[S390] init task memory faults.

Lock for mmap_sem is missing on page fault retry for init task
when it fails due to out of memory.

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 44f0cda7e72e..a393c308bb29 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -355,6 +355,7 @@ out_of_memory:
         up_read(&mm->mmap_sem);
         if (tsk->pid == 1) {
                 yield();
+                down_read(&mm->mmap_sem);
                 goto survive;
         }
         printk("VM: killing process %s\n", tsk->comm);