/*
* Copyright (C) 2010 Karel Zak <kzak@redhat.com>
*
* This file may be redistributed under the terms of the
* GNU Lesser General Public License.
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/wait.h>
#include <sys/mount.h>
#include "c.h"
#include "pathnames.h"
#include "strutils.h"
#include "mountP.h"
static int lookup_umount_fs(mnt_context *cxt)
{
int rc;
const char *tgt;
mnt_tab *mtab;
mnt_fs *fs;
tgt = mnt_fs_get_target(cxt->fs);
if (!tgt) {
DBG(CXT, mnt_debug_h(cxt, "umount: undefined target"));
return -EINVAL;
}
rc = mnt_context_get_mtab(cxt, &mtab);
if (rc) {
DBG(CXT, mnt_debug_h(cxt, "umount: failed to read mtab"));
return rc;
}
fs = mnt_tab_find_target(mtab, tgt, MNT_ITER_BACKWARD);
if (!fs) {
/* maybe the option is source rather than target (mountpoint) */
fs = mnt_tab_find_source(mtab, tgt, MNT_ITER_BACKWARD);
if (fs) {
mnt_fs *fs1 = mnt_tab_find_target(mtab,
mnt_fs_get_target(fs),
MNT_ITER_BACKWARD);
if (!fs1) {
DBG(CXT, mnt_debug_h(cxt, "mtab is broken?!?!"));
return -EINVAL;
}
if (fs != fs1) {
/* Something was stacked over `file' on the
* same mount point. */
DBG(CXT, mnt_debug_h(cxt,
"umount: %s: %s is mounted "
"over it on the same point",
tgt, mnt_fs_get_source(fs1)));
return -EINVAL;
}
}
}
if (!fs) {
DBG(CXT, mnt_debug_h(cxt, "cannot found %s in mtab", tgt));
return 0;
}
/* copy from mtab/fstab to our FS description
*/
rc = mnt_fs_set_source(cxt->fs, mnt_fs_get_source(fs));
if (!rc)
rc = mnt_fs_set_target(cxt->fs, mnt_fs_get_target(fs));
if (!rc && !mnt_fs_get_fstype(cxt->fs))
rc = mnt_fs_set_fstype(cxt->fs, mnt_fs_get_fstype(fs));
if (!rc)
rc = mnt_fs_set_optstr(cxt->fs, mnt_fs_get_optstr(fs));
cxt->flags |= MNT_FL_TAB_APPLIED;
return rc;
}
/* check if @devname is loopdev and if the device is associated
* with a source from @fstab_fs
*
* TODO : move this to loopdev.c
*/
static int mnt_loopdev_associated_fs(const char *devname, mnt_fs *fs)
{
uintmax_t offset = 0;
const char *src;
char *val, *optstr;
size_t valsz;
/* check if it begins with /dev/loop */
if (strncmp(devname, _PATH_DEV_LOOP, sizeof(_PATH_DEV_LOOP)))
return 0;
src = mnt_fs_get_srcpath(fs);
if (!src)
return 0;
/* check for offset option in @fs */
optstr = (char *) mnt_fs_get_optstr(fs);
if (optstr && !mnt_optstr_get_option(optstr, "offset=", &val, &valsz)) {
int rc;
val = strndup(val, valsz);
if (!val)
return 0;
rc = strtosize(val, &offset);
free(val);
if (rc)
return 0;
}
/* TODO:
* if (mnt_loopdev_associated_file(devname, src, offset))
* return 1;
*/
return 0;
}
/*
* Note that cxt->fs contains relevant mtab entry!
*/
static int evaluate_permissions(mnt_context *cxt)
{
mnt_tab *fstab;
unsigned long u_flags;
const char *tgt, *src, *optstr;
int rc, ok = 0;
mnt_fs *fs;
if (!cxt || !cxt->fs)
return -EINVAL;
if (!mnt_context_is_restricted(cxt))
return 0; /* superuser mount */
if (!(cxt->flags & MNT_FL_TAB_APPLIED)) {
DBG(CXT, mnt_debug_h(cxt,
"cannot found %s in mtab and you are not root",
mnt_fs_get_target(cxt->fs)));
goto eperm;
}
mnt_context_get_userspace_mountflags(cxt, &u_flags);
if (!(cxt->flags & MNT_FL_NOHELPERS) && (u_flags & MNT_MS_UHELPER)) {
char *suffix = NULL;
char *o = (char *) mnt_fs_get_optstr(cxt->fs);
size_t valsz;
rc = mnt_optstr_get_option(o, "uhelper", &suffix, &valsz);
if (!rc) {
suffix = strndup(suffix, valsz);
if (!suffix)
return -ENOMEM;
rc = mnt_context_prepare_helper(cxt, "umount", suffix);
}
if (rc < 0)
return rc;
if (cxt->helper)
return 0; /* we'll call /sbin/umount.<uhelper> */
}
/*
* User mounts has 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 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 file, but for the pair (dev,file) in fstab.
*/
fs = mnt_tab_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 releation
* between loopdev and the file.
*/
fs = mnt_tab_find_target(fstab, tgt, MNT_ITER_FORWARD);
if (fs) {
const char *dev = mnt_fs_get_srcpath(cxt->fs); /* devname from mtab */
if (!dev || !mnt_loopdev_associated_fs(dev, fs))
fs = NULL;
}
if (!fs) {
DBG(CXT, mnt_debug_h(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_optstr(fs);
if (!optstr)
goto eperm;
if (mnt_optstr_get_userspace_mountflags(optstr, &u_flags))
goto eperm;
if (u_flags & MNT_MS_USERS)
/* promiscuous setting in fstab */
return 0;
/*
* Check user=<username> setting from mtab if there is user, owner or
* group option in /etc/fstab
*/
if ((u_flags & MNT_MS_USER) || (u_flags & MNT_MS_OWNER) ||
(u_flags & MNT_MS_GROUP)) {
char *curr_user = mnt_get_username(getuid());
char *mtab_user = NULL;
size_t sz;
if (!curr_user) {
DBG(CXT, mnt_debug_h(cxt, "umount %s: cannot "
"convert %d to username",
tgt, getuid()));
goto eperm;
}
/* get options from mtab */
optstr = mnt_fs_get_optstr(cxt->fs);
if (optstr && !mnt_optstr_get_option((char *) optstr,
"user", &mtab_user, &sz) && sz)
ok = !strncmp(curr_user, mtab_user, sz);
}
if (ok) {
DBG(CXT, mnt_debug_h(cxt, "umount %s is allowed", tgt));
return 0;
}
eperm:
DBG(CXT, mnt_debug_h(cxt, "umount %s is not allowed for you", tgt));
return -EPERM;
}
static int exec_helper(mnt_context *cxt)
{
int rc;
assert(cxt);
assert(cxt->fs);
assert(cxt->helper);
DBG_FLUSH;
switch (fork()) {
case 0:
{
const char *args[10], *type;
int i = 0;
if (setgid(getgid()) < 0)
exit(EXIT_FAILURE);
if (setuid(getuid()) < 0)
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 (cxt->flags & MNT_FL_NOMTAB)
args[i++] = "-n"; /* 3 */
if (cxt->flags & MNT_FL_LAZY)
args[i++] = "-l"; /* 4 */
if (cxt->flags & MNT_FL_FORCE)
args[i++] = "-f"; /* 5 */
if (cxt->flags & MNT_FL_VERBOSE)
args[i++] = "-v"; /* 6 */
if (cxt->flags & MNT_FL_RDONLY_UMOUNT)
args[i++] = "-r"; /* 7 */
if (type && !endswith(cxt->helper, type)) {
args[i++] = "-t"; /* 8 */
args[i++] = (char *) type; /* 9 */
}
args[i] = NULL; /* 10 */
#ifdef CONFIG_LIBMOUNT_DEBUG
i = 0;
for (i = 0; args[i]; i++)
DBG(CXT, mnt_debug_h(cxt, "argv[%d] = \"%s\"",
i, args[i]));
#endif
DBG_FLUSH;
execv(cxt->helper, (char * const *) args);
exit(EXIT_FAILURE);
}
default:
{
int st;
wait(&st);
cxt->helper_status = WIFEXITED(st) ? WEXITSTATUS(st) : -1;
DBG(CXT, mnt_debug_h(cxt, "%s executed [status=%d]",
cxt->helper, cxt->helper_status));
rc = 0;
break;
}
case -1:
rc = -errno;
DBG(CXT, mnt_debug_h(cxt, "fork() failed"));
break;
}
return rc;
}
static int do_umount(mnt_context *cxt)
{
int rc = 0;
const char *src, *target;
assert(cxt);
assert(cxt->fs);
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;
if (cxt->flags & MNT_FL_FAKE)
return 0;
if (cxt->flags & MNT_FL_LAZY)
rc = umount2(target, MNT_DETACH);
else if (cxt->flags & MNT_FL_FORCE) {
rc = umount2(target, MNT_FORCE);
if (rc < 0 && errno == ENOSYS)
rc = umount(target);
} else
rc = umount(target);
if (rc < 0)
cxt->syscall_errno = errno;
/*
* try remount read-only
*/
if (rc < 0 && cxt->syscall_errno == EBUSY &&
(cxt->flags & MNT_FL_RDONLY_UMOUNT) && src) {
cxt->mountflags |= MS_REMOUNT | MS_RDONLY;
cxt->flags &= ~MNT_FL_LOOPDEL;
DBG(CXT, mnt_debug_h(cxt, "umount(2) failed [errno=%d] -- "
"tring remount read-only",
cxt->syscall_errno));
rc = mount(src, target, NULL,
MS_MGC_VAL | MS_REMOUNT | MS_RDONLY, NULL);
if (rc < 0) {
cxt->syscall_errno = errno;
DBG(CXT, mnt_debug_h(cxt, "read-only re-mount(2) failed "
"[errno=%d]",
cxt->syscall_errno));
return -cxt->syscall_errno;
}
cxt->syscall_errno = 0;
DBG(CXT, mnt_debug_h(cxt, "read-only re-mount(2) success"));
return 0;
}
if (rc < 0) {
DBG(CXT, mnt_debug_h(cxt, "umount(2) failed [errno=%d]",
cxt->syscall_errno));
return -cxt->syscall_errno;
}
DBG(CXT, mnt_debug_h(cxt, "umount(2) success"));
return 0;
}
/**
* mnt_context_prepare_umount:
* @cxt: mount context
*
* This function:
* - read information from fstab/mtab (if necessary)
* - check premissions
* - prepare for mtab update (if necessary)
*
* It's strongly recommended to use this function before mnt_context_do_umount().
*
* Returns: 0 on success, and negative number in case of error.
*/
int mnt_context_prepare_umount(mnt_context *cxt)
{
int rc = 0;
if (!cxt)
return -EINVAL;
if (!cxt->fs || (!mnt_fs_get_source(cxt->fs) &&
!mnt_fs_get_target(cxt->fs)))
return -EINVAL;
free(cxt->helper); /* be paranoid */
cxt->helper = NULL;
rc = lookup_umount_fs(cxt);
if (!rc)
rc = evaluate_permissions(cxt);
if (!rc && !cxt->helper)
rc = mnt_context_prepare_helper(cxt, "umount", NULL);
/* TODO
if ((cxt->flags & MNT_FL_LOOPDEL) &&
(!mnt_is_loopdev(src) || mnt_loopdev_is_autoclear(src)))
cxt->flags &= ~MNT_FL_LOOPDEL;
*/
if (!rc)
rc = mnt_context_prepare_update(cxt, MNT_ACT_UMOUNT);
if (!rc) {
DBG(CXT, mnt_debug_h(cxt, "umount sucessfully prepared"));
return 0;
}
DBG(CXT, mnt_debug_h(cxt, "umount prepare failed"));
return rc;
}
/**
* mnt_context_do_umount:
* @cxt: mount context
*
* Umount filesystem by umount(2) or fork()+exec(/sbin/umount.<type>).
*
* See also mnt_context_disable_helpers().
*
* Returns: 0 on success, and negative number in case of error.
*/
int mnt_context_do_umount(mnt_context *cxt)
{
if (!cxt || !cxt->fs || (cxt->fs->flags & MNT_FS_SWAP))
return -EINVAL;
return do_umount(cxt);
}
/**
* mnt_context_post_umount:
* @cxt: mount context
*
* Updates mtab and detroy loopdev etc. This function should be always called after
* mnt_context_do_umount().
*
* Returns: 0 on success, and negative number in case of error.
*/
int mnt_context_post_umount(mnt_context *cxt)
{
int rc = 0;
if (!cxt)
return -EINVAL;
if (cxt->syscall_errno || cxt->helper)
return 0;
/* TODO
if (cxt->flags & MNT_FL_LOOPDEL)
rc = mnt_loopdev_clean(mnt_fs_get_source(cxt->fs));
*/
if (cxt->flags & MNT_FL_NOMTAB)
return rc;
if ((cxt->flags & MNT_FL_RDONLY_UMOUNT) &&
(cxt->mountflags & (MS_RDONLY | MS_REMOUNT))) {
/*
* refresh update to handle remount to read-only
*/
rc = mnt_context_prepare_update(cxt, MNT_ACT_MOUNT);
if (rc)
return rc;
}
/*
* Update /etc/mtab or /var/run/mount/mountinfo
*/
if (cxt->update && !mnt_update_is_pointless(cxt->update)) {
rc = mnt_update_file(cxt->update);
if (!rc)
return rc;
}
return rc;
}
/**
* mnt_context_umount_strerror
* @cxt: mount context
* @buf: buffer
* @bufsiz: size of the buffer
*
* Returns: 0 or negative number in case of error.
*/
int mnt_context_umount_strerror(mnt_context *cxt, char *buf, size_t bufsiz)
{
/* TODO: based on cxt->syscall_errno or cxt->helper_status */
return 0;
}
