This is a note to let you know that I've just added the patch titled
powerpc: Fix bad stack check in exception entry
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-fix-bad-stack-check-in-exception-entry.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 90ff5d688e61f49f23545ffab6228bd7e87e6dc7 Mon Sep 17 00:00:00 2001
From: Michael Neuling <mikey@xxxxxxxxxxx>
Date: Mon, 16 Dec 2013 15:12:43 +1100
Subject: powerpc: Fix bad stack check in exception entry
From: Michael Neuling <mikey@xxxxxxxxxxx>
commit 90ff5d688e61f49f23545ffab6228bd7e87e6dc7 upstream.
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@xxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/exception-64s.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -265,7 +265,7 @@ do_kvm_##n: \
subi r1,r1,INT_FRAME_SIZE; /* alloc frame on kernel stack */ \
beq- 1f; \
ld r1,PACAKSAVE(r13); /* kernel stack to use */ \
-1: cmpdi cr1,r1,0; /* check if r1 is in userspace */ \
+1: cmpdi cr1,r1,-INT_FRAME_SIZE; /* check if r1 is in userspace */ \
blt+ cr1,3f; /* abort if it is */ \
li r1,(n); /* will be reloaded later */ \
sth r1,PACA_TRAP_SAVE(r13); \
Patches currently in stable-queue which might be from mikey@xxxxxxxxxxx are
queue-3.12/powerpc-fix-bad-stack-check-in-exception-entry.patch
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