/* returns: error = -1, success = 0 , unknown = 1 */
static int is_vers4(struct libmnt_context *cxt)
{
struct libmnt_fs *fs = mnt_context_get_fs(cxt);
struct libmnt_table *tb = NULL;
const char *src = mnt_context_get_source(cxt),
*tgt = mnt_context_get_target(cxt);
int rc = 1;
if (!src || !tgt)
return -1;
if (!mnt_fs_is_kernel(fs)) {
struct libmnt_table *tb = mnt_new_table_from_file("/proc/mounts");
if (!tb)
return -1;
fs = mnt_table_find_pair(tb, src, tgt, MNT_ITER_BACKWARD);
}
if (fs) {
const char *type = mnt_fs_get_fstype(fs);
if (type && strcmp(type, "nfs4") == 0)
rc = 0;
}
mnt_free_table(tb);
return rc;
}
/*
* 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, ok = 0;
struct libmnt_fs *fs;
assert(cxt);
assert(cxt->fs);
assert((cxt->flags & MNT_FL_MOUNTFLAGS_MERGED));
if (!cxt || !cxt->fs)
return -EINVAL;
if (!mnt_context_is_restricted(cxt))
return 0; /* superuser mount */
DBG(CXT, mnt_debug_h(cxt, "umount: evaluating permissions"));
if (!(cxt->flags & MNT_FL_TAB_APPLIED)) {
DBG(CXT, mnt_debug_h(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> */
}
/*
* 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 (mnt_fs_get_bindsrc(cxt->fs)) {
src = mnt_fs_get_bindsrc(cxt->fs);
DBG(CXT, mnt_debug_h(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 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 releation
* between loopdev and the file.
*/
fs = mnt_table_find_target(fstab, tgt, MNT_ITER_FORWARD);
if (fs) {
const char *dev = mnt_fs_get_srcpath(cxt->fs); /* devname from mtab */
if (!dev || !is_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_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, mnt_debug_h(cxt,
"umount: promiscuous setting ('users') 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 | MNT_MS_OWNER | MNT_MS_GROUP)) {
char *curr_user = NULL;
char *mtab_user = NULL;
size_t sz;
DBG(CXT, mnt_debug_h(cxt,
"umount: checking user=<username> from mtab"));
curr_user = mnt_get_username(getuid());
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_user_options(cxt->fs);
if (optstr && !mnt_optstr_get_option(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 is not allowed for you"));
return -EPERM;
}
