[PATCH v1 2/5] selftests/landlock: Fix FS tests when run on a private mount point

["Mickaël Salaün" <mic@digikod.net>]

According to the test environment, the mount point of the test's working
directory may be shared or not, which changes the visibility of the
nested "tmp" mount point for the test's parent process calling
umount("tmp").

This was spotted while running tests on different Linux distributions,
with different mount point configurations.

Cc: Günther Noack <gnoack@google.com>
Fixes: 41cca0542d7c ("selftests/harness: Fix TEST_F()'s vfork handling")
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20240426172252.1862930-3-mic@digikod.net
---
 tools/testing/selftests/landlock/fs_test.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 9a6036fbf289..46b9effd53e4 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -293,7 +293,15 @@ static void prepare_layout(struct __test_metadata *const _metadata)
 static void cleanup_layout(struct __test_metadata *const _metadata)
 {
 	set_cap(_metadata, CAP_SYS_ADMIN);
-	EXPECT_EQ(0, umount(TMP_DIR));
+	if (umount(TMP_DIR)) {
+		/*
+		 * According to the test environment, the mount point of the
+		 * current directory may be shared or not, which changes the
+		 * visibility of the nested TMP_DIR mount point for the test's
+		 * parent process doing this cleanup.
+		 */
+		ASSERT_EQ(EINVAL, errno);
+	}
 	clear_cap(_metadata, CAP_SYS_ADMIN);
 	EXPECT_EQ(0, remove_path(TMP_DIR));
 }
-- 
2.44.0