Re: [0/3] 2.6.27.52 stable review

[Greg KH]

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@xxxxxxx> 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
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