[S390] smp: fix sigp sense handling

sigp sense only returns the status of a cpu if it is non zero. If the
status of the sensed cpu is all zeros condition code 0 (accpeted) is
set and no status bits are returned.
The current code however assumes that a status was returned and tests
bits in it. This means uninitalized data is accessed with random
results.
Worst case is that the code that checks if cpu is offline on cpu
hotplug assumes that the target cpu is offline while it is still
running. This leads potentially to memory corruption since resources
that are still needed by the target cpu will be freed and could be
resused while still in use.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/s390/kernel/swsusp_asm64.S b/arch/s390/kernel/swsusp_asm64.S
index 0f4ef3b856d9..0c26cc1898ec 100644
--- a/arch/s390/kernel/swsusp_asm64.S
+++ b/arch/s390/kernel/swsusp_asm64.S
@@ -207,6 +207,7 @@ restart_suspend:
         llgh    %r2,0(%r1)
 7:
         sigp    %r9,%r2,__SIGP_SENSE    /* Wait for resume CPU */
+        brc     8,7b                    /* accepted, status 0, still running */
         brc     2,7b                    /* busy, try again */
         tmll    %r9,0x40                /* Test if resume CPU is stopped */
         jz      7b