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* Copyright (C) 2010 Karel Zak <kzak@redhat.com>
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* This file may be redistributed under the terms of the
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* GNU Lesser General Public License.
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#include <sys/types.h>
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#ifdef HAVE_LIBSELINUX
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#include <selinux/selinux.h>
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#include <selinux/context.h>
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#include <sys/mount.h>
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* this has to be called after mnt_context_evaluate_permissions()
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static int fix_optstr(struct libmnt_context *cxt)
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int rc = 0, rem_se = 0;
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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DBG(CXT, mnt_debug_h(cxt, "mount: fixing optstr"));
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/* The propagation flags should not be used together with any other flags */
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if (cxt->mountflags & MS_PROPAGATION)
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cxt->mountflags &= MS_PROPAGATION;
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if (!mnt_optstr_get_option(fs->user_optstr, "user", &val, &valsz)) {
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cxt->orig_user = strndup(val, valsz);
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if (!cxt->orig_user) {
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cxt->flags |= MNT_FL_SAVED_USER;
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* Sync mount options with mount flags
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rc = mnt_optstr_apply_flags(&fs->vfs_optstr, cxt->mountflags,
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mnt_get_builtin_optmap(MNT_LINUX_MAP));
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rc = mnt_optstr_apply_flags(&fs->user_optstr, cxt->user_mountflags,
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mnt_get_builtin_optmap(MNT_USERSPACE_MAP));
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#ifdef HAVE_LIBSELINUX
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rem_se = (cxt->mountflags & MS_REMOUNT) || !is_selinux_enabled();
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while (!mnt_optstr_next_option(&next, &name, &namesz, &val, &valsz)) {
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if (namesz == 3 && !strncmp(name, "uid", 3))
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rc = mnt_optstr_fix_uid(&fs->fs_optstr, val, valsz, &next);
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else if (namesz == 3 && !strncmp(name, "gid", 3))
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rc = mnt_optstr_fix_gid(&fs->fs_optstr, val, valsz, &next);
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#ifdef HAVE_LIBSELINUX
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else if (namesz >= 7 && (!strncmp(name, "context", 7) ||
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!strncmp(name, "fscontext", 9) ||
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!strncmp(name, "defcontext", 10) ||
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!strncmp(name, "rootcontext", 11))) {
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/* remove context= option */
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rc = mnt_optstr_remove_option_at(&fs->fs_optstr,
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rc = mnt_optstr_fix_secontext(&fs->fs_optstr,
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if (!rc && cxt->user_mountflags && MNT_MS_USER)
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rc = mnt_optstr_fix_user(&fs->user_optstr);
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DBG(CXT, mnt_debug_h(cxt, "fixed options [rc=%d]: "
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"vfs: '%s' fs: '%s' user: '%s'", rc,
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fs->vfs_optstr, fs->fs_optstr, fs->user_optstr));
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* Converts already evalulated and fixed options to the form that is compatible
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* with /sbin/mount.<type> helpers.
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static int generate_helper_optstr(struct libmnt_context *cxt, char **optstr)
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*optstr = mnt_fs_strdup_options(cxt->fs);
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if (cxt->flags & MNT_FL_SAVED_USER)
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rc = mnt_optstr_set_option(optstr, "user", cxt->orig_user);
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* this has to be called before fix_optstr()
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static int evaluate_permissions(struct libmnt_context *cxt)
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unsigned long u_flags = 0;
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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DBG(CXT, mnt_debug_h(cxt, "mount: evaluating permissions"));
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mnt_context_get_user_mflags(cxt, &u_flags);
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if (!mnt_context_is_restricted(cxt)) {
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cxt->user_mountflags &= ~MNT_MS_OWNER;
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cxt->user_mountflags &= ~MNT_MS_GROUP;
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cxt->user_mountflags &= ~MNT_MS_USER;
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cxt->user_mountflags &= ~MNT_MS_USERS;
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if (!(cxt->flags & MNT_FL_TAB_APPLIED))
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DBG(CXT, mnt_debug_h(cxt, "fstab not applied, ignore user mount"));
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if (u_flags & (MNT_MS_OWNER | MNT_MS_GROUP))
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cxt->mountflags |= MS_OWNERSECURE;
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if (u_flags & (MNT_MS_USER | MNT_MS_USERS))
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cxt->mountflags |= MS_SECURE;
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srcpath = mnt_fs_get_srcpath(cxt->fs);
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* MS_OWNER: Allow owners to mount when fstab contains the
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* owner option. Note that this should never be used in a high
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* security environment, but may be useful to give people at
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* the console the possibility of mounting a floppy. MS_GROUP:
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* Allow members of device group to mount. (Martin Dickopp)
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if (u_flags & (MNT_MS_OWNER | MNT_MS_GROUP)) {
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if (strncmp(srcpath, "/dev/", 5) == 0 &&
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stat(srcpath, &sb) == 0 &&
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(((u_flags & MNT_MS_OWNER) && getuid() == sb.st_uid) ||
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((u_flags & MNT_MS_GROUP) && mnt_in_group(sb.st_gid))))
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cxt->user_mountflags |= MNT_MS_USER;
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if (!(cxt->user_mountflags & (MNT_MS_USER | MNT_MS_USERS))) {
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DBG(CXT, mnt_debug_h(cxt, "permissions evaluation ends with -EPERMS"));
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* mnt_context_helper_setopt() backend
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* This function applies mount.<type> command line option (for example parsed
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* by getopt() or getopt_long()) to @cxt. All unknown options are ignored and
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* then 1 is returned.
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* Returns: negative number on error, 1 if @c is unknown option, 0 on success.
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int mnt_context_mount_setopt(struct libmnt_context *cxt, int c, char *arg)
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assert(cxt->action == MNT_ACT_MOUNT);
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rc = mnt_context_enable_fake(cxt, TRUE);
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rc = mnt_context_disable_mtab(cxt, TRUE);
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rc = mnt_context_append_options(cxt, "ro");
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rc = mnt_context_enable_verbose(cxt, TRUE);
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rc = mnt_context_append_options(cxt, "rw");
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rc = mnt_context_append_options(cxt, arg);
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rc = mnt_context_enable_sloppy(cxt, TRUE);
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rc = mnt_context_set_fstype(cxt, arg);
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static int exec_helper(struct libmnt_context *cxt)
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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DBG(CXT, mnt_debug_h(cxt, "mount: executing helper %s", cxt->helper));
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rc = generate_helper_optstr(cxt, &o);
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const char *args[12], *type;
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if (setgid(getgid()) < 0)
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if (setuid(getuid()) < 0)
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type = mnt_fs_get_fstype(cxt->fs);
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args[i++] = cxt->helper; /* 1 */
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args[i++] = mnt_fs_get_srcpath(cxt->fs);/* 2 */
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args[i++] = mnt_fs_get_target(cxt->fs); /* 3 */
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if (mnt_context_is_sloppy(cxt))
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args[i++] = "-s"; /* 4 */
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if (mnt_context_is_fake(cxt))
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args[i++] = "-f"; /* 5 */
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if (mnt_context_is_nomtab(cxt))
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args[i++] = "-n"; /* 6 */
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if (mnt_context_is_verbose(cxt))
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args[i++] = "-v"; /* 7 */
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args[i++] = "-o"; /* 8 */
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args[i++] = o; /* 9 */
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if (type && !endswith(cxt->helper, type)) {
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args[i++] = "-t"; /* 10 */
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args[i++] = type; /* 11 */
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args[i] = NULL; /* 12 */
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#ifdef CONFIG_LIBMOUNT_DEBUG
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for (i = 0; args[i]; i++)
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DBG(CXT, mnt_debug_h(cxt, "argv[%d] = \"%s\"",
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execv(cxt->helper, (char * const *) args);
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cxt->helper_status = WIFEXITED(st) ? WEXITSTATUS(st) : -1;
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DBG(CXT, mnt_debug_h(cxt, "%s executed [status=%d]",
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cxt->helper, cxt->helper_status));
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cxt->helper_exec_status = rc = 0;
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cxt->helper_exec_status = rc = -errno;
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DBG(CXT, mnt_debug_h(cxt, "fork() failed"));
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* The default is to use fstype from cxt->fs, this could be overwritten by
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* @try_type argument.
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static int do_mount(struct libmnt_context *cxt, const char *try_type)
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const char *src, *target, *type;
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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if (try_type && !cxt->helper) {
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rc = mnt_context_prepare_helper(cxt, "mount", try_type);
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return exec_helper(cxt);
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flags = cxt->mountflags;
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src = mnt_fs_get_srcpath(cxt->fs);
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target = mnt_fs_get_target(cxt->fs);
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type = try_type ? : mnt_fs_get_fstype(cxt->fs);
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if (!(flags & MS_MGC_MSK))
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DBG(CXT, mnt_debug_h(cxt, "%smount(2) "
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"[source=%s, target=%s, type=%s, "
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" mountflags=%08lx, mountdata=%s]",
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(cxt->flags & MNT_FL_FAKE) ? "(FAKE) " : "",
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flags, cxt->mountdata ? "yes" : "<none>"));
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if (cxt->flags & MNT_FL_FAKE)
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cxt->syscall_status = 0;
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if (mount(src, target, type, flags, cxt->mountdata)) {
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cxt->syscall_status = -errno;
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DBG(CXT, mnt_debug_h(cxt, "mount(2) failed [errno=%d %m]",
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-cxt->syscall_status));
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return -cxt->syscall_status;
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DBG(CXT, mnt_debug_h(cxt, "mount(2) success"));
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cxt->syscall_status = 0;
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if (try_type && cxt->update) {
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struct libmnt_fs *fs = mnt_update_get_fs(cxt->update);
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rc = mnt_fs_set_fstype(fs, try_type);
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/* TODO: check if the result is really read-only/read-write
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* and if necessary update cxt->mountflags
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static int do_mount_by_pattern(struct libmnt_context *cxt, const char *pattern)
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int neg = pattern && strncmp(pattern, "no", 2) == 0;
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char **filesystems, **fp;
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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if (!neg && pattern) {
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* try all types from the list
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DBG(CXT, mnt_debug_h(cxt, "tring mount by FS pattern list"));
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p0 = p = strdup(pattern);
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char *end = strchr(p, ',');
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rc = do_mount(cxt, p);
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p = end ? end + 1 : NULL;
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} while (!mnt_context_get_status(cxt) && p);
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if (mnt_context_get_status(cxt))
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* try /etc/filesystems and /proc/filesystems
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DBG(CXT, mnt_debug_h(cxt, "tring mount by filesystems lists"));
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rc = mnt_get_filesystems(&filesystems, neg ? pattern : NULL);
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for (fp = filesystems; *fp; fp++) {
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rc = do_mount(cxt, *fp);
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if (mnt_context_get_status(cxt))
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mnt_free_filesystems(filesystems);
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* mnt_context_prepare_mount:
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* Prepare context for mounting, unnecessary for mnt_context_mount().
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* Returns: negative number on error, zero on success
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int mnt_context_prepare_mount(struct libmnt_context *cxt)
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assert(cxt->helper_exec_status == 1);
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assert(cxt->syscall_status == 1);
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if (!cxt || !cxt->fs || (cxt->fs->flags & MNT_FS_SWAP))
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if (!mnt_fs_get_source(cxt->fs) && !mnt_fs_get_target(cxt->fs))
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if (cxt->flags & MNT_FL_PREPARED)
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cxt->action = MNT_ACT_MOUNT;
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DBG(CXT, mnt_debug_h(cxt, "mount: preparing"));
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/* TODO: fstab is unnecessary for MS_{MOVE,BIND,STARED,...} */
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rc = mnt_context_apply_fstab(cxt);
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rc = mnt_context_merge_mflags(cxt);
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rc = evaluate_permissions(cxt);
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rc = fix_optstr(cxt);
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rc = mnt_context_prepare_srcpath(cxt);
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rc = mnt_context_prepare_target(cxt);
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rc = mnt_context_guess_fstype(cxt);
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rc = mnt_context_prepare_helper(cxt, "mount", NULL);
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DBG(CXT, mnt_debug_h(cxt, "mount: preparing failed"));
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cxt->flags |= MNT_FL_PREPARED;
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* mnt_context_do_mount
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* Call mount(2) or mount.<type> helper. Unnecessary for mnt_context_mount().
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* WARNING: non-zero return code does not mean that mount(2) syscall or
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* umount.type helper wasn't sucessfully called.
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* Check mnt_context_get_status() after error!
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* Returns: 0 on success;
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* >0 in case of mount(2) error (returns syscall errno),
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* <0 in case of other errors.
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int mnt_context_do_mount(struct libmnt_context *cxt)
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assert(cxt->helper_exec_status == 1);
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assert(cxt->syscall_status == 1);
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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assert((cxt->flags & MNT_FL_PREPARED));
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assert((cxt->action == MNT_ACT_MOUNT));
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DBG(CXT, mnt_debug_h(cxt, "mount: do mount"));
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if (!(cxt->flags & MNT_FL_MOUNTDATA))
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cxt->mountdata = (char *) mnt_fs_get_fs_options(cxt->fs);
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type = mnt_fs_get_fstype(cxt->fs);
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return do_mount(cxt, NULL);
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return do_mount_by_pattern(cxt, cxt->fstype_pattern);
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* mnt_context_finalize_mount:
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* Mtab update, etc. Unnecessary for mnt_context_mount(), but should be called
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* after mnt_context_do_mount(). See also mnt_context_set_syscall_status().
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* Returns: negative number on error, 0 on success.
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int mnt_context_finalize_mount(struct libmnt_context *cxt)
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assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
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assert((cxt->flags & MNT_FL_PREPARED));
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rc = mnt_context_prepare_update(cxt);
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rc = mnt_context_update_tabs(cxt);;
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* @cxt: mount context
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* High-level, mounts filesystem by mount(2) or fork()+exec(/sbin/mount.type).
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* This is similar to:
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* mnt_context_prepare_mount(cxt);
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* mnt_context_do_mount(cxt);
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* mnt_context_finalize_mount(cxt);
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* See also mnt_context_disable_helpers().
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* WARNING: non-zero return code does not mean that mount(2) syscall or
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* mount.type helper wasn't sucessfully called.
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* Check mnt_context_get_status() after error!
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* Returns: 0 on success;
610
* >0 in case of mount(2) error (returns syscall errno),
611
* <0 in case of other errors.
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int mnt_context_mount(struct libmnt_context *cxt)
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assert(cxt->helper_exec_status == 1);
620
assert(cxt->syscall_status == 1);
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rc = mnt_context_prepare_mount(cxt);
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rc = mnt_context_prepare_update(cxt);
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rc = mnt_context_do_mount(cxt);
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/* TODO: if mtab update is expected then check if the
629
* target is really mounted read-write to avoid 'ro' in
630
* mtab and 'rw' in /proc/mounts.
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rc = mnt_context_update_tabs(cxt);
added
removed
shlibs/mount/src/context_mount.c
