From: Nico Boehr nrb@linux.ibm.com
commit c9bfb460c3e4da2462e16b0f0b200990b36b1dd2 upstream.
Since commit 1179f170b6f0 ("s390: fix fpu restore in entry.S"), the sie_block pointer is located at empty1[1], but in sie_block() it was taken from empty1[0].
This leads to a random pointer being dereferenced, possibly causing system crash.
This problem can be observed when running a simple guest with an endless loop and recording the cpu-clock event:
sudo perf kvm --guestvmlinux=<guestkernel> --guest top -e cpu-clock
With this fix, the correct guest address is shown.
Fixes: 1179f170b6f0 ("s390: fix fpu restore in entry.S") Cc: stable@vger.kernel.org Acked-by: Christian Borntraeger borntraeger@de.ibm.com Acked-by: Claudio Imbrenda imbrenda@linux.ibm.com Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Nico Boehr nrb@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/kernel/perf_event.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/s390/kernel/perf_event.c +++ b/arch/s390/kernel/perf_event.c @@ -51,7 +51,7 @@ static struct kvm_s390_sie_block *sie_bl if (!stack) return NULL;
- return (struct kvm_s390_sie_block *) stack->empty1[0]; + return (struct kvm_s390_sie_block *)stack->empty1[1]; }
static bool is_in_guest(struct pt_regs *regs)