s390/chsc: Add exception handler for CHSC instruction

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")
Cc: <stable@vger.kernel.org> # v3.11+
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>

diff --git a/drivers/s390/cio/ioasm.c b/drivers/s390/cio/ioasm.c
index 8225da6190148a44e5a729d9d56a186ca0da6dfe..4182f60124da1a9cf114313ee69cf52ce5ac6039 100644 (file)
--- 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);