/* SPDX-License-Identifier: LGPL-2.1-or-later */ /*** Copyright © 2010 ProFUSION embedded systems ***/ #include <errno.h> #include <fcntl.h> #include <sys/mount.h> #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> #include "alloc-util.h" #include "chase.h" #include "dirent-util.h" #include "fd-util.h" #include "fileio.h" #include "fs-util.h" #include "fstab-util.h" #include "libmount-util.h" #include "mkdir.h" #include "mount-setup.h" #include "mount-util.h" #include "mountpoint-util.h" #include "parse-util.h" #include "process-util.h" #include "random-util.h" #include "signal-util.h" #include "umount.h" #include "virt.h" static void mount_point_free(MountPoint **head, MountPoint *m) { assert(head); assert(m); LIST_REMOVE(mount_point, *head, m); free(m->path); free(m->remount_options); free(m); } void mount_points_list_free(MountPoint **head) { assert(head); while (*head) mount_point_free(head, *head); } int mount_points_list_get(const char *mountinfo, MountPoint **head) { _cleanup_(mnt_free_tablep) struct libmnt_table *table = NULL; _cleanup_(mnt_free_iterp) struct libmnt_iter *iter = NULL; int r; assert(head); r = libmount_parse(mountinfo, NULL, &table, &iter); if (r < 0) return log_error_errno(r, "Failed to parse %s: %m", mountinfo ?: "/proc/self/mountinfo"); for (;;) { _cleanup_free_ char *options = NULL, *remount_options = NULL; struct libmnt_fs *fs; const char *path, *fstype; unsigned long remount_flags = 0u; bool try_remount_ro, is_api_vfs; _cleanup_free_ MountPoint *m = NULL; r = mnt_table_next_fs(table, iter, &fs); if (r == 1) /* EOF */ break; if (r < 0) return log_error_errno(r, "Failed to get next entry from %s: %m", mountinfo ?: "/proc/self/mountinfo"); path = mnt_fs_get_target(fs); if (!path) continue; fstype = mnt_fs_get_fstype(fs); /* Combine the generic VFS options with the FS-specific options. Duplicates are not a problem * here, because the only options that should come up twice are typically ro/rw, which are * turned into MS_RDONLY or the inversion of it. * * Even if there are duplicates later in mount_option_mangle() they shouldn't hurt anyways as * they override each other. */ if (!strextend_with_separator(&options, ",", mnt_fs_get_vfs_options(fs))) return log_oom(); if (!strextend_with_separator(&options, ",", mnt_fs_get_fs_options(fs))) return log_oom(); /* Ignore mount points we can't unmount because they are API or because we are keeping them * open (like /dev/console). Also, ignore all mounts below API file systems, since they are * likely virtual too, and hence not worth spending time on. Also, in unprivileged containers * we might lack the rights to unmount these things, hence don't bother. */ if (mount_point_is_api(path) || mount_point_ignore(path) || path_below_api_vfs(path)) continue; is_api_vfs = fstype_is_api_vfs(fstype); /* If we are in a container, don't attempt to read-only mount anything as that brings no real * benefits, but might confuse the host, as we remount the superblock here, not the bind * mount. * * If the filesystem is a network fs, also skip the remount. It brings no value (we cannot * leave a "dirty fs") and could hang if the network is down. Note that umount2() is more * careful and will not hang because of the network being down. */ try_remount_ro = detect_container() <= 0 && !fstype_is_network(fstype) && !is_api_vfs && !fstype_is_ro(fstype) && !fstab_test_yes_no_option(options, "ro\0rw\0"); if (try_remount_ro) { /* mount(2) states that mount flags and options need to be exactly the same as they * were when the filesystem was mounted, except for the desired changes. So we * reconstruct both here and adjust them for the later remount call too. */ r = mnt_fs_get_propagation(fs, &remount_flags); if (r < 0) { log_warning_errno(r, "mnt_fs_get_propagation() failed for %s, ignoring: %m", path); continue; } r = mount_option_mangle(options, remount_flags, &remount_flags, &remount_options); if (r < 0) { log_warning_errno(r, "mount_option_mangle failed for %s, ignoring: %m", path); continue; } /* MS_BIND is special. If it is provided it will only make the mount-point * read-only. If left out, the super block itself is remounted, which we want. */ remount_flags = (remount_flags|MS_REMOUNT|MS_RDONLY) & ~MS_BIND; } m = new(MountPoint, 1); if (!m) return log_oom(); r = libmount_is_leaf(table, fs); if (r < 0) return log_error_errno(r, "Failed to get children mounts for %s from %s: %m", path, mountinfo ?: "/proc/self/mountinfo"); bool leaf = r; *m = (MountPoint) { .remount_options = remount_options, .remount_flags = remount_flags, .try_remount_ro = try_remount_ro, /* Unmount sysfs/procfs/… lazily, since syncing doesn't matter there, and it's OK if * something keeps an fd open to it. */ .umount_lazily = is_api_vfs, .leaf = leaf, }; m->path = strdup(path); if (!m->path) return log_oom(); TAKE_PTR(remount_options); LIST_PREPEND(mount_point, *head, TAKE_PTR(m)); } return 0; } static bool nonunmountable_path(const char *path) { assert(path); return PATH_IN_SET(path, "/", "/usr") || path_startswith(path, "/run/initramfs"); } static void log_umount_blockers(const char *mnt) { _cleanup_free_ char *blockers = NULL; int r; _cleanup_closedir_ DIR *dir = opendir("/proc"); if (!dir) return (void) log_warning_errno(errno, "Failed to open /proc/: %m"); FOREACH_DIRENT_ALL(de, dir, break) { if (!IN_SET(de->d_type, DT_DIR, DT_UNKNOWN)) continue; pid_t pid; if (parse_pid(de->d_name, &pid) < 0) continue; _cleanup_free_ char *fdp = path_join(de->d_name, "fd"); if (!fdp) return (void) log_oom(); _cleanup_closedir_ DIR *fd_dir = xopendirat(dirfd(dir), fdp, 0); if (!fd_dir) { if (errno != ENOENT) /* process gone by now? */ log_debug_errno(errno, "Failed to open /proc/%s/, ignoring: %m",fdp); continue; } bool culprit = false; FOREACH_DIRENT(fd_de, fd_dir, break) { _cleanup_free_ char *open_file = NULL; r = readlinkat_malloc(dirfd(fd_dir), fd_de->d_name, &open_file); if (r < 0) { if (r != -ENOENT) /* fd closed by now */ log_debug_errno(r, "Failed to read link /proc/%s/%s, ignoring: %m", fdp, fd_de->d_name); continue; } if (path_startswith(open_file, mnt)) { culprit = true; break; } } if (!culprit) continue; _cleanup_free_ char *comm = NULL; r = pid_get_comm(pid, &comm); if (r < 0) { if (r != -ESRCH) /* process gone by now */ log_debug_errno(r, "Failed to read process name of PID " PID_FMT ": %m", pid); continue; } if (!strextend_with_separator(&blockers, ", ", comm)) return (void) log_oom(); if (!strextend(&blockers, "(", de->d_name, ")")) return (void) log_oom(); } if (blockers) log_warning("Unmounting '%s' blocked by: %s", mnt, blockers); } static int remount_with_timeout(MountPoint *m, bool last_try) { _cleanup_close_pair_ int pfd[2] = EBADF_PAIR; _cleanup_(sigkill_nowaitp) pid_t pid = 0; int r; BLOCK_SIGNALS(SIGCHLD); assert(m); r = pipe2(pfd, O_CLOEXEC|O_NONBLOCK); if (r < 0) return r; /* Due to the possibility of a remount operation hanging, we fork a child process and set a * timeout. If the timeout lapses, the assumption is that the particular remount failed. */ r = safe_fork_full("(sd-remount)", NULL, pfd, ELEMENTSOF(pfd), FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_LOG|FORK_REOPEN_LOG, &pid); if (r < 0) return r; if (r == 0) { pfd[0] = safe_close(pfd[0]); log_info("Remounting '%s' read-only with options '%s'.", m->path, strempty(m->remount_options)); /* Start the mount operation here in the child */ r = mount(NULL, m->path, NULL, m->remount_flags, m->remount_options); if (r < 0) log_full_errno(last_try ? LOG_ERR : LOG_INFO, errno, "Failed to remount '%s' read-only: %m", m->path); (void) write(pfd[1], &r, sizeof(r)); /* try to send errno up */ _exit(r < 0 ? EXIT_FAILURE : EXIT_SUCCESS); } pfd[1] = safe_close(pfd[1]); r = wait_for_terminate_with_timeout(pid, DEFAULT_TIMEOUT_USEC); if (r == -ETIMEDOUT) log_error_errno(r, "Remounting '%s' timed out, issuing SIGKILL to PID " PID_FMT ".", m->path, pid); else if (r == -EPROTO) { /* Try to read error code from child */ if (read(pfd[0], &r, sizeof(r)) == sizeof(r)) log_debug_errno(r, "Remounting '%s' failed abnormally, child process " PID_FMT " failed: %m", m->path, pid); else r = log_debug_errno(EPROTO, "Remounting '%s' failed abnormally, child process " PID_FMT " aborted or exited non-zero.", m->path, pid); TAKE_PID(pid); /* child exited (just not as we expected) hence don't kill anymore */ } else if (r < 0) log_error_errno(r, "Remounting '%s' failed unexpectedly, couldn't wait for child process " PID_FMT ": %m", m->path, pid); return r; } static int umount_with_timeout(MountPoint *m, bool last_try) { _cleanup_close_pair_ int pfd[2] = EBADF_PAIR; _cleanup_(sigkill_nowaitp) pid_t pid = 0; int r; BLOCK_SIGNALS(SIGCHLD); assert(m); r = pipe2(pfd, O_CLOEXEC|O_NONBLOCK); if (r < 0) return r; /* Due to the possibility of a umount operation hanging, we fork a child process and set a * timeout. If the timeout lapses, the assumption is that the particular umount failed. */ r = safe_fork_full("(sd-umount)", NULL, pfd, ELEMENTSOF(pfd), FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_LOG|FORK_REOPEN_LOG, &pid); if (r < 0) return r; if (r == 0) { pfd[0] = safe_close(pfd[0]); log_info("Unmounting '%s'.", m->path); /* Start the mount operation here in the child Using MNT_FORCE causes some filesystems * (e.g. FUSE and NFS and other network filesystems) to abort any pending requests and return * -EIO rather than blocking indefinitely. If the filesysten is "busy", this may allow * processes to die, thus making the filesystem less busy so the unmount might succeed * (rather than return EBUSY). */ r = RET_NERRNO(umount2(m->path, UMOUNT_NOFOLLOW | /* Don't follow symlinks: this should never happen unless our mount list was wrong */ (m->umount_lazily ? MNT_DETACH : MNT_FORCE))); if (r < 0) { log_full_errno(last_try ? LOG_ERR : LOG_INFO, r, "Failed to unmount %s: %m", m->path); if (r == -EBUSY && last_try) log_umount_blockers(m->path); } (void) write(pfd[1], &r, sizeof(r)); /* try to send errno up */ _exit(r < 0 ? EXIT_FAILURE : EXIT_SUCCESS); } pfd[1] = safe_close(pfd[1]); r = wait_for_terminate_with_timeout(pid, DEFAULT_TIMEOUT_USEC); if (r == -ETIMEDOUT) log_error_errno(r, "Unmounting '%s' timed out, issuing SIGKILL to PID " PID_FMT ".", m->path, pid); else if (r == -EPROTO) { /* Try to read error code from child */ if (read(pfd[0], &r, sizeof(r)) == sizeof(r)) log_debug_errno(r, "Unmounting '%s' failed abnormally, child process " PID_FMT " failed: %m", m->path, pid); else r = log_debug_errno(EPROTO, "Unmounting '%s' failed abnormally, child process " PID_FMT " aborted or exited non-zero.", m->path, pid); TAKE_PID(pid); /* It died, but abnormally, no purpose in killing */ } else if (r < 0) log_error_errno(r, "Unmounting '%s' failed unexpectedly, couldn't wait for child process " PID_FMT ": %m", m->path, pid); return r; } /* This includes remounting readonly, which changes the kernel mount options. Therefore the list passed to * this function is invalidated, and should not be reused. */ static int mount_points_list_umount(MountPoint **head, bool *changed, bool last_try) { int n_failed = 0, r; _cleanup_free_ char *resolved_mounts_path = NULL; assert(head); assert(changed); LIST_FOREACH(mount_point, m, *head) { if (m->try_remount_ro) { /* We always try to remount directories read-only first, before we go on and umount * them. * * Mount points can be stacked. If a mount point is stacked below / or /usr, we * cannot umount or remount it directly, since there is no way to refer to the * underlying mount. There's nothing we can do about it for the general case, but we * can do something about it if it is aliased somewhere else via a bind mount. If we * explicitly remount the super block of that alias read-only we hence should be * relatively safe regarding keeping a dirty fs we cannot otherwise see. * * Since the remount can hang in the instance of remote filesystems, we remount * asynchronously and skip the subsequent umount if it fails. */ if (remount_with_timeout(m, last_try) < 0) { /* Remount failed, but try unmounting anyway, * unless this is a mount point we want to skip. */ if (nonunmountable_path(m->path)) { n_failed++; continue; } } } /* Skip / and /usr since we cannot unmount that anyway, since we are running from it. They * have already been remounted ro. */ if (nonunmountable_path(m->path)) continue; /* Trying to umount */ r = umount_with_timeout(m, last_try); if (r < 0) n_failed++; else *changed = true; /* If a mount is busy, we move it to not keep parent mount points busy. * If a mount point is not a leaf, moving it would invalidate our mount table. * More moving will occur in next iteration with a fresh mount table. */ if (r != -EBUSY || !m->leaf) continue; _cleanup_free_ char *dirname = NULL; r = path_extract_directory(m->path, &dirname); if (r < 0) { n_failed++; log_full_errno(last_try ? LOG_ERR : LOG_INFO, r, "Cannot find directory for %s: %m", m->path); continue; } /* We need to canonicalize /run/shutdown/mounts. We cannot compare inodes, since /run * might be bind mounted somewhere we want to unmount. And we need to move all mounts in * /run/shutdown/mounts from there. */ if (!resolved_mounts_path) (void) chase("/run/shutdown/mounts", NULL, 0, &resolved_mounts_path, NULL); if (!path_equal(dirname, resolved_mounts_path)) { char newpath[STRLEN("/run/shutdown/mounts/") + 16 + 1]; xsprintf(newpath, "/run/shutdown/mounts/%016" PRIx64, random_u64()); /* on error of is_dir, assume directory */ if (is_dir(m->path, true) != 0) { r = mkdir_p(newpath, 0000); if (r < 0) { log_full_errno(last_try ? LOG_ERR : LOG_INFO, r, "Could not create directory %s: %m", newpath); continue; } } else { r = touch_file(newpath, /* parents= */ true, USEC_INFINITY, UID_INVALID, GID_INVALID, 0700); if (r < 0) { log_full_errno(last_try ? LOG_ERR : LOG_INFO, r, "Could not create file %s: %m", newpath); continue; } } log_info("Moving mount %s to %s.", m->path, newpath); r = RET_NERRNO(mount(m->path, newpath, NULL, MS_MOVE, NULL)); if (r < 0) { n_failed++; log_full_errno(last_try ? LOG_ERR : LOG_INFO, r, "Could not move %s to %s: %m", m->path, newpath); } else *changed = true; } } return n_failed; } static int umount_all_once(bool *changed, bool last_try) { _cleanup_(mount_points_list_free) LIST_HEAD(MountPoint, mp_list_head); int r; assert(changed); LIST_HEAD_INIT(mp_list_head); r = mount_points_list_get(NULL, &mp_list_head); if (r < 0) return r; return mount_points_list_umount(&mp_list_head, changed, last_try); } int umount_all(bool *changed, bool last_try) { bool umount_changed; int r; assert(changed); /* Retry umount, until nothing can be umounted anymore. Mounts are processed in order, newest * first. The retries are needed when an old mount has been moved, to a path inside a newer mount. */ do { umount_changed = false; r = umount_all_once(&umount_changed, last_try); if (umount_changed) *changed = true; } while (umount_changed); return r; }