[PATCH 1/2] selftests/seccomp: Prepare for exclusive seccomp flags

[Kees Cook <keescook@chromium.org>]

Some seccomp flags will become exclusive, so the selftest needs to
be adjusted to mask those out and test them individually for the "all
flags" tests.

Cc: stable@vger.kernel.org # v5.0+
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 tools/testing/selftests/seccomp/seccomp_bpf.c | 34 ++++++++++++++-----
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c
index f69d2ee29742..5019cdae5d0b 100644
--- a/tools/testing/selftests/seccomp/seccomp_bpf.c
+++ b/tools/testing/selftests/seccomp/seccomp_bpf.c
@@ -2166,11 +2166,14 @@ TEST(detect_seccomp_filter_flags)
 				 SECCOMP_FILTER_FLAG_LOG,
 				 SECCOMP_FILTER_FLAG_SPEC_ALLOW,
 				 SECCOMP_FILTER_FLAG_NEW_LISTENER };
-	unsigned int flag, all_flags;
+	unsigned int exclusive[] = {
+				SECCOMP_FILTER_FLAG_TSYNC,
+				SECCOMP_FILTER_FLAG_NEW_LISTENER };
+	unsigned int flag, all_flags, exclusive_mask;
 	int i;
 	long ret;
 
-	/* Test detection of known-good filter flags */
+	/* Test detection of individual known-good filter flags */
 	for (i = 0, all_flags = 0; i < ARRAY_SIZE(flags); i++) {
 		int bits = 0;
 
@@ -2197,16 +2200,29 @@ TEST(detect_seccomp_filter_flags)
 		all_flags |= flag;
 	}
 
-	/* Test detection of all known-good filter flags */
-	ret = seccomp(SECCOMP_SET_MODE_FILTER, all_flags, NULL);
-	EXPECT_EQ(-1, ret);
-	EXPECT_EQ(EFAULT, errno) {
-		TH_LOG("Failed to detect that all known-good filter flags (0x%X) are supported!",
-		       all_flags);
+	/*
+	 * Test detection of all known-good filter flags combined. But
+	 * for the exclusive flags we need to mask them out and try them
+	 * individually for the "all flags" testing.
+	 */
+	exclusive_mask = 0;
+	for (i = 0; i < ARRAY_SIZE(exclusive); i++)
+		exclusive_mask |= exclusive[i];
+	for (i = 0; i < ARRAY_SIZE(exclusive); i++) {
+		flag = all_flags & ~exclusive_mask;
+		flag |= exclusive[i];
+
+		ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);
+		EXPECT_EQ(-1, ret);
+		EXPECT_EQ(EFAULT, errno) {
+			TH_LOG("Failed to detect that all known-good filter flags (0x%X) are supported!",
+			       flag);
+		}
 	}
 
-	/* Test detection of an unknown filter flag */
+	/* Test detection of an unknown filter flags, without exclusives. */
 	flag = -1;
+	flag &= ~exclusive_mask;
 	ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL);
 	EXPECT_EQ(-1, ret);
 	EXPECT_EQ(EINVAL, errno) {
-- 
2.17.1