[S390] mm: handle kernel caused page fault oom situations

If e.g. copy_from_user() generates a page fault and the kernel runs
into an OOM situation the system might lock up.
If the OOM killer sends a SIG_KILL to the current process it can't
handle it since it is stuck in a copy_from_user() - page fault loop.

Fix this by adding the same fix as other architectures have.

E.g. the x86 variant f86268 "x86/mm: Handle mm_fault_error() in kernel
space"

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

1 files changed, 9 insertions, 7 deletions

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 105fa1071435..b57723aee848 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -245,9 +245,12 @@ static noinline void do_fault_error(struct pt_regs *regs, long int_code,
                 do_no_context(regs, int_code, trans_exc_code);
                 break;
         default: /* fault & VM_FAULT_ERROR */
-                if (fault & VM_FAULT_OOM)
-                        pagefault_out_of_memory();
-                else if (fault & VM_FAULT_SIGBUS) {
+                if (fault & VM_FAULT_OOM) {
+                        if (!(regs->psw.mask & PSW_MASK_PSTATE))
+                                do_no_context(regs, int_code, trans_exc_code);
+                        else
+                                pagefault_out_of_memory();
+                } else if (fault & VM_FAULT_SIGBUS) {
                         /* Kernel mode? Handle exceptions or die */
                         if (!(regs->psw.mask & PSW_MASK_PSTATE))
                                 do_no_context(regs, int_code, trans_exc_code);
@@ -429,10 +432,9 @@ int __handle_fault(unsigned long uaddr, unsigned long pgm_int_code, int write)
         access = write ? VM_WRITE : VM_READ;
         fault = do_exception(&regs, access, uaddr | 2);
         if (unlikely(fault)) {
-                if (fault & VM_FAULT_OOM) {
-                        pagefault_out_of_memory();
-                        fault = 0;
-                } else if (fault & VM_FAULT_SIGBUS)
+                if (fault & VM_FAULT_OOM)
+                        return -EFAULT;
+                else if (fault & VM_FAULT_SIGBUS)
                         do_sigbus(&regs, pgm_int_code, uaddr);
         }
         return fault ? -EFAULT : 0;