mount-util: make path_get_mount_info() work arbitrary inode

Follow-up for d49d95df0a.
Replaces 9a032ec55a.
Fixes #35075.

TODO

@@ -129,6 +129,10 @@ Deprecations and removals:
 
 Features:
 
+* format-table: introduce new cell type for strings with ansi sequences in
+  them. display them in regular output mode (via strip_tab_ansi()), but
+  suppress them in json mode.
+
 * machined: when registering a machine, also take a relative cgroup path,
   relative to the machine's unit. This is useful when registering unpriv
   machines, as they might sit down the cgroup tree, below a cgroup delegation
@@ -217,12 +221,8 @@ Features:
   services where mount propagation from the root fs is off, an still have
   confext/sysext propagated in.
 
-* support F_DUDFD_QUERY for comparing fds in same_fd (requires kernel 6.10)
-
 * generic interface for varlink for setting log level and stuff that all our daemons can implement
 
-* use pty ioctl to get peer wherever possible (TIOCGPTPEER)
-
 * maybe teach repart.d/ dropins a new setting MakeMountNodes= or so, which is
   just like MakeDirectories=, but uses an access mode of 0000 and sets the +i
   chattr bit. This is useful as protection against early uses of /var/ or /tmp/
@@ -253,8 +253,6 @@ Features:
 * initrd: when transitioning from initrd to host, validate that
   /lib/modules/`uname -r` exists, refuse otherwise
 
-* tmpfiles: add "owning" flag for lines that limits effect of --purge
-
 * signed bpf loading: to address need for signature verification for bpf
   programs when they are loaded, and given the bpf folks don't think this is
   realistic in kernel space, maybe add small daemon that facilitates this
@@ -458,9 +456,6 @@ Features:
 * introduce mntid_t, and make it 64bit, as apparently the kernel switched to
   64bit mount ids
 
-* use udev rule networkd ownership property to take ownership of network
-  interfaces nspawn creates
-
 * mountfsd/nsresourced
   - userdb: maybe allow callers to map one uid to their own uid
   - bpflsm: allow writes if resulting UID on disk would be userns' owner UID
@@ -647,6 +642,7 @@ Features:
   - openpt_allocate_in_namespace()
   - unit_attach_pid_to_cgroup_via_bus()
   - cg_attach() – requires new kernel feature
+  - journald's process cache
 
 * ddi must be listed as block device fstype
 
@@ -1470,9 +1466,6 @@ Features:
 
 * in sd-id128: also parse UUIDs in RFC4122 URN syntax (i.e. chop off urn:uuid: prefix)
 
-* DynamicUser= + StateDirectory= → use uid mapping mounts, too, in order to
-  make dirs appear under right UID.
-
 * systemd-sysext: optionally, run it in initrd already, before transitioning
   into host, to open up possibility for services shipped like that.
 
@@ -1644,14 +1637,6 @@ Features:
 
 * maybe add kernel cmdline params: to force random seed crediting
 
-* introduce a new per-process uuid, similar to the boot id, the machine id, the
-  invocation id, that is derived from process creds, specifically a hashed
-  combination of AT_RANDOM + getpid() + the starttime from
-  /proc/self/status. Then add these ids implicitly when logging. Deriving this
-  uuid from these three things has the benefit that it can be derived easily
-  from /proc/$PID/ in a stable, and unique way that changes on both fork() and
-  exec().
-
 * let's not GC a unit while its ratelimits are still pending
 
 * when killing due to service watchdog timeout maybe detect whether target

src/basic/fs-util.c

@@ -1131,6 +1131,8 @@ int xopenat_full(int dir_fd, const char *path, int open_flags, XOpenFlags xopen_
          *   • If O_CREAT is used with XO_LABEL, any created file will be immediately relabelled.
          *
          *   • If the path is specified NULL or empty, behaves like fd_reopen().
+         *
+         *   • If XO_NOCOW is specified will turn on the NOCOW btrfs flag on the file, if available.
          */
 
         if (isempty(path)) {

src/shared/mount-util.c

@@ -1808,40 +1808,50 @@ char* umount_and_unlink_and_free(char *p) {
         return mfree(p);
 }
 
-static int path_get_mount_info(
+static int path_get_mount_info_at(
+                int dir_fd,
                 const char *path,
                 char **ret_fstype,
                 char **ret_options) {
 
         _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL;
-        _cleanup_free_ char *fstype = NULL, *options = NULL;
-        struct libmnt_fs *fs;
-        int r;
+        _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL;
+        int r, mnt_id;
 
-        assert(path);
+        assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
 
-        table = mnt_new_table();
-        if (!table)
-                return -ENOMEM;
-
-        r = mnt_table_parse_mtab(table, /* filename = */ NULL);
+        r = path_get_mnt_id_at(dir_fd, path, &mnt_id);
         if (r < 0)
-                return r;
+                return log_debug_errno(r, "Failed to get mount ID: %m");
 
-        fs = mnt_table_find_mountpoint(table, path, MNT_ITER_FORWARD);
-        if (!fs)
-                return -EINVAL;
+        r = libmount_parse("/proc/self/mountinfo", NULL, &table, &iter);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to parse /proc/self/mountinfo: %m");
+
+        for (;;) {
+                struct libmnt_fs *fs;
+
+                r = mnt_table_next_fs(table, iter, &fs);
+                if (r == 1)
+                        break; /* EOF */
+                if (r < 0)
+                        return log_debug_errno(r, "Failed to get next entry from /proc/self/mountinfo: %m");
+
+                if (mnt_fs_get_id(fs) != mnt_id)
+                        continue;
+
+                _cleanup_free_ char *fstype = NULL, *options = NULL;
 
                 if (ret_fstype) {
                         fstype = strdup(strempty(mnt_fs_get_fstype(fs)));
                         if (!fstype)
-                        return -ENOMEM;
+                                return log_oom_debug();
                 }
 
                 if (ret_options) {
                         options = strdup(strempty(mnt_fs_get_options(fs)));
                         if (!options)
-                        return -ENOMEM;
+                                return log_oom_debug();
                 }
 
                 if (ret_fstype)
@@ -1852,19 +1862,27 @@ static int path_get_mount_info(
                 return 0;
         }
 
-int path_is_network_fs_harder(const char *path) {
+        return log_debug_errno(SYNTHETIC_ERRNO(ESTALE), "Cannot find mount ID %i from /proc/self/mountinfo.", mnt_id);
+}
+
+int path_is_network_fs_harder_at(int dir_fd, const char *path) {
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
+
+        fd = xopenat(dir_fd, path, O_PATH | O_CLOEXEC | O_NOFOLLOW);
+        if (fd < 0)
+                return fd;
+
+        r = fd_is_network_fs(fd);
+        if (r != 0)
+                return r;
+
         _cleanup_free_ char *fstype = NULL, *options = NULL;
-        int r, ret;
-
-        assert(path);
-
-        ret = path_is_network_fs(path);
-        if (ret > 0)
-                return true;
-
-        r = path_get_mount_info(path, &fstype, &options);
+        r = path_get_mount_info_at(fd, /* path = */ NULL, &fstype, &options);
         if (r < 0)
-                return RET_GATHER(ret, r);
+                return r;
 
         if (fstype_is_network(fstype))
                 return true;

src/shared/mount-util.h

@@ -181,4 +181,7 @@ int mount_credentials_fs(const char *path, size_t size, bool ro);
 
 int make_fsmount(int error_log_level, const char *what, const char *type, unsigned long flags, const char *options, int userns_fd);
 
-int path_is_network_fs_harder(const char *path);
+int path_is_network_fs_harder_at(int dir_fd, const char *path);
+static inline int path_is_network_fs_harder(const char *path) {
+        return path_is_network_fs_harder_at(AT_FDCWD, path);
+}

src/test/test-mount-util.c

@@ -538,9 +538,53 @@ TEST(bind_mount_submounts) {
 }
 
 TEST(path_is_network_fs_harder) {
-        ASSERT_OK_ZERO(path_is_network_fs_harder("/dev"));
-        ASSERT_OK_ZERO(path_is_network_fs_harder("/sys"));
-        ASSERT_OK_ZERO(path_is_network_fs_harder("/run"));
+        _cleanup_close_ int dir_fd = -EBADF;
+        int r;
+
+        ASSERT_OK(dir_fd = open("/", O_PATH | O_CLOEXEC));
+        FOREACH_STRING(s,
+                       "/", "/dev/", "/proc/", "/run/", "/sys/", "/tmp/", "/usr/", "/var/tmp/",
+                       "", ".", "../../../", "/this/path/should/not/exist/for/test-mount-util/") {
+
+                r = path_is_network_fs_harder(s);
+                log_debug("path_is_network_fs_harder(%s) → %i: %s", s, r, r < 0 ? STRERROR(r) : yes_no(r));
+
+                const char *q = path_startswith(s, "/") ?: s;
+                r = path_is_network_fs_harder_at(dir_fd, q);
+                log_debug("path_is_network_fs_harder_at(root, %s) → %i: %s", q, r, r < 0 ? STRERROR(r) : yes_no(r));
+        }
+
+        if (geteuid() != 0 || have_effective_cap(CAP_SYS_ADMIN) <= 0) {
+                (void) log_tests_skipped("not running privileged");
+                return;
+        }
+
+        _cleanup_(rm_rf_physical_and_freep) char *t = NULL;
+        assert_se(mkdtemp_malloc("/tmp/test-mount-util.path_is_network_fs_harder.XXXXXXX", &t) >= 0);
+
+        r = safe_fork("(make_mount-point)",
+                      FORK_RESET_SIGNALS |
+                      FORK_CLOSE_ALL_FDS |
+                      FORK_DEATHSIG_SIGTERM |
+                      FORK_WAIT |
+                      FORK_REOPEN_LOG |
+                      FORK_LOG |
+                      FORK_NEW_MOUNTNS |
+                      FORK_MOUNTNS_SLAVE,
+                      NULL);
+        ASSERT_OK(r);
+
+        if (r == 0) {
+                ASSERT_OK(mount_nofollow_verbose(LOG_INFO, "tmpfs", t, "tmpfs", 0, NULL));
+                ASSERT_OK_ZERO(path_is_network_fs_harder(t));
+                ASSERT_OK_ERRNO(umount(t));
+
+                ASSERT_OK(mount_nofollow_verbose(LOG_INFO, "tmpfs", t, "tmpfs", 0, "x-systemd-growfs,x-systemd-automount"));
+                ASSERT_OK_ZERO(path_is_network_fs_harder(t));
+                ASSERT_OK_ERRNO(umount(t));
+
+                _exit(EXIT_SUCCESS);
+        }
 }
 
 DEFINE_TEST_MAIN(LOG_DEBUG);

test/meson.build

@@ -142,11 +142,13 @@ endif
 ############################################################
 
 if install_tests
-        foreach script : ['integration-test-setup.sh', 'run-unit-tests.py']
-                install_data(script,
+        install_data('run-unit-tests.py',
                      install_mode : 'rwxr-xr-x',
                      install_dir : testsdir)
-        endforeach
+
+        install_data('integration-test-setup.sh',
+                     install_mode : 'rwxr-xr-x',
+                     install_dir : testdata_dir)
 endif
 
 ############################################################

test/test.service.in

@@ -7,9 +7,9 @@ Before=getty-pre.target
 
 [Service]
 ExecStartPre=rm -f /failed /testok
-ExecStartPre=/usr/lib/systemd/tests/integration-test-setup.sh setup
+ExecStartPre=/usr/lib/systemd/tests/testdata/integration-test-setup.sh setup
 ExecStart=@command@
-ExecStopPost=/usr/lib/systemd/tests/integration-test-setup.sh finalize
+ExecStopPost=/usr/lib/systemd/tests/testdata/integration-test-setup.sh finalize
 Type=oneshot
 MemoryAccounting=@memory-accounting@
 StateDirectory=%N