mountpoint-util: make path_get_mnt_id_at() work with a NULL path

2 files changed, 49 insertions, 3 deletions

diff --git a/src/basic/mountpoint-util.c b/src/basic/mountpoint-util.c
index 7237930a76..3584f31787 100644
--- a/src/basic/mountpoint-util.c
+++ b/src/basic/mountpoint-util.c
@@ -63,7 +63,7 @@ int name_to_handle_at_loop(
 
                 h->handle_bytes = n;
 
-                if (name_to_handle_at(fd, path, h, &mnt_id, flags) >= 0) {
+                if (name_to_handle_at(fd, strempty(path), h, &mnt_id, flags) >= 0) {
 
                         if (ret_handle)
                                 *ret_handle = TAKE_PTR(h);
@@ -362,11 +362,10 @@ int path_get_mnt_id_at(int dir_fd, const char *path, int *ret) {
         int r;
 
         assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
-        assert(path);
         assert(ret);
 
         if (statx(dir_fd,
-                  path,
+                  strempty(path),
                   (isempty(path) ? AT_EMPTY_PATH : AT_SYMLINK_NOFOLLOW) |
                   AT_NO_AUTOMOUNT |    /* don't trigger automounts, mnt_id is a local concept */
                   AT_STATX_DONT_SYNC,  /* don't go to the network, mnt_id is a local concept */
diff --git a/src/test/test-mountpoint-util.c b/src/test/test-mountpoint-util.c
index f5481b5d6b..669b078100 100644
--- a/src/test/test-mountpoint-util.c
+++ b/src/test/test-mountpoint-util.c
@@ -366,6 +366,53 @@ TEST(fstype_can_umask) {
         assert_se(!fstype_can_umask("tmpfs"));
 }
 
+TEST(path_get_mnt_id_at_null) {
+        _cleanup_close_ int root_fd = -EBADF, run_fd = -EBADF;
+        int id1, id2;
+
+        assert_se(path_get_mnt_id_at(AT_FDCWD, "/run/", &id1) >= 0);
+        assert_se(id1 > 0);
+
+        assert_se(path_get_mnt_id_at(AT_FDCWD, "/run", &id2) >= 0);
+        assert_se(id1 == id2);
+        id2 = -1;
+
+        root_fd = open("/", O_DIRECTORY|O_CLOEXEC);
+        assert_se(root_fd >= 0);
+
+        assert_se(path_get_mnt_id_at(root_fd, "/run/", &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+
+        assert_se(path_get_mnt_id_at(root_fd, "/run", &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+
+        assert_se(path_get_mnt_id_at(root_fd, "run", &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+
+        assert_se(path_get_mnt_id_at(root_fd, "run/", &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+
+        run_fd = openat(root_fd, "run", O_DIRECTORY|O_CLOEXEC);
+        assert_se(run_fd >= 0);
+
+        id2 = -1;
+        assert_se(path_get_mnt_id_at(run_fd, "", &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+
+        assert_se(path_get_mnt_id_at(run_fd, NULL, &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+
+        assert_se(path_get_mnt_id_at(run_fd, ".", &id2) >= 0);
+        assert_se(id1 = id2);
+        id2 = -1;
+}
+
 static int intro(void) {
         /* let's move into our own mount namespace with all propagation from the host turned off, so
          * that /proc/self/mountinfo is static and constant for the whole time our test runs. */