tree 8d1788a6a1b88190379926ce726bc6867ad98dd2
parent 803c2d2f84da9dc2619449994af34d27148ab20d
author Michael Neuling <mikey@neuling.org> 1387167163 +1100
committer Benjamin Herrenschmidt <benh@kernel.crashing.org> 1388372548 +1100

powerpc: Fix bad stack check in exception entry

In EXCEPTION_PROLOG_COMMON() we check to see if the stack pointer (r1)
is valid when coming from the kernel.  If it's not valid, we die but
with a nice oops message.

Currently we allocate a stack frame (subtract INT_FRAME_SIZE) before we
check to see if the stack pointer is negative.  Unfortunately, this
won't detect a bad stack where r1 is less than INT_FRAME_SIZE.

This patch fixes the check to compare the modified r1 with
-INT_FRAME_SIZE.  With this, bad kernel stack pointers (including NULL
pointers) are correctly detected again.

Kudos to Paulus for finding this.

Signed-off-by: Michael Neuling <mikey@neuling.org>
cc: stable@vger.kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>