selftests/namespaces: sixth listns() test

Test listns() with specific user namespace ID.
Create a user namespace and list namespaces it owns.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-44-2e6f823ebdc0@kernel.org
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 a04ebe11ce2ce0d0512b2877e398b8d163d4e5fe..f5b8bc5d111f200a8ee009e59f0c2db5da420fe5 100644 (file)
--- a/tools/testing/selftests/namespaces/listns_test.c
+++ b/tools/testing/selftests/namespaces/listns_test.c
@@ -9,6 +9,7 @@
 #include <string.h>
 #include <linux/nsfs.h>
 #include <sys/ioctl.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
@@ -324,4 +325,125 @@ TEST(listns_only_active)
        }
 }
 
+/*
+ * Test listns() with specific user namespace ID.
+ * Create a user namespace and list namespaces it owns.
+ */
+TEST(listns_specific_userns)
+{
+       struct ns_id_req req = {
+               .size = sizeof(req),
+               .spare = 0,
+               .ns_id = 0,
+               .ns_type = 0,
+               .spare2 = 0,
+               .user_ns_id = 0,  /* Will be filled with created userns ID */
+       };
+       __u64 ns_ids[100];
+       int sv[2];
+       pid_t pid;
+       int status;
+       __u64 user_ns_id = 0;
+       int bytes;
+       ssize_t ret;
+
+       ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM, 0, sv), 0);
+
+       pid = fork();
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0) {
+               int fd;
+               __u64 ns_id;
+               char buf;
+
+               close(sv[0]);
+
+               /* Create new user namespace */
+               if (setup_userns() < 0) {
+                       close(sv[1]);
+                       exit(1);
+               }
+
+               /* Get user namespace ID */
+               fd = open("/proc/self/ns/user", O_RDONLY);
+               if (fd < 0) {
+                       close(sv[1]);
+                       exit(1);
+               }
+
+               if (ioctl(fd, NS_GET_ID, &ns_id) < 0) {
+                       close(fd);
+                       close(sv[1]);
+                       exit(1);
+               }
+               close(fd);
+
+               /* Send ID to parent */
+               if (write(sv[1], &ns_id, sizeof(ns_id)) != sizeof(ns_id)) {
+                       close(sv[1]);
+                       exit(1);
+               }
+
+               /* Create some namespaces owned by this user namespace */
+               unshare(CLONE_NEWNET);
+               unshare(CLONE_NEWUTS);
+
+               /* Wait for parent signal */
+               if (read(sv[1], &buf, 1) != 1) {
+                       close(sv[1]);
+                       exit(1);
+               }
+               close(sv[1]);
+               exit(0);
+       }
+
+       /* Parent */
+       close(sv[1]);
+       bytes = read(sv[0], &user_ns_id, sizeof(user_ns_id));
+
+       if (bytes != sizeof(user_ns_id)) {
+               close(sv[0]);
+               kill(pid, SIGKILL);
+               waitpid(pid, NULL, 0);
+               SKIP(return, "Failed to get user namespace ID from child");
+       }
+
+       TH_LOG("Child created user namespace with ID %llu", (unsigned long long)user_ns_id);
+
+       /* List namespaces owned by this user namespace */
+       req.user_ns_id = user_ns_id;
+       ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
+
+       if (ret < 0) {
+               TH_LOG("listns failed: %s (errno=%d)", strerror(errno), errno);
+               close(sv[0]);
+               kill(pid, SIGKILL);
+               waitpid(pid, NULL, 0);
+               if (errno == ENOSYS) {
+                       SKIP(return, "listns() not supported");
+               }
+               ASSERT_GE(ret, 0);
+       }
+
+       TH_LOG("Found %zd namespaces owned by user namespace %llu", ret,
+              (unsigned long long)user_ns_id);
+
+       /* Should find at least the network and UTS namespaces we created */
+       if (ret > 0) {
+               for (ssize_t i = 0; i < ret && i < 10; i++)
+                       TH_LOG("  [%zd] ns_id: %llu", i, (unsigned long long)ns_ids[i]);
+       }
+
+       /* Signal child to exit */
+       if (write(sv[0], "X", 1) != 1) {
+               close(sv[0]);
+               kill(pid, SIGKILL);
+               waitpid(pid, NULL, 0);
+               ASSERT_TRUE(false);
+       }
+       close(sv[0]);
+       waitpid(pid, &status, 0);
+}
+
 TEST_HARNESS_MAIN