[3.5.y.z extended stable] Patch "powerpc: Fix bad stack check in exception entry" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Wed Jan 8 14:21:04 UTC 2014
This is a note to let you know that I have just added a patch titled
powerpc: Fix bad stack check in exception entry
to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From 9bb299b2520886a3a1f4cbfe0d79ba97ebb75bf2 Mon Sep 17 00:00:00 2001
From: Michael Neuling <mikey at neuling.org>
Date: Mon, 16 Dec 2013 15:12:43 +1100
Subject: powerpc: Fix bad stack check in exception entry
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 at neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
arch/powerpc/include/asm/exception-64s.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 6afb13a..241d2f3 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -163,7 +163,7 @@ 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); \
--
1.8.3.2
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