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-rw-r--r--src/shared/mount-util.c570
1 files changed, 570 insertions, 0 deletions
diff --git a/src/shared/mount-util.c b/src/shared/mount-util.c
new file mode 100644
index 0000000..9fa995f
--- /dev/null
+++ b/src/shared/mount-util.c
@@ -0,0 +1,570 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/statvfs.h>
+#include <unistd.h>
+
+/* Include later */
+#include <libmount.h>
+
+#include "alloc-util.h"
+#include "escape.h"
+#include "extract-word.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "hashmap.h"
+#include "mount-util.h"
+#include "mountpoint-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "set.h"
+#include "stdio-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+int umount_recursive(const char *prefix, int flags) {
+ bool again;
+ int n = 0, r;
+
+ /* Try to umount everything recursively below a
+ * directory. Also, take care of stacked mounts, and keep
+ * unmounting them until they are gone. */
+
+ do {
+ _cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
+
+ again = false;
+ r = 0;
+
+ proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
+ if (!proc_self_mountinfo)
+ return -errno;
+
+ (void) __fsetlocking(proc_self_mountinfo, FSETLOCKING_BYCALLER);
+
+ for (;;) {
+ _cleanup_free_ char *path = NULL, *p = NULL;
+ int k;
+
+ k = fscanf(proc_self_mountinfo,
+ "%*s " /* (1) mount id */
+ "%*s " /* (2) parent id */
+ "%*s " /* (3) major:minor */
+ "%*s " /* (4) root */
+ "%ms " /* (5) mount point */
+ "%*s" /* (6) mount options */
+ "%*[^-]" /* (7) optional fields */
+ "- " /* (8) separator */
+ "%*s " /* (9) file system type */
+ "%*s" /* (10) mount source */
+ "%*s" /* (11) mount options 2 */
+ "%*[^\n]", /* some rubbish at the end */
+ &path);
+ if (k != 1) {
+ if (k == EOF)
+ break;
+
+ continue;
+ }
+
+ r = cunescape(path, UNESCAPE_RELAX, &p);
+ if (r < 0)
+ return r;
+
+ if (!path_startswith(p, prefix))
+ continue;
+
+ if (umount2(p, flags) < 0) {
+ r = log_debug_errno(errno, "Failed to umount %s: %m", p);
+ continue;
+ }
+
+ log_debug("Successfully unmounted %s", p);
+
+ again = true;
+ n++;
+
+ break;
+ }
+
+ } while (again);
+
+ return r ? r : n;
+}
+
+static int get_mount_flags(const char *path, unsigned long *flags) {
+ struct statvfs buf;
+
+ if (statvfs(path, &buf) < 0)
+ return -errno;
+ *flags = buf.f_flag;
+ return 0;
+}
+
+/* Use this function only if do you have direct access to /proc/self/mountinfo
+ * and need the caller to open it for you. This is the case when /proc is
+ * masked or not mounted. Otherwise, use bind_remount_recursive. */
+int bind_remount_recursive_with_mountinfo(const char *prefix, bool ro, char **blacklist, FILE *proc_self_mountinfo) {
+ _cleanup_set_free_free_ Set *done = NULL;
+ _cleanup_free_ char *cleaned = NULL;
+ int r;
+
+ assert(proc_self_mountinfo);
+
+ /* Recursively remount a directory (and all its submounts) read-only or read-write. If the directory is already
+ * mounted, we reuse the mount and simply mark it MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
+ * operation). If it isn't we first make it one. Afterwards we apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to
+ * all submounts we can access, too. When mounts are stacked on the same mount point we only care for each
+ * individual "top-level" mount on each point, as we cannot influence/access the underlying mounts anyway. We
+ * do not have any effect on future submounts that might get propagated, they migt be writable. This includes
+ * future submounts that have been triggered via autofs.
+ *
+ * If the "blacklist" parameter is specified it may contain a list of subtrees to exclude from the
+ * remount operation. Note that we'll ignore the blacklist for the top-level path. */
+
+ cleaned = strdup(prefix);
+ if (!cleaned)
+ return -ENOMEM;
+
+ path_simplify(cleaned, false);
+
+ done = set_new(&path_hash_ops);
+ if (!done)
+ return -ENOMEM;
+
+ for (;;) {
+ _cleanup_set_free_free_ Set *todo = NULL;
+ bool top_autofs = false;
+ char *x;
+ unsigned long orig_flags;
+
+ todo = set_new(&path_hash_ops);
+ if (!todo)
+ return -ENOMEM;
+
+ rewind(proc_self_mountinfo);
+
+ for (;;) {
+ _cleanup_free_ char *path = NULL, *p = NULL, *type = NULL;
+ int k;
+
+ k = fscanf(proc_self_mountinfo,
+ "%*s " /* (1) mount id */
+ "%*s " /* (2) parent id */
+ "%*s " /* (3) major:minor */
+ "%*s " /* (4) root */
+ "%ms " /* (5) mount point */
+ "%*s" /* (6) mount options (superblock) */
+ "%*[^-]" /* (7) optional fields */
+ "- " /* (8) separator */
+ "%ms " /* (9) file system type */
+ "%*s" /* (10) mount source */
+ "%*s" /* (11) mount options (bind mount) */
+ "%*[^\n]", /* some rubbish at the end */
+ &path,
+ &type);
+ if (k != 2) {
+ if (k == EOF)
+ break;
+
+ continue;
+ }
+
+ r = cunescape(path, UNESCAPE_RELAX, &p);
+ if (r < 0)
+ return r;
+
+ if (!path_startswith(p, cleaned))
+ continue;
+
+ /* Ignore this mount if it is blacklisted, but only if it isn't the top-level mount we shall
+ * operate on. */
+ if (!path_equal(cleaned, p)) {
+ bool blacklisted = false;
+ char **i;
+
+ STRV_FOREACH(i, blacklist) {
+
+ if (path_equal(*i, cleaned))
+ continue;
+
+ if (!path_startswith(*i, cleaned))
+ continue;
+
+ if (path_startswith(p, *i)) {
+ blacklisted = true;
+ log_debug("Not remounting %s blacklisted by %s, called for %s", p, *i, cleaned);
+ break;
+ }
+ }
+ if (blacklisted)
+ continue;
+ }
+
+ /* Let's ignore autofs mounts. If they aren't
+ * triggered yet, we want to avoid triggering
+ * them, as we don't make any guarantees for
+ * future submounts anyway. If they are
+ * already triggered, then we will find
+ * another entry for this. */
+ if (streq(type, "autofs")) {
+ top_autofs = top_autofs || path_equal(cleaned, p);
+ continue;
+ }
+
+ if (!set_contains(done, p)) {
+ r = set_consume(todo, p);
+ p = NULL;
+ if (r == -EEXIST)
+ continue;
+ if (r < 0)
+ return r;
+ }
+ }
+
+ /* If we have no submounts to process anymore and if
+ * the root is either already done, or an autofs, we
+ * are done */
+ if (set_isempty(todo) &&
+ (top_autofs || set_contains(done, cleaned)))
+ return 0;
+
+ if (!set_contains(done, cleaned) &&
+ !set_contains(todo, cleaned)) {
+ /* The prefix directory itself is not yet a mount, make it one. */
+ if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
+ return -errno;
+
+ orig_flags = 0;
+ (void) get_mount_flags(cleaned, &orig_flags);
+ orig_flags &= ~MS_RDONLY;
+
+ if (mount(NULL, cleaned, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
+ return -errno;
+
+ log_debug("Made top-level directory %s a mount point.", prefix);
+
+ x = strdup(cleaned);
+ if (!x)
+ return -ENOMEM;
+
+ r = set_consume(done, x);
+ if (r < 0)
+ return r;
+ }
+
+ while ((x = set_steal_first(todo))) {
+
+ r = set_consume(done, x);
+ if (IN_SET(r, 0, -EEXIST))
+ continue;
+ if (r < 0)
+ return r;
+
+ /* Deal with mount points that are obstructed by a later mount */
+ r = path_is_mount_point(x, NULL, 0);
+ if (IN_SET(r, 0, -ENOENT))
+ continue;
+ if (IN_SET(r, -EACCES, -EPERM)) {
+ /* Even if root user invoke this, submounts under private FUSE or NFS mount points
+ * may not be acceessed. E.g.,
+ *
+ * $ bindfs --no-allow-other ~/mnt/mnt ~/mnt/mnt
+ * $ bindfs --no-allow-other ~/mnt ~/mnt
+ *
+ * Then, root user cannot access the mount point ~/mnt/mnt.
+ * In such cases, the submounts are ignored, as we have no way to manage them. */
+ log_debug_errno(r, "Failed to determine '%s' is mount point or not, ignoring: %m", x);
+ continue;
+ }
+ if (r < 0)
+ return r;
+
+ /* Try to reuse the original flag set */
+ orig_flags = 0;
+ (void) get_mount_flags(x, &orig_flags);
+ orig_flags &= ~MS_RDONLY;
+
+ if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
+ return -errno;
+
+ log_debug("Remounted %s read-only.", x);
+ }
+ }
+}
+
+int bind_remount_recursive(const char *prefix, bool ro, char **blacklist) {
+ _cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
+
+ proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
+ if (!proc_self_mountinfo)
+ return -errno;
+
+ (void) __fsetlocking(proc_self_mountinfo, FSETLOCKING_BYCALLER);
+
+ return bind_remount_recursive_with_mountinfo(prefix, ro, blacklist, proc_self_mountinfo);
+}
+
+int mount_move_root(const char *path) {
+ assert(path);
+
+ if (chdir(path) < 0)
+ return -errno;
+
+ if (mount(path, "/", NULL, MS_MOVE, NULL) < 0)
+ return -errno;
+
+ if (chroot(".") < 0)
+ return -errno;
+
+ if (chdir("/") < 0)
+ return -errno;
+
+ return 0;
+}
+
+int repeat_unmount(const char *path, int flags) {
+ bool done = false;
+
+ assert(path);
+
+ /* If there are multiple mounts on a mount point, this
+ * removes them all */
+
+ for (;;) {
+ if (umount2(path, flags) < 0) {
+
+ if (errno == EINVAL)
+ return done;
+
+ return -errno;
+ }
+
+ done = true;
+ }
+}
+
+const char* mode_to_inaccessible_node(mode_t mode) {
+ /* This function maps a node type to a corresponding inaccessible file node. These nodes are created during
+ * early boot by PID 1. In some cases we lacked the privs to create the character and block devices (maybe
+ * because we run in an userns environment, or miss CAP_SYS_MKNOD, or run with a devices policy that excludes
+ * device nodes with major and minor of 0), but that's fine, in that case we use an AF_UNIX file node instead,
+ * which is not the same, but close enough for most uses. And most importantly, the kernel allows bind mounts
+ * from socket nodes to any non-directory file nodes, and that's the most important thing that matters. */
+
+ switch(mode & S_IFMT) {
+ case S_IFREG:
+ return "/run/systemd/inaccessible/reg";
+
+ case S_IFDIR:
+ return "/run/systemd/inaccessible/dir";
+
+ case S_IFCHR:
+ if (access("/run/systemd/inaccessible/chr", F_OK) == 0)
+ return "/run/systemd/inaccessible/chr";
+ return "/run/systemd/inaccessible/sock";
+
+ case S_IFBLK:
+ if (access("/run/systemd/inaccessible/blk", F_OK) == 0)
+ return "/run/systemd/inaccessible/blk";
+ return "/run/systemd/inaccessible/sock";
+
+ case S_IFIFO:
+ return "/run/systemd/inaccessible/fifo";
+
+ case S_IFSOCK:
+ return "/run/systemd/inaccessible/sock";
+ }
+ return NULL;
+}
+
+#define FLAG(name) (flags & name ? STRINGIFY(name) "|" : "")
+static char* mount_flags_to_string(long unsigned flags) {
+ char *x;
+ _cleanup_free_ char *y = NULL;
+ long unsigned overflow;
+
+ overflow = flags & ~(MS_RDONLY |
+ MS_NOSUID |
+ MS_NODEV |
+ MS_NOEXEC |
+ MS_SYNCHRONOUS |
+ MS_REMOUNT |
+ MS_MANDLOCK |
+ MS_DIRSYNC |
+ MS_NOATIME |
+ MS_NODIRATIME |
+ MS_BIND |
+ MS_MOVE |
+ MS_REC |
+ MS_SILENT |
+ MS_POSIXACL |
+ MS_UNBINDABLE |
+ MS_PRIVATE |
+ MS_SLAVE |
+ MS_SHARED |
+ MS_RELATIME |
+ MS_KERNMOUNT |
+ MS_I_VERSION |
+ MS_STRICTATIME |
+ MS_LAZYTIME);
+
+ if (flags == 0 || overflow != 0)
+ if (asprintf(&y, "%lx", overflow) < 0)
+ return NULL;
+
+ x = strjoin(FLAG(MS_RDONLY),
+ FLAG(MS_NOSUID),
+ FLAG(MS_NODEV),
+ FLAG(MS_NOEXEC),
+ FLAG(MS_SYNCHRONOUS),
+ FLAG(MS_REMOUNT),
+ FLAG(MS_MANDLOCK),
+ FLAG(MS_DIRSYNC),
+ FLAG(MS_NOATIME),
+ FLAG(MS_NODIRATIME),
+ FLAG(MS_BIND),
+ FLAG(MS_MOVE),
+ FLAG(MS_REC),
+ FLAG(MS_SILENT),
+ FLAG(MS_POSIXACL),
+ FLAG(MS_UNBINDABLE),
+ FLAG(MS_PRIVATE),
+ FLAG(MS_SLAVE),
+ FLAG(MS_SHARED),
+ FLAG(MS_RELATIME),
+ FLAG(MS_KERNMOUNT),
+ FLAG(MS_I_VERSION),
+ FLAG(MS_STRICTATIME),
+ FLAG(MS_LAZYTIME),
+ y);
+ if (!x)
+ return NULL;
+ if (!y)
+ x[strlen(x) - 1] = '\0'; /* truncate the last | */
+ return x;
+}
+
+int mount_verbose(
+ int error_log_level,
+ const char *what,
+ const char *where,
+ const char *type,
+ unsigned long flags,
+ const char *options) {
+
+ _cleanup_free_ char *fl = NULL, *o = NULL;
+ unsigned long f;
+ int r;
+
+ r = mount_option_mangle(options, flags, &f, &o);
+ if (r < 0)
+ return log_full_errno(error_log_level, r,
+ "Failed to mangle mount options %s: %m",
+ strempty(options));
+
+ fl = mount_flags_to_string(f);
+
+ if ((f & MS_REMOUNT) && !what && !type)
+ log_debug("Remounting %s (%s \"%s\")...",
+ where, strnull(fl), strempty(o));
+ else if (!what && !type)
+ log_debug("Mounting %s (%s \"%s\")...",
+ where, strnull(fl), strempty(o));
+ else if ((f & MS_BIND) && !type)
+ log_debug("Bind-mounting %s on %s (%s \"%s\")...",
+ what, where, strnull(fl), strempty(o));
+ else if (f & MS_MOVE)
+ log_debug("Moving mount %s → %s (%s \"%s\")...",
+ what, where, strnull(fl), strempty(o));
+ else
+ log_debug("Mounting %s on %s (%s \"%s\")...",
+ strna(type), where, strnull(fl), strempty(o));
+ if (mount(what, where, type, f, o) < 0)
+ return log_full_errno(error_log_level, errno,
+ "Failed to mount %s (type %s) on %s (%s \"%s\"): %m",
+ strna(what), strna(type), where, strnull(fl), strempty(o));
+ return 0;
+}
+
+int umount_verbose(const char *what) {
+ log_debug("Umounting %s...", what);
+ if (umount(what) < 0)
+ return log_error_errno(errno, "Failed to unmount %s: %m", what);
+ return 0;
+}
+
+int mount_option_mangle(
+ const char *options,
+ unsigned long mount_flags,
+ unsigned long *ret_mount_flags,
+ char **ret_remaining_options) {
+
+ const struct libmnt_optmap *map;
+ _cleanup_free_ char *ret = NULL;
+ const char *p;
+ int r;
+
+ /* This extracts mount flags from the mount options, and store
+ * non-mount-flag options to '*ret_remaining_options'.
+ * E.g.,
+ * "rw,nosuid,nodev,relatime,size=1630748k,mode=700,uid=1000,gid=1000"
+ * is split to MS_NOSUID|MS_NODEV|MS_RELATIME and
+ * "size=1630748k,mode=700,uid=1000,gid=1000".
+ * See more examples in test-mount-utils.c.
+ *
+ * Note that if 'options' does not contain any non-mount-flag options,
+ * then '*ret_remaining_options' is set to NULL instread of empty string.
+ * Note that this does not check validity of options stored in
+ * '*ret_remaining_options'.
+ * Note that if 'options' is NULL, then this just copies 'mount_flags'
+ * to '*ret_mount_flags'. */
+
+ assert(ret_mount_flags);
+ assert(ret_remaining_options);
+
+ map = mnt_get_builtin_optmap(MNT_LINUX_MAP);
+ if (!map)
+ return -EINVAL;
+
+ p = options;
+ for (;;) {
+ _cleanup_free_ char *word = NULL;
+ const struct libmnt_optmap *ent;
+
+ r = extract_first_word(&p, &word, ",", EXTRACT_QUOTES);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ break;
+
+ for (ent = map; ent->name; ent++) {
+ /* All entries in MNT_LINUX_MAP do not take any argument.
+ * Thus, ent->name does not contain "=" or "[=]". */
+ if (!streq(word, ent->name))
+ continue;
+
+ if (!(ent->mask & MNT_INVERT))
+ mount_flags |= ent->id;
+ else if (mount_flags & ent->id)
+ mount_flags ^= ent->id;
+
+ break;
+ }
+
+ /* If 'word' is not a mount flag, then store it in '*ret_remaining_options'. */
+ if (!ent->name && !strextend_with_separator(&ret, ",", word, NULL))
+ return -ENOMEM;
+ }
+
+ *ret_mount_flags = mount_flags;
+ *ret_remaining_options = TAKE_PTR(ret);
+
+ return 0;
+}
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