Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 058/129] powerpc: Fix bad stack check in exception entry | Date | Mon, 6 Jan 2014 14:38:07 -0800 |
| |
3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Michael Neuling <mikey@neuling.org>
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>
--- 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 @@ -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); \
| |