[PATCH] powerpc: Sanitize stack pointer in signal handling code

[Benjamin Herrenschmidt]

> >Signed-off-by: Josh Boyer <jwboyer at linux.vnet.ibm.com>
> 
> Ben, this should look familiar.  It's based on your current -next branch.
> 
> If you agree, I can send it to the -stable team for .27, .28 and .29.

Patch looks good. I'll review more closely tomorrow morning and put it
in my -next branch, which I'll then ask Linux to pull. At this point, we
can have it backported into stable.

Cheers,
Ben.