linux-kernel - Re: [stable] [Stable-review] [0/3] 2.6.27.52 stable review

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Date:	Sat, 14 Aug 2010 11:47:25 -0700
From:	Greg KH <greg@...ah.com>
To:	Willy Tarreau <w@....eu>
Cc:	Greg KH <gregkh@...e.de>, Grant Coady <gcoady.lk@...il.com>,
	linux-kernel@...r.kernel.org, stable@...nel.org,
	akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	stable-review@...nel.org, alan@...rguk.ukuu.org.uk
Subject: Re: [stable] [Stable-review] [0/3] 2.6.27.52 stable review

On Sat, Aug 14, 2010 at 07:43:35AM +0200, Willy Tarreau wrote:
> On Fri, Aug 13, 2010 at 07:53:23PM -0700, Greg KH wrote:
> > On Fri, Aug 13, 2010 at 05:51:56PM -0700, Linus Torvalds wrote:
> > > On Fri, Aug 13, 2010 at 5:11 PM, Greg KH <gregkh@...e.de> 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.
> 
> Greg, I confirm that 05fa199d45c fixes the warnings. I did not have them
> in .51, got them with .52-rc1 and got rid of it with the patch above.

Wonderful.  I've released a 2.6.27.52-rc2 with this fix in it.  I'm
building it and will test it on my box now.  The full patch is below if
anyone wants to try it out.

Odds are it will need whatever patch Linus is currently working on for
mainline, so I'll hold off on releasing a real release until that is all
worked out.

thanks,

greg k-h


View attachment "patch-2.6.27.52-rc2" of type "text/plain" (2891 bytes)