[PATCH] s390: kernel stack corruption

When an asynchronous interruption occurs during the execution of the
'critical section' within the generic interruption handling code (entry.S),
a faulty check for a userspace PSW may result in a corrupted kernel stack
pointer which subsequently triggers a stack overflow check.

Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/s390/kernel/entry.S

@@ -108,7 +108,7 @@ STACK_SIZE  = 1 << STACK_SHIFT
 	bl	BASED(0f)
 	l	%r14,BASED(.Lcleanup_critical)
 	basr	%r14,%r14
-	tm	0(%r12),0x01		# retest problem state after cleanup
+	tm	1(%r12),0x01		# retest problem state after cleanup
 	bnz	BASED(1f)
 0:	l	%r14,__LC_ASYNC_STACK	# are we already on the async stack ?
 	slr	%r14,%r15

arch/s390/kernel/entry64.S

@@ -101,7 +101,7 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NEED_RESCHED | _TIF_MCCK_PENDING)
 	clc	\psworg+8(8),BASED(.Lcritical_start)
 	jl	0f
 	brasl	%r14,cleanup_critical
-	tm	0(%r12),0x01		# retest problem state after cleanup
+	tm	1(%r12),0x01		# retest problem state after cleanup
 	jnz	1f
 0:	lg	%r14,__LC_ASYNC_STACK	# are we already on the async. stack ?
 	slgr	%r14,%r15