1/* umount.c - Unmount a mount point.
2 *
3 * Copyright 2012 Rob Landley <rob@landley.net>
4 *
5 * See http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/umount.html
6 *
7 * Note: -n (/etc/mtab) is obsolete, /proc/mounts replaced it. Neither chroot
8 * nor per-process mount namespaces can work sanely with mtab. The kernel
9 * tracks mount points now, a userspace application can't do so anymore.
10
11USE_UMOUNT(NEWTOY(umount, "ndDflrat*v[!na]", TOYFLAG_BIN|TOYFLAG_STAYROOT))
12
13config UMOUNT
14  bool "umount"
15  default y
16  help
17    usage: umount [-a [-t TYPE[,TYPE...]]] [-vrfD] [DIR...]
18
19    Unmount the listed filesystems.
20
21    -a	Unmount all mounts in /proc/mounts instead of command line list
22    -D  Don't free loopback device(s).
23    -f  Force unmount.
24    -l  Lazy unmount (detach from filesystem now, close when last user does).
25    -n	Don't use /proc/mounts
26    -r  Remount read only if unmounting fails.
27    -t	Restrict "all" to mounts of TYPE (or use "noTYPE" to skip)
28    -v	Verbose
29*/
30
31#define FOR_umount
32#include "toys.h"
33
34GLOBALS(
35  struct arg_list *t;
36
37  char *types;
38)
39
40// todo (done?)
41//   borrow df code to identify filesystem?
42//   umount -a from fstab
43//   umount when getpid() not 0, according to fstab
44//   lookup mount: losetup -d, bind, file, block
45//   loopback delete
46//   fstab -o user
47
48// TODO
49// swapon, swapoff
50
51static void do_umount(char *dir, char *dev, int flags)
52{
53  // is it ok for this user to umount this mount?
54  if (CFG_TOYBOX_SUID && getuid()) {
55    struct mtab_list *mt = dlist_terminate(xgetmountlist("/etc/fstab"));
56    int len, user = 0;
57
58    while (mt) {
59      struct mtab_list *mtemp = mt;
60      char *s;
61
62      if (!strcmp(mt->dir, dir)) while ((s = comma_iterate(&mt->opts, &len))) {
63        if (len == 4 && strncmp(s, "user", 4)) user = 1;
64        else if (len == 6 && strncmp(s, "nouser", 6)) user = 0;
65      }
66
67      mt = mt->next;
68      free(mtemp);
69    }
70
71    if (!user) {
72      error_msg("not root");
73
74      return;
75    }
76  }
77
78  if (!umount2(dir, flags)) {
79    if (toys.optflags & FLAG_v) xprintf("%s unmounted\n", dir);
80
81    // Attempt to disassociate loopback device. This ioctl should be ignored
82    // for anything else, because lanana allocated ioctl range 'L' to loopback
83    if (dev && !(toys.optflags & FLAG_D)) {
84      int lfd = open(dev, O_RDONLY);
85
86      if (lfd != -1) {
87        // This is LOOP_CLR_FD, fetching it from headers is awkward
88        if (!ioctl(lfd, 0x4C01) && (toys.optflags & FLAG_v))
89          xprintf("%s cleared\n", dev);
90        close(lfd);
91      }
92    }
93
94    return;
95  }
96
97  if (toys.optflags & FLAG_r) {
98    if (!mount("", dir, "", MS_REMOUNT|MS_RDONLY, "")) {
99      if (toys.optflags & FLAG_v) xprintf("%s remounted ro\n", dir);
100      return;
101    }
102  }
103
104  perror_msg_raw(dir);
105}
106
107void umount_main(void)
108{
109  char **optargs, *pm = "/proc/mounts";
110  struct mtab_list *mlsave = 0, *mlrev = 0, *ml;
111  int flags=0;
112
113  if (!toys.optc && !(toys.optflags & FLAG_a))
114    error_exit("Need 1 arg or -a");
115
116  if (toys.optflags & FLAG_f) flags |= MNT_FORCE;
117  if (toys.optflags & FLAG_l) flags |= MNT_DETACH;
118
119  // Load /proc/mounts and get a reversed list (newest first)
120  // We use the list both for -a, and to umount /dev/name or do losetup -d
121  if (!(toys.optflags & FLAG_n) && !access(pm, R_OK))
122    mlrev = dlist_terminate(mlsave = xgetmountlist(pm));
123
124  // Unmount all: loop through mounted filesystems, skip -t, unmount the rest
125  if (toys.optflags & FLAG_a) {
126    char *typestr = 0;
127    struct arg_list *tal;
128
129    for (tal = TT.t; tal; tal = tal->next) comma_collate(&typestr, tal->arg);
130    for (ml = mlrev; ml; ml = ml->prev)
131      if (mountlist_istype(ml, typestr)) do_umount(ml->dir, ml->device, flags);
132    if (CFG_TOYBOX_FREE) {
133      free(typestr);
134      llist_traverse(mlsave, free);
135    }
136  // TODO: under what circumstances do we umount non-absolute path?
137  } else for (optargs = toys.optargs; *optargs; optargs++) {
138    char *abs = xabspath(*optargs, 0);
139
140    for (ml = abs ? mlrev : 0; ml; ml = ml->prev) {
141      if (!strcmp(ml->dir, abs)) break;
142      if (!strcmp(ml->device, abs)) {
143        free(abs);
144        abs = ml->dir;
145        break;
146      }
147    }
148
149    do_umount(abs ? abs : *optargs, ml ? ml->device : 0, flags);
150    if (ml && abs != ml->dir) free(abs);
151  }
152}
153