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1 /* mount.c - mount filesystems
2  *
3  * Copyright 2014 Rob Landley <rob@landley.net>
4  *
5  * See http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/mount.html
6  *
7  * Note: -hV is bad spec, haven't implemented -FsLU yet
8  * no mtab (/proc/mounts does it) so -n is NOP.
9  * TODO mount -o loop,autoclear (linux git 96c5865559ce)
10 
11 USE_MOUNT(NEWTOY(mount, "?O:afnrvwt:o*[-rw]", TOYFLAG_BIN|TOYFLAG_STAYROOT))
12 //USE_NFSMOUNT(NEWTOY(nfsmount, "?<2>2", TOYFLAG_USR|TOYFLAG_BIN|TOYFLAG_STAYROOT))
13 
14 config MOUNT
15   bool "mount"
16   default y
17   help
18     usage: mount [-f] [-t TYPE] [-o OPTION,] [[DEVICE] DIR]
19 
20     Mount new filesystem(s) on directories. With no arguments, display existing
21     mounts.
22 
23     -f	Fake it (don't actually mount)
24     -t	Specify filesystem type
25     -o	Mount options
26 
27     OPTIONS is a comma separated list of options, which can also be supplied
28     as --longopts.
29 
30     Autodetects loopback mounts (a file on a directory) and bind mounts (file
31     on file, directory on directory), so you don't need to say --bind or --loop.
32     You can also "mount -a /path" to mount everything in /etc/fstab under /path,
33     even if it's noauto. DEVICE starting with UUID= is identified by blkid -U.
34 
35 #config SMBMOUNT
36 #  bool "smbmount"
37 #  deault n
38 #  helo
39 #    usage: smbmount SHARE DIR
40 #
41 #    Mount smb share with user/pasword prompt as necessary.
42 #
43 #config NFSMOUNT
44 #  bool "nfsmount"
45 #  default n
46 #  help
47 #    usage: nfsmount SHARE DIR
48 #
49 #    Invoke an eldrich horror from the dawn of time.
50 */
51 
52 #define FOR_mount
53 #include "toys.h"
54 
GLOBALS(struct arg_list * optlist;char * type;char * bigO;unsigned long flags;char * opts;int okuser;)55 GLOBALS(
56   struct arg_list *optlist;
57   char *type;
58   char *bigO;
59 
60   unsigned long flags;
61   char *opts;
62   int okuser;
63 )
64 
65 // mount.tests should check for all of this:
66 // TODO detect existing identical mount (procfs with different dev name?)
67 // TODO user, users, owner, group, nofail
68 // TODO -p (passfd)
69 // TODO -a -t notype,type2
70 // TODO --subtree
71 // TODO --rbind, -R
72 // TODO make "mount --bind,ro old new" work (implicit -o remount)
73 // TODO mount -a
74 // TODO mount -o remount
75 // TODO fstab: lookup default options for mount
76 // TODO implement -v
77 // TODO "mount -a -o remount,ro" should detect overmounts
78 // TODO work out how that differs from "mount -ar"
79 // TODO what if you --bind mount a block device somewhere (file, dir, dev)
80 // TODO "touch servername; mount -t cifs servername path"
81 // TODO mount -o remount a user mount
82 // TODO mount image.img sub (auto-loopback) then umount image.img
83 // TODO mount UUID=blah
84 
85 // Strip flags out of comma separated list of options, return flags,.
86 static long flag_opts(char *new, long flags, char **more)
87 {
88   struct {
89     char *name;
90     long flags;
91   } opts[] = {
92     // NOPs (we autodetect --loop and --bind)
93     {"loop", 0}, {"bind", 0}, {"defaults", 0}, {"quiet", 0},
94     {"user", 0}, {"nouser", 0}, // checked in fstab, ignored in -o
95     {"ro", MS_RDONLY}, {"rw", ~MS_RDONLY},
96     {"nosuid", MS_NOSUID}, {"suid", ~MS_NOSUID},
97     {"nodev", MS_NODEV}, {"dev", ~MS_NODEV},
98     {"noexec", MS_NOEXEC}, {"exec", ~MS_NOEXEC},
99     {"sync", MS_SYNCHRONOUS}, {"async", ~MS_SYNCHRONOUS},
100     {"noatime", MS_NOATIME}, {"atime", ~MS_NOATIME},
101     {"norelatime", ~MS_RELATIME}, {"relatime", MS_RELATIME},
102     {"nodiratime", MS_NODIRATIME}, {"diratime", ~MS_NODIRATIME},
103     {"loud", ~MS_SILENT},
104     {"shared", MS_SHARED}, {"rshared", MS_SHARED|MS_REC},
105     {"slave", MS_SLAVE}, {"rslave", MS_SLAVE|MS_REC},
106     {"private", MS_PRIVATE}, {"rprivate", MS_SLAVE|MS_REC},
107     {"unbindable", MS_UNBINDABLE}, {"runbindable", MS_UNBINDABLE|MS_REC},
108     {"remount", MS_REMOUNT}, {"move", MS_MOVE},
109     // mand dirsync rec iversion strictatime
110   };
111 
112   if (new) for (;;) {
113     char *comma = strchr(new, ',');
114     int i;
115 
116     if (comma) *comma = 0;
117 
118     // If we recognize an option, apply flags
119     for (i = 0; i < ARRAY_LEN(opts); i++) if (!strcasecmp(opts[i].name, new)) {
120       long ll = opts[i].flags;
121 
122       if (ll < 0) flags &= ll;
123       else flags |= ll;
124 
125       break;
126     }
127 
128     // If we didn't recognize it, keep string version
129     if (more && i == ARRAY_LEN(opts)) {
130       i = *more ? strlen(*more) : 0;
131       *more = xrealloc(*more, i + strlen(new) + 2);
132       if (i) (*more)[i++] = ',';
133       strcpy(i+*more, new);
134     }
135 
136     if (!comma) break;
137     *comma = ',';
138     new = comma + 1;
139   }
140 
141   return flags;
142 }
143 
144 // Shell out to a program, returning the output string or NULL on error
tortoise(int loud,char ** cmd)145 static char *tortoise(int loud, char **cmd)
146 {
147   int rc, pipe, len;
148   pid_t pid;
149 
150   pid = xpopen(cmd, &pipe, 1);
151   len = readall(pipe, toybuf, sizeof(toybuf)-1);
152   rc = xpclose(pid, pipe);
153   if (!rc && len > 1) {
154     if (toybuf[len-1] == '\n') --len;
155     toybuf[len] = 0;
156     return toybuf;
157   }
158   if (loud) error_msg("%s failed %d", *cmd, rc);
159 
160   return 0;
161 }
162 
mount_filesystem(char * dev,char * dir,char * type,unsigned long flags,char * opts)163 static void mount_filesystem(char *dev, char *dir, char *type,
164   unsigned long flags, char *opts)
165 {
166   FILE *fp = 0;
167   int rc = EINVAL;
168   char *buf = 0;
169 
170   if (FLAG(f)) return;
171 
172   if (strstart(&dev, "UUID=")) {
173     char *s = tortoise(0, (char *[]){"blkid", "-U", dev, 0});
174 
175     if (!dev) return error_msg("No uuid %s", dev);
176     dev = s;
177   }
178 
179   // Autodetect bind mount or filesystem type
180 
181   if (type && !strcmp(type, "auto")) type = 0;
182   if (flags & MS_MOVE) {
183     if (type) error_exit("--move with -t");
184   } else if (!type) {
185     struct stat stdev, stdir;
186 
187     // file on file or dir on dir is a --bind mount.
188     if (!stat(dev, &stdev) && !stat(dir, &stdir)
189         && ((S_ISREG(stdev.st_mode) && S_ISREG(stdir.st_mode))
190             || (S_ISDIR(stdev.st_mode) && S_ISDIR(stdir.st_mode))))
191     {
192       flags |= MS_BIND;
193     } else fp = xfopen("/proc/filesystems", "r");
194   } else if (!strcmp(type, "ignore")) return;
195   else if (!strcmp(type, "swap"))
196     toys.exitval |= xrun((char *[]){"swapon", "--", dev, 0});
197 
198   for (;;) {
199     int fd = -1, ro = 0;
200 
201     // If type wasn't specified, try all of them in order.
202     if (fp && !buf) {
203       size_t i;
204 
205       if (getline(&buf, &i, fp)<0) {
206         error_msg("%s: need -t", dev);
207         break;
208       }
209       type = buf;
210       // skip nodev devices
211       if (!isspace(*type)) {
212         free(buf);
213         buf = 0;
214 
215         continue;
216       }
217       // trim whitespace
218       while (isspace(*type)) type++;
219       i = strlen(type);
220       if (i) type[i-1] = 0;
221     }
222     if (FLAG(v))
223       printf("try '%s' type '%s' on '%s'\n", dev, type, dir);
224     for (;;) {
225       rc = mount(dev, dir, type, flags, opts);
226       // Did we succeed, fail unrecoverably, or already try read-only?
227       if (!rc || (errno != EACCES && errno != EROFS) || (flags&MS_RDONLY))
228         break;
229       // If we haven't already tried it, use the BLKROSET ioctl to ensure
230       // that the underlying device isn't read-only.
231       if (fd == -1) {
232         if (FLAG(v))
233           printf("trying BLKROSET ioctl on '%s'\n", dev);
234         if (-1 != (fd = open(dev, O_RDONLY))) {
235           rc = ioctl(fd, BLKROSET, &ro);
236           close(fd);
237           if (!rc) continue;
238         }
239       }
240       fprintf(stderr, "'%s' is read-only\n", dev);
241       flags |= MS_RDONLY;
242     }
243 
244     // Trying to autodetect loop mounts like bind mounts above (file on dir)
245     // isn't good enough because "mount -t ext2 fs.img dir" is valid, but if
246     // you _do_ accept loop mounts with -t how do you tell "-t cifs" isn't
247     // looking for a block device if it's not in /proc/filesystems yet
248     // because the fs module won't be loaded until you try the mount, and
249     // if you can't then DEVICE existing as a file would cause a false
250     // positive loopback mount (so "touch servername" becomes a potential
251     // denial of service attack...)
252     //
253     // Solution: try the mount, let the kernel tell us it wanted a block
254     // device, then do the loopback setup and retry the mount.
255 
256     if (rc && errno == ENOTBLK) {
257       dev = tortoise(1, (char *[]){"losetup",
258         (flags&MS_RDONLY) ? "-fsr" : "-fs", dev, 0});
259       if (!dev) break;
260     }
261 
262     free(buf);
263     buf = 0;
264     if (!rc) break;
265     if (fp && (errno == EINVAL || errno == EBUSY)) continue;
266 
267     perror_msg("'%s'->'%s'", dev, dir);
268 
269     break;
270   }
271   if (fp) fclose(fp);
272 }
273 
mount_main(void)274 void mount_main(void)
275 {
276   char *opts = 0, *dev = 0, *dir = 0, **ss;
277   long flags = MS_SILENT;
278   struct arg_list *o;
279   struct mtab_list *mtl, *mtl2 = 0, *mm, *remount;
280 
281 // TODO
282 // remount
283 //   - overmounts
284 // shared subtree
285 // -o parsed after fstab options
286 // test if mountpoint already exists (-o noremount?)
287 
288   // First pass; just accumulate string, don't parse flags yet. (This is so
289   // we can modify fstab entries with -a, or mtab with remount.)
290 
291   for (o = TT.optlist; o; o = o->next) comma_collate(&opts, o->arg);
292   if (FLAG(r)) comma_collate(&opts, "ro");
293   if (FLAG(w)) comma_collate(&opts, "rw");
294 
295   // Treat each --option as -o option
296   for (ss = toys.optargs; *ss; ss++) {
297     char *sss = *ss;
298 
299     // If you realy, really want to mount a file named "--", we support it.
300     if (sss[0]=='-' && sss[1]=='-' && sss[2]) comma_collate(&opts, sss+2);
301     else if (!dev) dev = sss;
302     else if (!dir) dir = sss;
303     // same message as lib/args.c ">2" which we can't use because --opts count
304     else error_exit("Max 2 arguments\n");
305   }
306 
307   if (FLAG(a) && dir) error_exit("-a with >1 arg");
308 
309   // For remount we need _last_ match (in case of overmounts), so traverse
310   // in reverse order. (Yes I'm using remount as a boolean for a bit here,
311   // the double cast is to get gcc to shut up about it.)
312   remount = (void *)(long)comma_scan(opts, "remount", 0);
313   if ((FLAG(a) && !access("/proc/mounts", R_OK)) || remount) {
314     mm = dlist_terminate(mtl = mtl2 = xgetmountlist(0));
315     if (remount) remount = mm;
316   }
317 
318   // Do we need to do an /etc/fstab trawl?
319   // This covers -a, -o remount, one argument, all user mounts
320   if (!dev && !toys.argv[1]) {
321     for (mtl = xgetmountlist(0); mtl && (mm = dlist_pop(&mtl)); free(mm)) {
322       char *s = 0;
323 
324       if (TT.type && strcmp(TT.type, mm->type)) continue;
325       if (*mm->device == '/') s = xabspath(mm->device, 0);
326       xprintf("%s on %s type %s\n",
327               s ? s : mm->device, mm->dir, mm->type);
328       free(s);
329     }
330 
331   // two arguments
332   } else {
333     char *more = 0;
334 
335     flags = flag_opts(opts, flags, &more);
336     if (dir) mount_filesystem(dev, dir, TT.type, flags, more);
337     if (CFG_TOYBOX_FREE) free(more);
338   }
339 }
340