[S390] check addressing mode in s390_enable_sie

The sie instruction requires address spaces to be switched
to run proper. This patch verifies that this is the case
in s390_enable_sie, otherwise the kernel would crash badly
as soon as the process runs into sie.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index 6b6ddc4ea02b..9bf86125f6f3 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -258,6 +258,10 @@ int s390_enable_sie(void)
         struct task_struct *tsk = current;
         struct mm_struct *mm, *old_mm;
 
+        /* Do we have switched amode? If no, we cannot do sie */
+        if (!switch_amode)
+                return -EINVAL;
+
         /* Do we have pgstes? if yes, we are done */
         if (tsk->mm->context.has_pgste)
                 return 0;