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context_umount.c
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context_umount.c
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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* This file is part of libmount from util-linux project.
*
* Copyright (C) 2010-2018 Karel Zak <kzak@redhat.com>
*
* libmount is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*/
/**
* SECTION: context-umount
* @title: Umount context
* @short_description: high-level API to umount operation.
*/
#include <sys/wait.h>
#include <sys/mount.h>
#include "pathnames.h"
#include "loopdev.h"
#include "strutils.h"
#include "mountP.h"
/*
* umount2 flags
*/
#ifndef MNT_FORCE
# define MNT_FORCE 0x00000001 /* Attempt to forcibly umount */
#endif
#ifndef MNT_DETACH
# define MNT_DETACH 0x00000002 /* Just detach from the tree */
#endif
#ifndef UMOUNT_NOFOLLOW
# define UMOUNT_NOFOLLOW 0x00000008 /* Don't follow symlink on umount */
#endif
#ifndef UMOUNT_UNUSED
# define UMOUNT_UNUSED 0x80000000 /* Flag guaranteed to be unused */
#endif
/* search in mountinfo/mtab */
static int __mtab_find_umount_fs(struct libmnt_context *cxt,
const char *tgt,
struct libmnt_fs **pfs)
{
int rc;
struct libmnt_ns *ns_old;
struct libmnt_table *mtab = NULL;
struct libmnt_fs *fs;
char *loopdev = NULL;
assert(cxt);
assert(tgt);
assert(pfs);
*pfs = NULL;
DBG(CXT, ul_debugobj(cxt, " search %s in mountinfo", tgt));
/*
* The mount table may be huge, and on systems with utab we have to
* merge userspace mount options into /proc/self/mountinfo. This all is
* expensive. The tab filter can be used to filter out entries, then a mount
* table and utab are very tiny files.
*
* The filter uses mnt_fs_streq_{target,srcpath} function where all
* paths should be absolute and canonicalized. This is done within
* mnt_context_get_mtab_for_target() where LABEL, UUID or symlinks are
* canonicalized. If --no-canonicalize is enabled than the target path
* is expected already canonical.
*
* Anyway it's better to read huge mount table than canonicalize target
* paths. It means we use the filter only if --no-canonicalize enabled.
*
* It also means that we have to read mount table from kernel
* (non-writable mtab).
*/
if (mnt_context_is_nocanonicalize(cxt) &&
!mnt_context_mtab_writable(cxt) && *tgt == '/')
rc = mnt_context_get_mtab_for_target(cxt, &mtab, tgt);
else
rc = mnt_context_get_mtab(cxt, &mtab);
if (rc) {
DBG(CXT, ul_debugobj(cxt, "umount: failed to read mtab"));
return rc;
}
if (mnt_table_get_nents(mtab) == 0) {
DBG(CXT, ul_debugobj(cxt, "umount: mtab empty"));
return 1;
}
ns_old = mnt_context_switch_target_ns(cxt);
if (!ns_old)
return -MNT_ERR_NAMESPACE;
try_loopdev:
fs = mnt_table_find_target(mtab, tgt, MNT_ITER_BACKWARD);
if (!fs && mnt_context_is_swapmatch(cxt)) {
/*
* Maybe the option is source rather than target (sometimes
* people use e.g. "umount /dev/sda1")
*/
fs = mnt_table_find_source(mtab, tgt, MNT_ITER_BACKWARD);
if (fs) {
struct libmnt_fs *fs1 = mnt_table_find_target(mtab,
mnt_fs_get_target(fs),
MNT_ITER_BACKWARD);
if (!fs1) {
DBG(CXT, ul_debugobj(cxt, "mtab is broken?!?!"));
rc = -EINVAL;
goto err;
}
if (fs != fs1) {
/* Something was stacked over `file' on the
* same mount point. */
DBG(CXT, ul_debugobj(cxt,
"umount: %s: %s is mounted "
"over it on the same point",
tgt, mnt_fs_get_source(fs1)));
rc = -EINVAL;
goto err;
}
}
}
if (!fs && !loopdev && mnt_context_is_swapmatch(cxt)) {
/*
* Maybe the option is /path/file.img, try to convert to /dev/loopN
*/
struct stat st;
if (mnt_stat_mountpoint(tgt, &st) == 0 && S_ISREG(st.st_mode)) {
int count;
struct libmnt_cache *cache = mnt_context_get_cache(cxt);
const char *bf = cache ? mnt_resolve_path(tgt, cache) : tgt;
count = loopdev_count_by_backing_file(bf, &loopdev);
if (count == 1) {
DBG(CXT, ul_debugobj(cxt,
"umount: %s --> %s (retry)", tgt, loopdev));
tgt = loopdev;
goto try_loopdev;
} else if (count > 1)
DBG(CXT, ul_debugobj(cxt,
"umount: warning: %s is associated "
"with more than one loopdev", tgt));
}
}
*pfs = fs;
free(loopdev);
if (!mnt_context_switch_ns(cxt, ns_old))
return -MNT_ERR_NAMESPACE;
DBG(CXT, ul_debugobj(cxt, "umount fs: %s", fs ? mnt_fs_get_target(fs) :
"<not found>"));
return fs ? 0 : 1;
err:
free(loopdev);
if (!mnt_context_switch_ns(cxt, ns_old))
return -MNT_ERR_NAMESPACE;
return rc;
}
/**
* mnt_context_find_umount_fs:
* @cxt: mount context
* @tgt: mountpoint, device, ...
* @pfs: returns point to filesystem
*
* Returns: 0 on success, <0 on error, 1 if target filesystem not found
*/
int mnt_context_find_umount_fs(struct libmnt_context *cxt,
const char *tgt,
struct libmnt_fs **pfs)
{
if (pfs)
*pfs = NULL;
if (!cxt || !tgt || !pfs)
return -EINVAL;
DBG(CXT, ul_debugobj(cxt, "umount: lookup FS for '%s'", tgt));
if (!*tgt)
return 1; /* empty string is not an error */
/* In future this function should be extended to support for example
* fsinfo() (or another cheap way kernel will support), for now the
* default is expensive mountinfo/mtab.
*/
return __mtab_find_umount_fs(cxt, tgt, pfs);
}
/* Check if there is something important in the utab file. The parsed utab is
* stored in context->utab and deallocated by mnt_free_context().
*
* This function exists to avoid (if possible) /proc/self/mountinfo usage, so
* don't use things like mnt_resolve_target(), mnt_context_get_mtab() etc here.
* See lookup_umount_fs() for more details.
*/
static int has_utab_entry(struct libmnt_context *cxt, const char *target)
{
struct libmnt_cache *cache = NULL;
struct libmnt_fs *fs;
struct libmnt_iter itr;
char *cn = NULL;
int rc = 0;
assert(cxt);
if (!cxt->utab) {
const char *path = mnt_get_utab_path();
if (!path || is_file_empty(path))
return 0;
cxt->utab = mnt_new_table();
if (!cxt->utab)
return 0;
cxt->utab->fmt = MNT_FMT_UTAB;
if (mnt_table_parse_file(cxt->utab, path))
return 0;
}
/* paths in utab are canonicalized */
cache = mnt_context_get_cache(cxt);
cn = mnt_resolve_path(target, cache);
mnt_reset_iter(&itr, MNT_ITER_BACKWARD);
while (mnt_table_next_fs(cxt->utab, &itr, &fs) == 0) {
if (mnt_fs_streq_target(fs, cn)) {
rc = 1;
break;
}
}
if (!cache)
free(cn);
return rc;
}
/* returns: 1 not found; <0 on error; 1 success */
static int lookup_umount_fs_by_statfs(struct libmnt_context *cxt, const char *tgt)
{
struct stat st;
const char *type;
DBG(CXT, ul_debugobj(cxt, " lookup by statfs"));
/*
* Let's try to avoid mountinfo usage at all to minimize performance
* degradation. Don't forget that kernel has to compose *whole*
* mountinfo about all mountpoints although we look for only one entry.
*
* All we need is fstype and to check if there is no userspace mount
* options for the target (e.g. helper=udisks to call /sbin/umount.udisks).
*
* So, let's use statfs() if possible (it's bad idea for --lazy/--force
* umounts as target is probably unreachable NFS, also for --detach-loop
* as this additionally needs to know the name of the loop device).
*/
if (mnt_context_is_restricted(cxt)
|| *tgt != '/'
|| (cxt->flags & MNT_FL_HELPER)
|| mnt_context_mtab_writable(cxt)
|| mnt_context_is_force(cxt)
|| mnt_context_is_lazy(cxt)
|| mnt_context_is_nocanonicalize(cxt)
|| mnt_context_is_loopdel(cxt)
|| mnt_stat_mountpoint(tgt, &st) != 0 || !S_ISDIR(st.st_mode)
|| has_utab_entry(cxt, tgt))
return 1; /* not found */
type = mnt_fs_get_fstype(cxt->fs);
DBG(CXT, ul_debugobj(cxt, " umount: disabling mtab"));
mnt_context_disable_mtab(cxt, TRUE);
if (!type) {
struct statfs vfs;
int fd;
DBG(CXT, ul_debugobj(cxt, " trying fstatfs()"));
/* O_PATH avoids triggering automount points. */
fd = open(tgt, O_PATH);
if (fd >= 0) {
if (fstatfs(fd, &vfs) == 0)
type = mnt_statfs_get_fstype(&vfs);
close(fd);
}
if (type) {
int rc = mnt_fs_set_fstype(cxt->fs, type);
if (rc)
return rc;
}
}
if (type) {
DBG(CXT, ul_debugobj(cxt,
" mountinfo unnecessary [type=%s]", type));
return 0;
}
return 1; /* not found */
}
/* returns: 1 not found; <0 on error; 1 success */
static int lookup_umount_fs_by_mountinfo(struct libmnt_context *cxt, const char *tgt)
{
struct libmnt_fs *fs = NULL;
int rc;
DBG(CXT, ul_debugobj(cxt, " lookup by mountinfo"));
/* search */
rc = __mtab_find_umount_fs(cxt, tgt, &fs);
if (rc != 0)
return rc;
/* apply result */
if (fs != cxt->fs) {
mnt_fs_set_source(cxt->fs, NULL);
mnt_fs_set_target(cxt->fs, NULL);
if (!mnt_copy_fs(cxt->fs, fs)) {
DBG(CXT, ul_debugobj(cxt, " failed to copy FS"));
return -errno;
}
DBG(CXT, ul_debugobj(cxt, " mtab applied"));
}
cxt->flags |= MNT_FL_TAB_APPLIED;
return 0;
}
/* This finction search for FS according to cxt->fs->target,
* apply result to cxt->fs and it's umount replacement to
* mnt_context_apply_fstab(), use mnt_context_tab_applied()
* to check result.
*
* The goal is to minimize situations when we need to parse
* /proc/self/mountinfo.
*/
static int lookup_umount_fs(struct libmnt_context *cxt)
{
const char *tgt;
int rc = 0;
assert(cxt);
assert(cxt->fs);
DBG(CXT, ul_debugobj(cxt, "umount: lookup FS"));
tgt = mnt_fs_get_target(cxt->fs);
if (!tgt) {
DBG(CXT, ul_debugobj(cxt, " undefined target"));
return -EINVAL;
}
/* try get fs type by statfs() */
rc = lookup_umount_fs_by_statfs(cxt, tgt);
if (rc <= 0)
return rc;
/* get complete fs from fs entry from mountinfo */
rc = lookup_umount_fs_by_mountinfo(cxt, tgt);
if (rc <= 0)
return rc;
DBG(CXT, ul_debugobj(cxt, " cannot find '%s'", tgt));
return 0; /* this is correct! */
}
/* check if @devname is loopdev and if the device is associated
* with a source from @fstab_fs
*/
static int is_associated_fs(const char *devname, struct libmnt_fs *fs)
{
uintmax_t offset = 0;
const char *src, *optstr;
char *val;
size_t valsz;
int flags = 0;
/* check if it begins with /dev/loop */
if (strncmp(devname, _PATH_DEV_LOOP, sizeof(_PATH_DEV_LOOP) - 1) != 0)
return 0;
src = mnt_fs_get_srcpath(fs);
if (!src)
return 0;
/* check for the offset option in @fs */
optstr = mnt_fs_get_user_options(fs);
if (optstr &&
mnt_optstr_get_option(optstr, "offset", &val, &valsz) == 0) {
flags |= LOOPDEV_FL_OFFSET;
if (mnt_parse_offset(val, valsz, &offset) != 0)
return 0;
}
return loopdev_is_used(devname, src, offset, 0, flags);
}
static int prepare_helper_from_options(struct libmnt_context *cxt,
const char *name)
{
char *suffix = NULL;
const char *opts;
size_t valsz;
int rc;
if (mnt_context_is_nohelpers(cxt))
return 0;
opts = mnt_fs_get_user_options(cxt->fs);
if (!opts)
return 0;
if (mnt_optstr_get_option(opts, name, &suffix, &valsz))
return 0;
suffix = strndup(suffix, valsz);
if (!suffix)
return -ENOMEM;
DBG(CXT, ul_debugobj(cxt, "umount: umount.%s %s requested", suffix, name));
rc = mnt_context_prepare_helper(cxt, "umount", suffix);
free(suffix);
return rc;
}
static int is_fuse_usermount(struct libmnt_context *cxt, int *errsv)
{
struct libmnt_ns *ns_old;
const char *type = mnt_fs_get_fstype(cxt->fs);
const char *optstr;
char *user_id = NULL;
size_t sz;
uid_t uid;
char uidstr[sizeof(stringify_value(ULONG_MAX))];
*errsv = 0;
if (!type)
return 0;
if (strcmp(type, "fuse") != 0 &&
strcmp(type, "fuseblk") != 0 &&
strncmp(type, "fuse.", 5) != 0 &&
strncmp(type, "fuseblk.", 8) != 0)
return 0;
/* get user_id= from mount table */
optstr = mnt_fs_get_fs_options(cxt->fs);
if (!optstr)
return 0;
if (mnt_optstr_get_option(optstr, "user_id", &user_id, &sz) != 0)
return 0;
if (sz == 0 || user_id == NULL)
return 0;
/* get current user */
ns_old = mnt_context_switch_origin_ns(cxt);
if (!ns_old) {
*errsv = -MNT_ERR_NAMESPACE;
return 0;
}
uid = getuid();
if (!mnt_context_switch_ns(cxt, ns_old)) {
*errsv = -MNT_ERR_NAMESPACE;
return 0;
}
snprintf(uidstr, sizeof(uidstr), "%lu", (unsigned long) uid);
return strncmp(user_id, uidstr, sz) == 0;
}
/*
* Note that cxt->fs contains relevant mtab entry!
*/
static int evaluate_permissions(struct libmnt_context *cxt)
{
struct libmnt_table *fstab;
unsigned long u_flags = 0;
const char *tgt, *src, *optstr;
int rc = 0, ok = 0;
struct libmnt_fs *fs;
assert(cxt);
assert(cxt->fs);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
if (!mnt_context_is_restricted(cxt))
return 0; /* superuser mount */
DBG(CXT, ul_debugobj(cxt, "umount: evaluating permissions"));
if (!mnt_context_tab_applied(cxt)) {
DBG(CXT, ul_debugobj(cxt,
"cannot find %s in mtab and you are not root",
mnt_fs_get_target(cxt->fs)));
goto eperm;
}
if (cxt->user_mountflags & MNT_MS_UHELPER) {
/* on uhelper= mount option based helper */
rc = prepare_helper_from_options(cxt, "uhelper");
if (rc)
return rc;
if (cxt->helper)
return 0; /* we'll call /sbin/umount.<uhelper> */
}
/*
* Check if this is a fuse mount for the current user,
* if so then unmounting is allowed
*/
if (is_fuse_usermount(cxt, &rc)) {
DBG(CXT, ul_debugobj(cxt, "fuse user mount, umount is allowed"));
return 0;
}
if (rc)
return rc;
/*
* User mounts have to be in /etc/fstab
*/
rc = mnt_context_get_fstab(cxt, &fstab);
if (rc)
return rc;
tgt = mnt_fs_get_target(cxt->fs);
src = mnt_fs_get_source(cxt->fs);
if (mnt_fs_get_bindsrc(cxt->fs)) {
src = mnt_fs_get_bindsrc(cxt->fs);
DBG(CXT, ul_debugobj(cxt,
"umount: using bind source: %s", src));
}
/* If fstab contains the two lines
* /dev/sda1 /mnt/zip auto user,noauto 0 0
* /dev/sda4 /mnt/zip auto user,noauto 0 0
* then "mount /dev/sda4" followed by "umount /mnt/zip" used to fail.
* So, we must not look for the file, but for the pair (dev,file) in fstab.
*/
fs = mnt_table_find_pair(fstab, src, tgt, MNT_ITER_FORWARD);
if (!fs) {
/*
* It's possible that there is /path/file.img in fstab and
* /dev/loop0 in mtab -- then we have to check the relation
* between loopdev and the file.
*/
fs = mnt_table_find_target(fstab, tgt, MNT_ITER_FORWARD);
if (fs) {
struct libmnt_cache *cache = mnt_context_get_cache(cxt);
const char *sp = mnt_fs_get_srcpath(cxt->fs); /* devname from mtab */
const char *dev = sp && cache ? mnt_resolve_path(sp, cache) : sp;
if (!dev || !is_associated_fs(dev, fs))
fs = NULL;
}
if (!fs) {
DBG(CXT, ul_debugobj(cxt,
"umount %s: mtab disagrees with fstab",
tgt));
goto eperm;
}
}
/*
* User mounting and unmounting is allowed only if fstab contains one
* of the options `user', `users' or `owner' or `group'.
*
* The option `users' allows arbitrary users to mount and unmount -
* this may be a security risk.
*
* The options `user', `owner' and `group' only allow unmounting by the
* user that mounted (visible in mtab).
*/
optstr = mnt_fs_get_user_options(fs); /* FSTAB mount options! */
if (!optstr)
goto eperm;
if (mnt_optstr_get_flags(optstr, &u_flags,
mnt_get_builtin_optmap(MNT_USERSPACE_MAP)))
goto eperm;
if (u_flags & MNT_MS_USERS) {
DBG(CXT, ul_debugobj(cxt,
"umount: promiscuous setting ('users') in fstab"));
return 0;
}
/*
* Check user=<username> setting from mtab if there is a user, owner or
* group option in /etc/fstab
*/
if (u_flags & (MNT_MS_USER | MNT_MS_OWNER | MNT_MS_GROUP)) {
char *curr_user;
char *mtab_user = NULL;
size_t sz;
struct libmnt_ns *ns_old;
DBG(CXT, ul_debugobj(cxt,
"umount: checking user=<username> from mtab"));
ns_old = mnt_context_switch_origin_ns(cxt);
if (!ns_old)
return -MNT_ERR_NAMESPACE;
curr_user = mnt_get_username(getuid());
if (!mnt_context_switch_ns(cxt, ns_old)) {
free(curr_user);
return -MNT_ERR_NAMESPACE;
}
if (!curr_user) {
DBG(CXT, ul_debugobj(cxt, "umount %s: cannot "
"convert %d to username", tgt, getuid()));
goto eperm;
}
/* get options from mtab */
optstr = mnt_fs_get_user_options(cxt->fs);
if (optstr && !mnt_optstr_get_option(optstr,
"user", &mtab_user, &sz) && sz)
ok = !strncmp(curr_user, mtab_user, sz);
free(curr_user);
}
if (ok) {
DBG(CXT, ul_debugobj(cxt, "umount %s is allowed", tgt));
return 0;
}
eperm:
DBG(CXT, ul_debugobj(cxt, "umount is not allowed for you"));
return -EPERM;
}
static int exec_helper(struct libmnt_context *cxt)
{
char *namespace = NULL;
struct libmnt_ns *ns_tgt = mnt_context_get_target_ns(cxt);
int rc;
pid_t pid;
assert(cxt);
assert(cxt->fs);
assert(cxt->helper);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
assert(cxt->helper_exec_status == 1);
if (mnt_context_is_fake(cxt)) {
DBG(CXT, ul_debugobj(cxt, "fake mode: does not execute helper"));
cxt->helper_exec_status = rc = 0;
return rc;
}
if (ns_tgt->fd != -1
&& asprintf(&namespace, "/proc/%i/fd/%i",
getpid(), ns_tgt->fd) == -1) {
return -ENOMEM;
}
DBG_FLUSH;
pid = fork();
switch (pid) {
case 0:
{
const char *args[12], *type;
int i = 0;
if (setgid(getgid()) < 0)
_exit(EXIT_FAILURE);
if (setuid(getuid()) < 0)
_exit(EXIT_FAILURE);
if (!mnt_context_switch_origin_ns(cxt))
_exit(EXIT_FAILURE);
type = mnt_fs_get_fstype(cxt->fs);
args[i++] = cxt->helper; /* 1 */
args[i++] = mnt_fs_get_target(cxt->fs); /* 2 */
if (mnt_context_is_nomtab(cxt))
args[i++] = "-n"; /* 3 */
if (mnt_context_is_lazy(cxt))
args[i++] = "-l"; /* 4 */
if (mnt_context_is_force(cxt))
args[i++] = "-f"; /* 5 */
if (mnt_context_is_verbose(cxt))
args[i++] = "-v"; /* 6 */
if (mnt_context_is_rdonly_umount(cxt))
args[i++] = "-r"; /* 7 */
if (type
&& strchr(type, '.')
&& !endswith(cxt->helper, type)) {
args[i++] = "-t"; /* 8 */
args[i++] = type; /* 9 */
}
if (namespace) {
args[i++] = "-N"; /* 10 */
args[i++] = namespace; /* 11 */
}
args[i] = NULL; /* 12 */
for (i = 0; args[i]; i++)
DBG(CXT, ul_debugobj(cxt, "argv[%d] = \"%s\"",
i, args[i]));
DBG_FLUSH;
execv(cxt->helper, (char * const *) args);
_exit(EXIT_FAILURE);
}
default:
{
int st;
if (waitpid(pid, &st, 0) == (pid_t) -1) {
cxt->helper_status = -1;
rc = -errno;
} else {
cxt->helper_status = WIFEXITED(st) ? WEXITSTATUS(st) : -1;
cxt->helper_exec_status = rc = 0;
}
DBG(CXT, ul_debugobj(cxt, "%s executed [status=%d, rc=%d%s]",
cxt->helper,
cxt->helper_status, rc,
rc ? " waitpid failed" : ""));
break;
}
case -1:
cxt->helper_exec_status = rc = -errno;
DBG(CXT, ul_debugobj(cxt, "fork() failed"));
break;
}
return rc;
}
/*
* mnt_context_helper_setopt() backend.
*
* This function applies umount.type command line option (for example parsed
* by getopt() or getopt_long()) to @cxt. All unknown options are ignored and
* then 1 is returned.
*
* Returns: negative number on error, 1 if @c is unknown option, 0 on success.
*/
int mnt_context_umount_setopt(struct libmnt_context *cxt, int c, char *arg)
{
int rc = -EINVAL;
assert(cxt);
assert(cxt->action == MNT_ACT_UMOUNT);
switch(c) {
case 'n':
rc = mnt_context_disable_mtab(cxt, TRUE);
break;
case 'l':
rc = mnt_context_enable_lazy(cxt, TRUE);
break;
case 'f':
rc = mnt_context_enable_force(cxt, TRUE);
break;
case 'v':
rc = mnt_context_enable_verbose(cxt, TRUE);
break;
case 'r':
rc = mnt_context_enable_rdonly_umount(cxt, TRUE);
break;
case 't':
if (arg)
rc = mnt_context_set_fstype(cxt, arg);
break;
case 'N':
if (arg)
rc = mnt_context_set_target_ns(cxt, arg);
break;
default:
return 1;
}
return rc;
}
/* Check whether the kernel supports the UMOUNT_NOFOLLOW flag */
static int umount_nofollow_support(void)
{
int res = umount2("", UMOUNT_UNUSED);
if (res != -1 || errno != EINVAL)
return 0;
res = umount2("", UMOUNT_NOFOLLOW);
if (res != -1 || errno != ENOENT)
return 0;
return 1;
}
static int do_umount(struct libmnt_context *cxt)
{
int rc = 0, flags = 0;
const char *src, *target;
char *tgtbuf = NULL;
assert(cxt);
assert(cxt->fs);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
assert(cxt->syscall_status == 1);
if (cxt->helper)
return exec_helper(cxt);
src = mnt_fs_get_srcpath(cxt->fs);
target = mnt_fs_get_target(cxt->fs);
if (!target)
return -EINVAL;
DBG(CXT, ul_debugobj(cxt, "do umount"));
if (mnt_context_is_restricted(cxt) && !mnt_context_is_fake(cxt)) {
/*
* extra paranoia for non-root users
* -- chdir to the parent of the mountpoint and use NOFOLLOW
* flag to avoid races and symlink attacks.
*/
if (umount_nofollow_support())
flags |= UMOUNT_NOFOLLOW;
rc = mnt_chdir_to_parent(target, &tgtbuf);
if (rc)
return rc;
target = tgtbuf;
}
if (mnt_context_is_lazy(cxt))
flags |= MNT_DETACH;
if (mnt_context_is_force(cxt))
flags |= MNT_FORCE;
DBG(CXT, ul_debugobj(cxt, "umount(2) [target='%s', flags=0x%08x]%s",
target, flags,
mnt_context_is_fake(cxt) ? " (FAKE)" : ""));
if (mnt_context_is_fake(cxt))
rc = 0;
else {
rc = flags ? umount2(target, flags) : umount(target);
if (rc < 0)
cxt->syscall_status = -errno;
free(tgtbuf);
}
/*
* try remount read-only
*/
if (rc < 0
&& cxt->syscall_status == -EBUSY
&& mnt_context_is_rdonly_umount(cxt)
&& src) {
mnt_context_set_mflags(cxt, (cxt->mountflags |
MS_REMOUNT | MS_RDONLY));
mnt_context_enable_loopdel(cxt, FALSE);
DBG(CXT, ul_debugobj(cxt,
"umount(2) failed [errno=%d] -- trying to remount read-only",
-cxt->syscall_status));
rc = mount(src, mnt_fs_get_target(cxt->fs), NULL,
MS_REMOUNT | MS_RDONLY, NULL);
if (rc < 0) {
cxt->syscall_status = -errno;
DBG(CXT, ul_debugobj(cxt,
"read-only re-mount(2) failed [errno=%d]",
-cxt->syscall_status));
return -cxt->syscall_status;
}
cxt->syscall_status = 0;
DBG(CXT, ul_debugobj(cxt, "read-only re-mount(2) success"));
return 0;
}
if (rc < 0) {
DBG(CXT, ul_debugobj(cxt, "umount(2) failed [errno=%d]",
-cxt->syscall_status));
return -cxt->syscall_status;
}
cxt->syscall_status = 0;
DBG(CXT, ul_debugobj(cxt, "umount(2) success"));
return 0;
}
/**
* mnt_context_prepare_umount:
* @cxt: mount context
*
* Prepare context for umounting, unnecessary for mnt_context_umount().
*
* Returns: 0 on success, and negative number in case of error.
*/
int mnt_context_prepare_umount(struct libmnt_context *cxt)
{
int rc;
struct libmnt_ns *ns_old;
if (!cxt || !cxt->fs || mnt_fs_is_swaparea(cxt->fs))
return -EINVAL;
if (!mnt_context_get_source(cxt) && !mnt_context_get_target(cxt))
return -EINVAL;
if (cxt->flags & MNT_FL_PREPARED)
return 0;
assert(cxt->helper_exec_status == 1);
assert(cxt->syscall_status == 1);
free(cxt->helper); /* be paranoid */
cxt->helper = NULL;
cxt->action = MNT_ACT_UMOUNT;
ns_old = mnt_context_switch_target_ns(cxt);
if (!ns_old)
return -MNT_ERR_NAMESPACE;
rc = lookup_umount_fs(cxt);
if (!rc)
rc = mnt_context_merge_mflags(cxt);
if (!rc)
rc = evaluate_permissions(cxt);
if (!rc && !cxt->helper) {
if (cxt->user_mountflags & MNT_MS_HELPER)
/* on helper= mount option based helper */
rc = prepare_helper_from_options(cxt, "helper");
if (!rc && !cxt->helper)
/* on fstype based helper */
rc = mnt_context_prepare_helper(cxt, "umount", NULL);
}
if (!rc && (cxt->user_mountflags & MNT_MS_LOOP))
/* loop option explicitly specified in mtab, detach this loop */
mnt_context_enable_loopdel(cxt, TRUE);
if (!rc && mnt_context_is_loopdel(cxt) && cxt->fs) {
const char *src = mnt_fs_get_srcpath(cxt->fs);
if (src && (!is_loopdev(src) || loopdev_is_autoclear(src)))
mnt_context_enable_loopdel(cxt, FALSE);
}
if (rc) {
DBG(CXT, ul_debugobj(cxt, "umount: preparing failed"));
return rc;
}
cxt->flags |= MNT_FL_PREPARED;
if (!mnt_context_switch_ns(cxt, ns_old))
return -MNT_ERR_NAMESPACE;
return rc;
}
/**
* mnt_context_do_umount:
* @cxt: mount context
*
* Umount filesystem by umount(2) or fork()+exec(/sbin/umount.type).
* Unnecessary for mnt_context_umount().
*
* See also mnt_context_disable_helpers().