Move mount-util.c to shared/

libmount dep is moved from libbasic to libshared, potentially removing
libmount from some build products.

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 0000000000..9fa995f693
--- /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;
+}