[PATCH v7 1/1] selftests/landlock: skip overlayfs test when kernel not support it

[jeffxu@chromium.org]

From: Jeff Xu <jeffxu@google.com>

Overlayfs can be disabled in kernel config, causing related tests to
fail. Add check for overlayfs’s supportability at runtime,
so we can call SKIP() when needed.

Signed-off-by: Jeff Xu <jeffxu@google.com>
---
 tools/testing/selftests/landlock/fs_test.c | 51 ++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 21a2ce8fa739..34095fe2419b 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -11,6 +11,7 @@
 #include <fcntl.h>
 #include <linux/landlock.h>
 #include <sched.h>
+#include <stdio.h>
 #include <string.h>
 #include <sys/capability.h>
 #include <sys/mount.h>
@@ -62,6 +63,7 @@ static const char dir_s3d1[] = TMP_DIR "/s3d1";
 static const char dir_s3d2[] = TMP_DIR "/s3d1/s3d2";
 static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3";
 
+static const char proc_filesystems[] = "/proc/filesystems";
 /*
  * layout1 hierarchy:
  *
@@ -169,6 +171,43 @@ static int remove_path(const char *const path)
 	return err;
 }
 
+static bool fgrep(FILE *inf, const char *str)
+{
+	char line[32];
+	int slen = strlen(str);
+
+	while (!feof(inf)) {
+		if (!fgets(line, sizeof(line), inf))
+			break;
+		if (strncmp(line, str, slen))
+			continue;
+
+		return true;
+	}
+
+	return false;
+}
+
+static bool supports_overlayfs(void)
+{
+	bool res;
+	FILE *inf = fopen(proc_filesystems, "r");
+
+	/*
+	 * If fopen failed, return supported.
+	 * This help detect missing file (shall not
+	 * happen).
+	 */
+	if (!inf)
+		return true;
+
+	res = fgrep(inf, "nodev\toverlay\n");
+	fclose(inf);
+
+	return res;
+}
+
+
 static void prepare_layout(struct __test_metadata *const _metadata)
 {
 	disable_caps(_metadata);
@@ -3404,6 +3443,9 @@ FIXTURE(layout2_overlay) {};
 
 FIXTURE_SETUP(layout2_overlay)
 {
+	if (!supports_overlayfs())
+		SKIP(return, "overlayfs is not supported");
+
 	prepare_layout(_metadata);
 
 	create_directory(_metadata, LOWER_BASE);
@@ -3440,6 +3482,9 @@ FIXTURE_SETUP(layout2_overlay)
 
 FIXTURE_TEARDOWN(layout2_overlay)
 {
+	if (!supports_overlayfs())
+		SKIP(return, "overlayfs is not supported");
+
 	EXPECT_EQ(0, remove_path(lower_do1_fl3));
 	EXPECT_EQ(0, remove_path(lower_dl1_fl2));
 	EXPECT_EQ(0, remove_path(lower_fl1));
@@ -3471,6 +3516,9 @@ FIXTURE_TEARDOWN(layout2_overlay)
 
 TEST_F_FORK(layout2_overlay, no_restriction)
 {
+	if (!supports_overlayfs())
+		SKIP(return, "overlayfs is not supported");
+
 	ASSERT_EQ(0, test_open(lower_fl1, O_RDONLY));
 	ASSERT_EQ(0, test_open(lower_dl1, O_RDONLY));
 	ASSERT_EQ(0, test_open(lower_dl1_fl2, O_RDONLY));
@@ -3634,6 +3682,9 @@ TEST_F_FORK(layout2_overlay, same_content_different_file)
 	size_t i;
 	const char *path_entry;
 
+	if (!supports_overlayfs())
+		SKIP(return, "overlayfs is not supported");
+
 	/* Sets rules on base directories (i.e. outside overlay scope). */
 	ruleset_fd = create_ruleset(_metadata, ACCESS_RW, layer1_base);
 	ASSERT_LE(0, ruleset_fd);
-- 
2.39.0.314.g84b9a713c41-goog