[patch] s390: kernel stack corruption.

[Martin Schwidefsky]

Hi Andrew,
Peter discoverd another rather critical bug in entry.S.
This should go into 2.6.14 if possible.

blue skies,
  Martin.

---

[patch] s390: kernel stack corruption.

From: Peter Oberparleiter <peter.oberparleiter@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

diffstat:
 arch/s390/kernel/entry.S   |    2 +-
 arch/s390/kernel/entry64.S |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff -urpN linux-2.6/arch/s390/kernel/entry64.S linux-2.6-patched/arch/s390/kernel/entry64.S
--- linux-2.6/arch/s390/kernel/entry64.S	2005-09-15 15:31:03.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/entry64.S	2005-09-15 15:31:26.000000000 +0200
@@ -101,7 +101,7 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_
 	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
diff -urpN linux-2.6/arch/s390/kernel/entry.S linux-2.6-patched/arch/s390/kernel/entry.S
--- linux-2.6/arch/s390/kernel/entry.S	2005-09-15 15:31:03.000000000 +0200
+++ linux-2.6-patched/arch/s390/kernel/entry.S	2005-09-15 15:31:26.000000000 +0200
@@ -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
-
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