Test SIOCGSKNS fails on non-socket file descriptors.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 .../testing/selftests/namespaces/siocgskns_test.c  | 26 ++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/tools/testing/selftests/namespaces/siocgskns_test.c b/tools/testing/selftests/namespaces/siocgskns_test.c
index 28e45954c4fa..bbfef3c51ac1 100644
--- a/tools/testing/selftests/namespaces/siocgskns_test.c
+++ b/tools/testing/selftests/namespaces/siocgskns_test.c
@@ -307,4 +307,30 @@ TEST(siocgskns_across_setns)
 	close(netns_a_fd);
 }
 
+/*
+ * Test SIOCGSKNS fails on non-socket file descriptors.
+ */
+TEST(siocgskns_non_socket)
+{
+	int fd;
+	int pipefd[2];
+
+	/* Test on regular file */
+	fd = open("/dev/null", O_RDONLY);
+	ASSERT_GE(fd, 0);
+
+	ASSERT_LT(ioctl(fd, SIOCGSKNS), 0);
+	ASSERT_TRUE(errno == ENOTTY || errno == EINVAL);
+	close(fd);
+
+	/* Test on pipe */
+	ASSERT_EQ(pipe(pipefd), 0);
+
+	ASSERT_LT(ioctl(pipefd[0], SIOCGSKNS), 0);
+	ASSERT_TRUE(errno == ENOTTY || errno == EINVAL);
+
+	close(pipefd[0]);
+	close(pipefd[1]);
+}
+
 TEST_HARNESS_MAIN

-- 
2.47.3