selftests/namespaces: fourth listns() test

Test listns() with LISTNS_CURRENT_USER.
List namespaces owned by current user namespace.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-42-2e6f823ebdc0@kernel.org
Tested-by: syzbot@syzkaller.appspotmail.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/namespaces/listns_test.c b/tools/testing/selftests/namespaces/listns_test.c
index 7dff63a00263b663b8e295ee96c0c0a59840bcf5..457298cb4c64ad944df134ae7528a4b531c1d5c4 100644 (file)
--- a/tools/testing/selftests/namespaces/listns_test.c
+++ b/tools/testing/selftests/namespaces/listns_test.c
@@ -168,4 +168,37 @@ TEST(listns_pagination)
        }
 }
 
+/*
+ * Test listns() with LISTNS_CURRENT_USER.
+ * List namespaces owned by current user namespace.
+ */
+TEST(listns_current_user)
+{
+       struct ns_id_req req = {
+               .size = sizeof(req),
+               .spare = 0,
+               .ns_id = 0,
+               .ns_type = 0,
+               .spare2 = 0,
+               .user_ns_id = LISTNS_CURRENT_USER,
+       };
+       __u64 ns_ids[100];
+       ssize_t ret;
+
+       ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
+       if (ret < 0) {
+               if (errno == ENOSYS)
+                       SKIP(return, "listns() not supported");
+               TH_LOG("listns failed: %s (errno=%d)", strerror(errno), errno);
+               ASSERT_TRUE(false);
+       }
+       ASSERT_GE(ret, 0);
+
+       /* Should find at least the initial namespaces if we're in init_user_ns */
+       TH_LOG("Found %zd namespaces owned by current user namespace", ret);
+
+       for (ssize_t i = 0; i < ret; i++)
+               TH_LOG("  [%zd] ns_id: %llu", i, (unsigned long long)ns_ids[i]);
+}
+
 TEST_HARNESS_MAIN