selftests: KVM: Check stat name before other fields

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2119111



commit ad5b0727
Author: Oliver Upton <oupton@google.com>
Date:   Tue Jul 19 14:31:32 2022 +0000

    selftests: KVM: Check stat name before other fields

    In order to provide more useful test assertions that describe the broken
    stats descriptor, perform sanity check on the stat name before any other
    descriptor field. While at it, avoid dereferencing the name field if the
    sanity check fails as it is more likely to contain garbage.

Signed-off-by: Oliver Upton <oupton@google.com>
Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
    Message-Id: <20220719143134.3246798-2-oliver.upton@linux.dev>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>

tools/testing/selftests/kvm/kvm_binary_stats_test.c

@@ -73,6 +73,10 @@ static void stats_test(int stats_fd)
 	for (i = 0; i < header.num_desc; ++i) {
 		pdesc = get_stats_descriptor(stats_desc, i, &header);
 
+		/* Check name string */
+		TEST_ASSERT(strlen(pdesc->name) < header.name_size,
+			    "KVM stats name (index: %d) too long", i);
+
 		/* Check type,unit,base boundaries */
 		TEST_ASSERT((pdesc->flags & KVM_STATS_TYPE_MASK) <= KVM_STATS_TYPE_MAX,
 			    "Unknown KVM stats type");
@@ -99,9 +103,7 @@ static void stats_test(int stats_fd)
 			TEST_ASSERT(pdesc->exponent <= 0, "Unsupported KVM stats unit");
 			break;
 		}
-		/* Check name string */
-		TEST_ASSERT(strlen(pdesc->name) < header.name_size,
-			    "KVM stats name(%s) too long", pdesc->name);
+
 		/* Check size field, which should not be zero */
 		TEST_ASSERT(pdesc->size,
 			    "KVM descriptor(%s) with size of 0", pdesc->name);