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

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Message-ID: <20100814214618.GA8505@suse.de>
Date:	Sat, 14 Aug 2010 14:46:18 -0700
From:	Greg KH <gregkh@...e.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Grant Coady <gcoady.lk@...il.com>, linux-kernel@...r.kernel.org,
	stable@...nel.org, stable-review@...nel.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk
Subject: Re: [0/3] 2.6.27.52 stable review

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.

It's booting here, but I'm out of time and have to go on vacation until
Monday night and I'll pick this up on Tuesday again when I get back.

thanks,

greg k-h
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