[Qemu-devel] [PULL 05/22] s390x/virtio-hcall: Add range check for hypervisor call

[Christian Borntraeger <borntraeger@de.ibm.com>]

From: Thomas Huth <thuth@linux.vnet.ibm.com>

The handler for diag 500 did not check whether the requested function
was in the supported range, so illegal values could crash QEMU in the
worst case.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
CC: qemu-stable@nongnu.org
---
 hw/s390x/s390-virtio-hcall.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/hw/s390x/s390-virtio-hcall.c b/hw/s390x/s390-virtio-hcall.c
index ee62649..0e328d8 100644
--- a/hw/s390x/s390-virtio-hcall.c
+++ b/hw/s390x/s390-virtio-hcall.c
@@ -26,11 +26,14 @@ void s390_register_virtio_hypercall(uint64_t code, s390_virtio_fn fn)
 
 int s390_virtio_hypercall(CPUS390XState *env)
 {
-    s390_virtio_fn fn = s390_diag500_table[env->regs[1]];
+    s390_virtio_fn fn;
 
-    if (!fn) {
-        return -EINVAL;
+    if (env->regs[1] < MAX_DIAG_SUBCODES) {
+        fn = s390_diag500_table[env->regs[1]];
+        if (fn) {
+            return fn(&env->regs[2]);
+        }
     }
 
-    return fn(&env->regs[2]);
+    return -EINVAL;
 }
-- 
1.8.4.2