ARM: 7913/1: fix framepointer check in unwind_frame

This patch fixes corner case when (fp + 4) overflows unsigned long,
for example: fp = 0xFFFFFFFF -> fp + 4 == 3.

Cc: <stable@vger.kernel.org>
Signed-off-by: NKonstantin Khlebnikov <k.khlebnikov@samsung.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/stacktrace.c

@@ -31,7 +31,7 @@ int notrace unwind_frame(struct stackframe *frame)
 	high = ALIGN(low, THREAD_SIZE);
 
 	/* check current frame pointer is within bounds */
-	if (fp < (low + 12) || fp + 4 >= high)
+	if (fp < low + 12 || fp > high - 4)
 		return -EINVAL;
 
 	/* restore the registers from the stack frame */