From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932534Ab0HNDEV (ORCPT ); Fri, 13 Aug 2010 23:04:21 -0400 Received: from cantor2.suse.de ([195.135.220.15]:48827 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932475Ab0HNDEU (ORCPT ); Fri, 13 Aug 2010 23:04:20 -0400 Date: Fri, 13 Aug 2010 19:53:23 -0700 From: Greg KH To: Linus Torvalds Cc: Grant Coady , linux-kernel@vger.kernel.org, stable@kernel.org, stable-review@kernel.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk Subject: Re: [0/3] 2.6.27.52 stable review Message-ID: <20100814025323.GA4779@suse.de> References: <20100813214704.GA18960@kroah.com> <20100813230712.GA1703@suse.de> <20100814001158.GA2849@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 13, 2010 at 05:51:56PM -0700, Linus Torvalds wrote: > On Fri, Aug 13, 2010 at 5:11 PM, Greg KH wrote: > > > > That's a warning that current->mm is null.  I don't know enough about > > the mm subsystem to say if this is normal or not, and I don't at first > > glance, see how this patch could have caused this to happen. > > We call that whole "expand_stack()" through handle_mm_fault(), and > that's _not_ called just for the process itself. So "current->mm" is > sometimes simply the wrong thing to use - like when you access the VM > of another process (during fork for the argument setup of the new VM, > or during ptrace etc). > > Which is why I think commit 05fa199d45c should fix it. It makes the > stack expansion thing use the right mm. Which it just _happened_ to do > before, because it was always called just from the faulting code where > current->mm happened to be the right mm. > > But I really don't know if there might be other issues lurking too. Ok, I'll go add that commit, and I unpacked my older machine that runs the .27 kernel and will beat on it with that box tomorrow to see if anything else pops up. thanks, greg k-h