s390/chsc: Add exception handler for CHSC instruction

commit 77759137248f34864a8f7a58bbcebfcf1047504a upstream.

Prevent kernel crashes due to unhandled exceptions raised by the CHSC
instruction which may for example be triggered by invalid ioctl data.

Fixes: 64150adf89df ("s390/cio: Introduce generic synchronous CHSC IOCTL")
Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/s390/cio/ioasm.c b/drivers/s390/cio/ioasm.c
index 8225da619014..4182f60124da 100644
--- a/drivers/s390/cio/ioasm.c
+++ b/drivers/s390/cio/ioasm.c
@@ -165,13 +165,15 @@ int tpi(struct tpi_info *addr)
 int chsc(void *chsc_area)
 {
         typedef struct { char _[4096]; } addr_type;
-        int cc;
+        int cc = -EIO;
 
         asm volatile(
                 "       .insn   rre,0xb25f0000,%2,0\n"
-                "       ipm     %0\n"
+                "0:     ipm     %0\n"
                 "       srl     %0,28\n"
-                : "=d" (cc), "=m" (*(addr_type *) chsc_area)
+                "1:\n"
+                EX_TABLE(0b, 1b)
+                : "+d" (cc), "=m" (*(addr_type *) chsc_area)
                 : "d" (chsc_area), "m" (*(addr_type *) chsc_area)
                 : "cc");
         trace_s390_cio_chsc(chsc_area, cc);