From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754525AbYGRHEH (ORCPT ); Fri, 18 Jul 2008 03:04:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752912AbYGRHDz (ORCPT ); Fri, 18 Jul 2008 03:03:55 -0400 Received: from wf-out-1314.google.com ([209.85.200.171]:2851 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752794AbYGRHDx (ORCPT ); Fri, 18 Jul 2008 03:03:53 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=cY5dtcFQ3vB/7kEy4ZmM9SCith+JXXpq/3WFj2iYJP1IB/XrJjZo7S8Kyp2dvwqKl4 Qts9+ltszRm5qcctnZm2hJNA9ZHq6C0wW6t+/eHq6GqecgIhImzw2iTdhtUpq33/tVEY NoeB6PQmjGQrGL8j0nGqk6MBzN/ckq5umY7ME= Message-ID: <19f34abd0807180003m7bdf832g141777751d7ea563@mail.gmail.com> Date: Fri, 18 Jul 2008 09:03:50 +0200 From: "Vegard Nossum" To: "David Miller" Subject: Re: [bug, netconsole, SLUB] BUG skbuff_head_cache: Poison overwritten Cc: mingo@elte.hu, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, penberg@cs.helsinki.fi, rjw@sisk.pl In-Reply-To: <20080717.190315.186892939.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080717214222.GA29449@elte.hu> <19f34abd0807171615s5b477d4cr22d3e9444bcf65df@mail.gmail.com> <20080717.190315.186892939.davem@davemloft.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 18, 2008 at 4:03 AM, David Miller wrote: >> On Thu, Jul 17, 2008 at 11:42 PM, Ingo Molnar wrote: >> > >> > A regression to v2.6.26: >> > >> > I started getting this skb-head corruption message today, on a T60 >> > laptop with e1000: >> > >> > PM: Removing info for No Bus:vcs11 >> > device: 'vcs11': device_create_release >> > ============================================================================= >> > BUG skbuff_head_cache: Poison overwritten >> > ----------------------------------------------------------------------------- >> > >> > INFO: 0xf658ae9c-0xf658ae9c. First byte 0x6a instead of 0x6b >> >> 1. Notice the range. It's just a single byte. >> 2. Notice the value. It's just a ++. > > It's supposed to be 0x6b, this would be a "--" You're right! Oops. In my defence, I wrote that at 2 AM last night ;-) > Also it (more likely IMHO) could be clearing a flag with the value 0x01. It could be. But like I said in a later e-mail, the thing is likely sk_buff->truesize. Which is not a flags variable. It _is_ however, a counter, which is frequently -= and atomic_sub()ed. That field is also an int, not a byte like I suggested above. This is fine, though. "--" on an int can of course legitimately update/change just the lower byte of an int. But.. it could also be some random corruption coming from elsewhere. Maybe even bad RAM (it's just a single bit anyway). But that's less likely. Vegard -- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036