libfuse

mount.c
1 /*
2 FUSE: Filesystem in Userspace
3 Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
4
5 Architecture specific file system mounting (Linux).
6
7 This program can be distributed under the terms of the GNU LGPLv2.
8 See the file COPYING.LIB.
9 */
10
11 #include "config.h"
12 #include "fuse_i.h"
13 #include "fuse_misc.h"
14 #include "fuse_opt.h"
15 #include "mount_util.h"
16
17 #include <stdio.h>
18 #include <stdlib.h>
19 #include <unistd.h>
20 #include <stddef.h>
21 #include <string.h>
22 #include <fcntl.h>
23 #include <errno.h>
24 #include <poll.h>
25 #include <sys/socket.h>
26 #include <sys/un.h>
27 #include <sys/wait.h>
28 #include <sys/mount.h>
29
30 #ifdef __NetBSD__
31 #include <perfuse.h>
32
33 #define MS_RDONLY MNT_RDONLY
34 #define MS_NOSUID MNT_NOSUID
35 #define MS_NODEV MNT_NODEV
36 #define MS_NOEXEC MNT_NOEXEC
37 #define MS_SYNCHRONOUS MNT_SYNCHRONOUS
38 #define MS_NOATIME MNT_NOATIME
39
40 #define umount2(mnt, flags) unmount(mnt, (flags == 2) ? MNT_FORCE : 0)
41 #endif
42
43 #define FUSERMOUNT_PROG "fusermount3"
44 #define FUSE_COMMFD_ENV "_FUSE_COMMFD"
45
46 #ifndef HAVE_FORK
47 #define fork() vfork()
48 #endif
49
50 #ifndef MS_DIRSYNC
51 #define MS_DIRSYNC 128
52 #endif
53
54 enum {
55 KEY_KERN_FLAG,
56 KEY_KERN_OPT,
57 KEY_FUSERMOUNT_OPT,
58 KEY_SUBTYPE_OPT,
59 KEY_MTAB_OPT,
60 KEY_ALLOW_OTHER,
61 KEY_RO,
62 };
63
64 struct mount_opts {
65 int allow_other;
66 int flags;
67 int auto_unmount;
68 int blkdev;
69 char *fsname;
70 char *subtype;
71 char *subtype_opt;
72 char *mtab_opts;
73 char *fusermount_opts;
74 char *kernel_opts;
75 unsigned max_read;
76 };
77
78 #define FUSE_MOUNT_OPT(t, p) { t, offsetof(struct mount_opts, p), 1 }
79
80 static const struct fuse_opt fuse_mount_opts[] = {
81 FUSE_MOUNT_OPT("allow_other", allow_other),
82 FUSE_MOUNT_OPT("blkdev", blkdev),
83 FUSE_MOUNT_OPT("auto_unmount", auto_unmount),
84 FUSE_MOUNT_OPT("fsname=%s", fsname),
85 FUSE_MOUNT_OPT("max_read=%u", max_read),
86 FUSE_MOUNT_OPT("subtype=%s", subtype),
87 FUSE_OPT_KEY("allow_other", KEY_KERN_OPT),
88 FUSE_OPT_KEY("auto_unmount", KEY_FUSERMOUNT_OPT),
89 FUSE_OPT_KEY("blkdev", KEY_FUSERMOUNT_OPT),
90 FUSE_OPT_KEY("fsname=", KEY_FUSERMOUNT_OPT),
91 FUSE_OPT_KEY("subtype=", KEY_SUBTYPE_OPT),
92 FUSE_OPT_KEY("blksize=", KEY_KERN_OPT),
93 FUSE_OPT_KEY("default_permissions", KEY_KERN_OPT),
94 FUSE_OPT_KEY("context=", KEY_KERN_OPT),
95 FUSE_OPT_KEY("fscontext=", KEY_KERN_OPT),
96 FUSE_OPT_KEY("defcontext=", KEY_KERN_OPT),
97 FUSE_OPT_KEY("rootcontext=", KEY_KERN_OPT),
98 FUSE_OPT_KEY("max_read=", KEY_KERN_OPT),
99 FUSE_OPT_KEY("user=", KEY_MTAB_OPT),
100 FUSE_OPT_KEY("-r", KEY_RO),
101 FUSE_OPT_KEY("ro", KEY_KERN_FLAG),
102 FUSE_OPT_KEY("rw", KEY_KERN_FLAG),
103 FUSE_OPT_KEY("suid", KEY_KERN_FLAG),
104 FUSE_OPT_KEY("nosuid", KEY_KERN_FLAG),
105 FUSE_OPT_KEY("dev", KEY_KERN_FLAG),
106 FUSE_OPT_KEY("nodev", KEY_KERN_FLAG),
107 FUSE_OPT_KEY("exec", KEY_KERN_FLAG),
108 FUSE_OPT_KEY("noexec", KEY_KERN_FLAG),
109 FUSE_OPT_KEY("async", KEY_KERN_FLAG),
110 FUSE_OPT_KEY("sync", KEY_KERN_FLAG),
111 FUSE_OPT_KEY("dirsync", KEY_KERN_FLAG),
112 FUSE_OPT_KEY("atime", KEY_KERN_FLAG),
113 FUSE_OPT_KEY("noatime", KEY_KERN_FLAG),
114 FUSE_OPT_END
115 };
116
117 static void exec_fusermount(const char *argv[])
118 {
119 execv(FUSERMOUNT_DIR "/" FUSERMOUNT_PROG, (char **) argv);
120 execvp(FUSERMOUNT_PROG, (char **) argv);
121 }
122
123 void fuse_mount_version(void)
124 {
125 int pid = fork();
126 if (!pid) {
127 const char *argv[] = { FUSERMOUNT_PROG, "--version", NULL };
128 exec_fusermount(argv);
129 _exit(1);
130 } else if (pid != -1)
131 waitpid(pid, NULL, 0);
132 }
133
134 struct mount_flags {
135 const char *opt;
136 unsigned long flag;
137 int on;
138 };
139
140 static const struct mount_flags mount_flags[] = {
141 {"rw", MS_RDONLY, 0},
142 {"ro", MS_RDONLY, 1},
143 {"suid", MS_NOSUID, 0},
144 {"nosuid", MS_NOSUID, 1},
145 {"dev", MS_NODEV, 0},
146 {"nodev", MS_NODEV, 1},
147 {"exec", MS_NOEXEC, 0},
148 {"noexec", MS_NOEXEC, 1},
149 {"async", MS_SYNCHRONOUS, 0},
150 {"sync", MS_SYNCHRONOUS, 1},
151 {"atime", MS_NOATIME, 0},
152 {"noatime", MS_NOATIME, 1},
153 #ifndef __NetBSD__
154 {"dirsync", MS_DIRSYNC, 1},
155 #endif
156 {NULL, 0, 0}
157 };
158
159 unsigned get_max_read(struct mount_opts *o)
160 {
161 return o->max_read;
162 }
163
164 static void set_mount_flag(const char *s, int *flags)
165 {
166 int i;
167
168 for (i = 0; mount_flags[i].opt != NULL; i++) {
169 const char *opt = mount_flags[i].opt;
170 if (strcmp(opt, s) == 0) {
171 if (mount_flags[i].on)
172 *flags |= mount_flags[i].flag;
173 else
174 *flags &= ~mount_flags[i].flag;
175 return;
176 }
177 }
178 fuse_log(FUSE_LOG_ERR, "fuse: internal error, can't find mount flag\n");
179 abort();
180 }
181
182 static int fuse_mount_opt_proc(void *data, const char *arg, int key,
183 struct fuse_args *outargs)
184 {
185 (void) outargs;
186 struct mount_opts *mo = data;
187
188 switch (key) {
189 case KEY_RO:
190 arg = "ro";
191 /* fall through */
192 case KEY_KERN_FLAG:
193 set_mount_flag(arg, &mo->flags);
194 return 0;
195
196 case KEY_KERN_OPT:
197 return fuse_opt_add_opt(&mo->kernel_opts, arg);
198
199 case KEY_FUSERMOUNT_OPT:
200 return fuse_opt_add_opt_escaped(&mo->fusermount_opts, arg);
201
202 case KEY_SUBTYPE_OPT:
203 return fuse_opt_add_opt(&mo->subtype_opt, arg);
204
205 case KEY_MTAB_OPT:
206 return fuse_opt_add_opt(&mo->mtab_opts, arg);
207 }
208
209 /* Pass through unknown options */
210 return 1;
211 }
212
213 /* return value:
214 * >= 0 => fd
215 * -1 => error
216 */
217 static int receive_fd(int fd)
218 {
219 struct msghdr msg;
220 struct iovec iov;
221 char buf[1];
222 int rv;
223 size_t ccmsg[CMSG_SPACE(sizeof(int)) / sizeof(size_t)];
224 struct cmsghdr *cmsg;
225
226 iov.iov_base = buf;
227 iov.iov_len = 1;
228
229 memset(&msg, 0, sizeof(msg));
230 msg.msg_name = 0;
231 msg.msg_namelen = 0;
232 msg.msg_iov = &iov;
233 msg.msg_iovlen = 1;
234 /* old BSD implementations should use msg_accrights instead of
235 * msg_control; the interface is different. */
236 msg.msg_control = ccmsg;
237 msg.msg_controllen = sizeof(ccmsg);
238
239 while(((rv = recvmsg(fd, &msg, 0)) == -1) && errno == EINTR);
240 if (rv == -1) {
241 perror("recvmsg");
242 return -1;
243 }
244 if(!rv) {
245 /* EOF */
246 return -1;
247 }
248
249 cmsg = CMSG_FIRSTHDR(&msg);
250 if (cmsg->cmsg_type != SCM_RIGHTS) {
251 fuse_log(FUSE_LOG_ERR, "got control message of unknown type %d\n",
252 cmsg->cmsg_type);
253 return -1;
254 }
255 return *(int*)CMSG_DATA(cmsg);
256 }
257
258 void fuse_kern_unmount(const char *mountpoint, int fd)
259 {
260 int res;
261 int pid;
262
263 if (fd != -1) {
264 struct pollfd pfd;
265
266 pfd.fd = fd;
267 pfd.events = 0;
268 res = poll(&pfd, 1, 0);
269
270 /* Need to close file descriptor, otherwise synchronous umount
271 would recurse into filesystem, and deadlock.
272
273 Caller expects fuse_kern_unmount to close the fd, so close it
274 anyway. */
275 close(fd);
276
277 /* If file poll returns POLLERR on the device file descriptor,
278 then the filesystem is already unmounted or the connection
279 was severed via /sys/fs/fuse/connections/NNN/abort */
280 if (res == 1 && (pfd.revents & POLLERR))
281 return;
282 }
283
284 if (geteuid() == 0) {
285 fuse_mnt_umount("fuse", mountpoint, mountpoint, 1);
286 return;
287 }
288
289 res = umount2(mountpoint, 2);
290 if (res == 0)
291 return;
292
293 pid = fork();
294 if(pid == -1)
295 return;
296
297 if(pid == 0) {
298 const char *argv[] = { FUSERMOUNT_PROG, "-u", "-q", "-z",
299 "--", mountpoint, NULL };
300
301 exec_fusermount(argv);
302 _exit(1);
303 }
304 waitpid(pid, NULL, 0);
305 }
306
307 static int fuse_mount_fusermount(const char *mountpoint, struct mount_opts *mo,
308 const char *opts, int quiet)
309 {
310 int fds[2], pid;
311 int res;
312 int rv;
313
314 if (!mountpoint) {
315 fuse_log(FUSE_LOG_ERR, "fuse: missing mountpoint parameter\n");
316 return -1;
317 }
318
319 res = socketpair(PF_UNIX, SOCK_STREAM, 0, fds);
320 if(res == -1) {
321 perror("fuse: socketpair() failed");
322 return -1;
323 }
324
325 pid = fork();
326 if(pid == -1) {
327 perror("fuse: fork() failed");
328 close(fds[0]);
329 close(fds[1]);
330 return -1;
331 }
332
333 if(pid == 0) {
334 char env[10];
335 const char *argv[32];
336 int a = 0;
337
338 if (quiet) {
339 int fd = open("/dev/null", O_RDONLY);
340 if (fd != -1) {
341 dup2(fd, 1);
342 dup2(fd, 2);
343 }
344 }
345
346 argv[a++] = FUSERMOUNT_PROG;
347 if (opts) {
348 argv[a++] = "-o";
349 argv[a++] = opts;
350 }
351 argv[a++] = "--";
352 argv[a++] = mountpoint;
353 argv[a++] = NULL;
354
355 close(fds[1]);
356 fcntl(fds[0], F_SETFD, 0);
357 snprintf(env, sizeof(env), "%i", fds[0]);
358 setenv(FUSE_COMMFD_ENV, env, 1);
359 exec_fusermount(argv);
360 perror("fuse: failed to exec fusermount3");
361 _exit(1);
362 }
363
364 close(fds[0]);
365 rv = receive_fd(fds[1]);
366
367 if (!mo->auto_unmount) {
368 /* with auto_unmount option fusermount3 will not exit until
369 this socket is closed */
370 close(fds[1]);
371 waitpid(pid, NULL, 0); /* bury zombie */
372 }
373
374 if (rv >= 0)
375 fcntl(rv, F_SETFD, FD_CLOEXEC);
376
377 return rv;
378 }
379
380 #ifndef O_CLOEXEC
381 #define O_CLOEXEC 0
382 #endif
383
384 static int fuse_mount_sys(const char *mnt, struct mount_opts *mo,
385 const char *mnt_opts)
386 {
387 char tmp[128];
388 const char *devname = "/dev/fuse";
389 char *source = NULL;
390 char *type = NULL;
391 struct stat stbuf;
392 int fd;
393 int res;
394
395 if (!mnt) {
396 fuse_log(FUSE_LOG_ERR, "fuse: missing mountpoint parameter\n");
397 return -1;
398 }
399
400 res = stat(mnt, &stbuf);
401 if (res == -1) {
402 fuse_log(FUSE_LOG_ERR, "fuse: failed to access mountpoint %s: %s\n",
403 mnt, strerror(errno));
404 return -1;
405 }
406
407 if (mo->auto_unmount) {
408 /* Tell the caller to fallback to fusermount3 because
409 auto-unmount does not work otherwise. */
410 return -2;
411 }
412
413 fd = open(devname, O_RDWR | O_CLOEXEC);
414 if (fd == -1) {
415 if (errno == ENODEV || errno == ENOENT)
416 fuse_log(FUSE_LOG_ERR, "fuse: device not found, try 'modprobe fuse' first\n");
417 else
418 fuse_log(FUSE_LOG_ERR, "fuse: failed to open %s: %s\n",
419 devname, strerror(errno));
420 return -1;
421 }
422 if (!O_CLOEXEC)
423 fcntl(fd, F_SETFD, FD_CLOEXEC);
424
425 snprintf(tmp, sizeof(tmp), "fd=%i,rootmode=%o,user_id=%u,group_id=%u",
426 fd, stbuf.st_mode & S_IFMT, getuid(), getgid());
427
428 res = fuse_opt_add_opt(&mo->kernel_opts, tmp);
429 if (res == -1)
430 goto out_close;
431
432 source = malloc((mo->fsname ? strlen(mo->fsname) : 0) +
433 (mo->subtype ? strlen(mo->subtype) : 0) +
434 strlen(devname) + 32);
435
436 type = malloc((mo->subtype ? strlen(mo->subtype) : 0) + 32);
437 if (!type || !source) {
438 fuse_log(FUSE_LOG_ERR, "fuse: failed to allocate memory\n");
439 goto out_close;
440 }
441
442 strcpy(type, mo->blkdev ? "fuseblk" : "fuse");
443 if (mo->subtype) {
444 strcat(type, ".");
445 strcat(type, mo->subtype);
446 }
447 strcpy(source,
448 mo->fsname ? mo->fsname : (mo->subtype ? mo->subtype : devname));
449
450 res = mount(source, mnt, type, mo->flags, mo->kernel_opts);
451 if (res == -1 && errno == ENODEV && mo->subtype) {
452 /* Probably missing subtype support */
453 strcpy(type, mo->blkdev ? "fuseblk" : "fuse");
454 if (mo->fsname) {
455 if (!mo->blkdev)
456 sprintf(source, "%s#%s", mo->subtype,
457 mo->fsname);
458 } else {
459 strcpy(source, type);
460 }
461 res = mount(source, mnt, type, mo->flags, mo->kernel_opts);
462 }
463 if (res == -1) {
464 /*
465 * Maybe kernel doesn't support unprivileged mounts, in this
466 * case try falling back to fusermount3
467 */
468 if (errno == EPERM) {
469 res = -2;
470 } else {
471 int errno_save = errno;
472 if (mo->blkdev && errno == ENODEV &&
473 !fuse_mnt_check_fuseblk())
474 fuse_log(FUSE_LOG_ERR,
475 "fuse: 'fuseblk' support missing\n");
476 else
477 fuse_log(FUSE_LOG_ERR, "fuse: mount failed: %s\n",
478 strerror(errno_save));
479 }
480
481 goto out_close;
482 }
483
484 #ifndef IGNORE_MTAB
485 if (geteuid() == 0) {
486 char *newmnt = fuse_mnt_resolve_path("fuse", mnt);
487 res = -1;
488 if (!newmnt)
489 goto out_umount;
490
491 res = fuse_mnt_add_mount("fuse", source, newmnt, type,
492 mnt_opts);
493 free(newmnt);
494 if (res == -1)
495 goto out_umount;
496 }
497 #endif /* IGNORE_MTAB */
498 free(type);
499 free(source);
500
501 return fd;
502
503 out_umount:
504 umount2(mnt, 2); /* lazy umount */
505 out_close:
506 free(type);
507 free(source);
508 close(fd);
509 return res;
510 }
511
512 static int get_mnt_flag_opts(char **mnt_optsp, int flags)
513 {
514 int i;
515
516 if (!(flags & MS_RDONLY) && fuse_opt_add_opt(mnt_optsp, "rw") == -1)
517 return -1;
518
519 for (i = 0; mount_flags[i].opt != NULL; i++) {
520 if (mount_flags[i].on && (flags & mount_flags[i].flag) &&
521 fuse_opt_add_opt(mnt_optsp, mount_flags[i].opt) == -1)
522 return -1;
523 }
524 return 0;
525 }
526
527 struct mount_opts *parse_mount_opts(struct fuse_args *args)
528 {
529 struct mount_opts *mo;
530
531 mo = (struct mount_opts*) malloc(sizeof(struct mount_opts));
532 if (mo == NULL)
533 return NULL;
534
535 memset(mo, 0, sizeof(struct mount_opts));
536 mo->flags = MS_NOSUID | MS_NODEV;
537
538 if (args &&
539 fuse_opt_parse(args, mo, fuse_mount_opts, fuse_mount_opt_proc) == -1)
540 goto err_out;
541
542 return mo;
543
544 err_out:
545 destroy_mount_opts(mo);
546 return NULL;
547 }
548
549 void destroy_mount_opts(struct mount_opts *mo)
550 {
551 free(mo->fsname);
552 free(mo->subtype);
553 free(mo->fusermount_opts);
554 free(mo->subtype_opt);
555 free(mo->kernel_opts);
556 free(mo->mtab_opts);
557 free(mo);
558 }
559
560
561 int fuse_kern_mount(const char *mountpoint, struct mount_opts *mo)
562 {
563 int res = -1;
564 char *mnt_opts = NULL;
565
566 res = -1;
567 if (get_mnt_flag_opts(&mnt_opts, mo->flags) == -1)
568 goto out;
569 if (mo->kernel_opts && fuse_opt_add_opt(&mnt_opts, mo->kernel_opts) == -1)
570 goto out;
571 if (mo->mtab_opts && fuse_opt_add_opt(&mnt_opts, mo->mtab_opts) == -1)
572 goto out;
573
574 res = fuse_mount_sys(mountpoint, mo, mnt_opts);
575 if (res == -2) {
576 if (mo->fusermount_opts &&
577 fuse_opt_add_opt(&mnt_opts, mo->fusermount_opts) == -1)
578 goto out;
579
580 if (mo->subtype) {
581 char *tmp_opts = NULL;
582
583 res = -1;
584 if (fuse_opt_add_opt(&tmp_opts, mnt_opts) == -1 ||
585 fuse_opt_add_opt(&tmp_opts, mo->subtype_opt) == -1) {
586 free(tmp_opts);
587 goto out;
588 }
589
590 res = fuse_mount_fusermount(mountpoint, mo, tmp_opts, 1);
591 free(tmp_opts);
592 if (res == -1)
593 res = fuse_mount_fusermount(mountpoint, mo,
594 mnt_opts, 0);
595 } else {
596 res = fuse_mount_fusermount(mountpoint, mo, mnt_opts, 0);
597 }
598 }
599 out:
600 free(mnt_opts);
601 return res;
602 }
fuse_opt_add_opt_escaped
int fuse_opt_add_opt_escaped(char **opts, const char *opt)
Definition: fuse_opt.c:144
FUSE_OPT_END
#define FUSE_OPT_END
Definition: fuse_opt.h:104
fuse_log
void fuse_log(enum fuse_log_level level, const char *fmt,...)
Definition: fuse_log.c:33
fuse_opt_parse
int fuse_opt_parse(struct fuse_args *args, void *data, const struct fuse_opt opts[], fuse_opt_proc_t proc)
Definition: fuse_opt.c:398
fuse_opt
Definition: fuse_opt.h:77
fuse_args
Definition: fuse_opt.h:109
FUSE_OPT_KEY
#define FUSE_OPT_KEY(templ, key)
Definition: fuse_opt.h:98
fuse_opt_add_opt
int fuse_opt_add_opt(char **opts, const char *opt)
Definition: fuse_opt.c:139