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authorMichael Neuling <mikey@neuling.org>2013-12-16 15:12:43 +1100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-08 09:42:11 -0800
commit4e6cc83041aacf32013022d922c34230ee6e6e90 (patch)
treeddccdec6b806662e471834a8b2c8f7e6835f4b7c /arch
parent7110adb76087508116e4ce1496b8ca7a57e2d85d (diff)
downloadlinux-linaro-stable-4e6cc83041aacf32013022d922c34230ee6e6e90.tar.gz
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')
-rw-r--r--arch/powerpc/include/asm/exception-64s.h2
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 6afb13ad1611..241d2f305307 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); \