powerpc/mm/coproc: Handle bad address on coproc slb fault

VSID 0 is bad address. Don't create slb entries on coproc fault for
bad address
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: NBalbir Singh <bsingharora@gmail.com>
Reviewed-by: NIan Munsie <imunsie@au1.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/copro_fault.c

@@ -134,6 +134,9 @@ int copro_calculate_slb(struct mm_struct *mm, u64 ea, struct copro_slb *slb)
 		pr_debug("%s: invalid region access at %016llx\n", __func__, ea);
 		return 1;
 	}
+	/* Bad address */
+	if (!vsid)
+		return 1;
 
 	vsid = (vsid << slb_vsid_shift(ssize)) | vsidkey;