > So I would have expected CR2 being RAX+0xb0, but its not.
> >    
> 
> Nothing strange about it.  You only get page faults and valid cr2 for 
> canonical addresses (17 high order bits all equal).  In this case 
> rax+0xb0 is not a canonical address, so you got a general protection 
> fault instead, with cr2 unchanged.
> 

OK, thanks Avi for this information, as I was not aware of this.

So something overwrote sk->sk_prot pointer (or skb->sk pointer) with
some data.

tcp sockets are allocated from a dedicated kmem_cache (because of
SLAB_DESTROY_RCU attribute). Their sk->sk_prot should never change in
normal operation, since underlying memory cannot be reused by another
object type in kernel. It should be NULL or &tcp_prot

Felipe, please describe your configuration as much as possible.
It might be a driver bug with with special kind of network frames.

lsmod
lspci -v
ethtool -k eth0
ethtool -k eth1 (if applicable)



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