spapr: Fail CAS if option vector table cannot be parsed

Most of the option vector helpers have assertions to check their
arguments aren't null. The guest can provide an arbitrary address
for the CAS structure that would result in such null arguments.
Fail CAS with H_PARAMETER and print a warning instead of aborting
QEMU.
Signed-off-by: NGreg Kurz <groug@kaod.org>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <157925255250.397143.10855183619366882459.stgit@bahia.lan>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

hw/ppc/spapr_hcall.c

@@ -1703,7 +1703,15 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
     ov_table = addr;
 
     ov1_guest = spapr_ovec_parse_vector(ov_table, 1);
+    if (!ov1_guest) {
+        warn_report("guest didn't provide option vector 1");
+        return H_PARAMETER;
+    }
     ov5_guest = spapr_ovec_parse_vector(ov_table, 5);
+    if (!ov5_guest) {
+        warn_report("guest didn't provide option vector 5");
+        return H_PARAMETER;
+    }
     if (spapr_ovec_test(ov5_guest, OV5_MMU_BOTH)) {
         error_report("guest requested hash and radix MMU, which is invalid.");
         exit(EXIT_FAILURE);