path: root/arch/powerpc/include/asm/exception-64s.h
diff options
authorMichael Neuling <mikey@neuling.org>2013-12-16 15:12:43 +1100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-09 12:24:22 -0800
commit4e639053aacb787a762e3dea49f4d3a6c13a52e7 (patch)
treeda3fcafdef54b150b414883d55a5a318c385bab6 /arch/powerpc/include/asm/exception-64s.h
parent9e23c5bb1507d413f86652feea3fb1c41cb6f99b (diff)
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@neuling.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/powerpc/include/asm/exception-64s.h')
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 07ca627e52c..e17d94d429a 100644
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -264,7 +264,7 @@ 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); \