[S390] take mmap_sem when walking guest page table

gmap_fault needs to walk the guest page table. However, parts of
that may change if some other thread does munmap. In that case
gmap_unmap_notifier will also unmap the corresponding parts from
the guest page table. We need to take mmap_sem in order to serialize
these operations.
do_exception now calls __gmap_fault with mmap_sem held which does
not get exported to modules. The exported function, which is called
from KVM, now takes mmap_sem.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index de3af0c053c0..1766def5bc3f 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -307,7 +307,7 @@ static inline int do_exception(struct pt_regs *regs, int access,
 
 #ifdef CONFIG_PGSTE
         if (test_tsk_thread_flag(current, TIF_SIE) && S390_lowcore.gmap) {
-                address = gmap_fault(address,
+                address = __gmap_fault(address,
                                      (struct gmap *) S390_lowcore.gmap);
                 if (address == -EFAULT) {
                         fault = VM_FAULT_BADMAP;