path: root/libfuse-lite/mount_util.c (plain)
blob: 75a7ee63cfd4b50dcb4fb97aaaa41dbd88335acc

1	/*
2	FUSE: Filesystem in Userspace
3	Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
4
5	This program can be distributed under the terms of the GNU LGPLv2.
6	See the file COPYING.LIB.
7	*/
8
9	#include "config.h"
10	#include "mount_util.h"
11	#include <stdio.h>
12	#include <unistd.h>
13	#include <stdlib.h>
14	#include <string.h>
15	#include <dirent.h>
16	#include <errno.h>
17	#include <limits.h>
18	#include <mntent.h>
19	#include <sys/stat.h>
20	#include <sys/wait.h>
21	#include <sys/mount.h>
22	#include <sys/param.h>
23
24	static int mtab_needs_update(const char *mnt)
25	{
26	int res;
27	struct stat stbuf;
28
29	/* If mtab is within new mount, don't touch it */
30	if (strncmp(mnt, _PATH_MOUNTED, strlen(mnt)) == 0 &&
31	_PATH_MOUNTED[strlen(mnt)] == '/')
32	return 0;
33
34	/*
35	* Skip mtab update if /etc/mtab:
36	*
37	* - doesn't exist,
38	* - is a symlink,
39	* - is on a read-only filesystem.
40	*/
41	res = lstat(_PATH_MOUNTED, &stbuf);
42	if (res == -1) {
43	if (errno == ENOENT)
44	return 0;
45	} else {
46	if (S_ISLNK(stbuf.st_mode))
47	return 0;
48
49	res = access(_PATH_MOUNTED, W_OK);
50	if (res == -1 && errno == EROFS)
51	return 0;
52	}
53
54	return 1;
55	}
56
57	int fuse_mnt_add_mount(const char *progname, const char *fsname,
58	const char *mnt, const char *type, const char *opts)
59	{
60	int res;
61
62	if (!mtab_needs_update(mnt))
63	return 0;
64
65	res = fork();
66	if (res == -1) {
67	fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
68	return 0;
69	}
70	if (res == 0) {
71	char templ[] = "/tmp/fusermountXXXXXX";
72	char *tmp;
73
74	setuid(geteuid());
75
76	/*
77	* hide in a directory, where mount isn't able to resolve
78	* fsname as a valid path
79	*/
80	tmp = mkdtemp(templ);
81	if (!tmp) {
82	fprintf(stderr, "%s: failed to create temporary directory\n",
83	progname);
84	exit(1);
85	}
86	if (chdir(tmp)) {
87	fprintf(stderr, "%s: failed to chdir to %s: %s\n",
88	progname, tmp, strerror(errno));
89	exit(1);
90	}
91	rmdir(tmp);
92	execl("/bin/mount", "/bin/mount", "-i", "-f", "-t", type, "-o", opts,
93	fsname, mnt, NULL);
94	fprintf(stderr, "%s: failed to execute /bin/mount: %s\n", progname,
95	strerror(errno));
96	exit(1);
97	}
98	return 0;
99	}
100
101	int fuse_mnt_umount(const char *progname, const char *mnt, int lazy)
102	{
103	int res;
104	int status;
105
106	if (!mtab_needs_update(mnt)) {
107	res = umount2(mnt, lazy ? 2 : 0);
108	if (res == -1)
109	fprintf(stderr, "%s: failed to unmount %s: %s\n", progname,
110	mnt, strerror(errno));
111	return res;
112	}
113
114	res = fork();
115	if (res == -1) {
116	fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
117	return -1;
118	}
119	if (res == 0) {
120	setuid(geteuid());
121	execl("/bin/umount", "/bin/umount", "-i", mnt, lazy ? "-l" : NULL,
122	NULL);
123	fprintf(stderr, "%s: failed to execute /bin/umount: %s\n", progname,
124	strerror(errno));
125	exit(1);
126	}
127	res = waitpid(res, &status, 0);
128	if (res == -1) {
129	fprintf(stderr, "%s: waitpid: %s\n", progname, strerror(errno));
130	return -1;
131	}
132	if (status != 0)
133	return -1;
134
135	return 0;
136	}
137
138	char *fuse_mnt_resolve_path(const char *progname, const char *orig)
139	{
140	char buf[PATH_MAX];
141	char *copy;
142	char *dst;
143	char *end;
144	char *lastcomp;
145	const char *toresolv;
146
147	if (!orig[0]) {
148	fprintf(stderr, "%s: invalid mountpoint '%s'\n", progname, orig);
149	return NULL;
150	}
151
152	copy = strdup(orig);
153	if (copy == NULL) {
154	fprintf(stderr, "%s: failed to allocate memory\n", progname);
155	return NULL;
156	}
157
158	toresolv = copy;
159	lastcomp = NULL;
160	for (end = copy + strlen(copy) - 1; end > copy && *end == '/'; end --);
161	if (end[0] != '/') {
162	char *tmp;
163	end[1] = '\0';
164	tmp = strrchr(copy, '/');
165	if (tmp == NULL) {
166	lastcomp = copy;
167	toresolv = ".";
168	} else {
169	lastcomp = tmp + 1;
170	if (tmp == copy)
171	toresolv = "/";
172	}
173	if (strcmp(lastcomp, ".") == 0 || strcmp(lastcomp, "..") == 0) {
174	lastcomp = NULL;
175	toresolv = copy;
176	}
177	else if (tmp)
178	tmp[0] = '\0';
179	}
180	if (realpath(toresolv, buf) == NULL) {
181	fprintf(stderr, "%s: bad mount point %s: %s\n", progname, orig,
182	strerror(errno));
183	free(copy);
184	return NULL;
185	}
186	if (lastcomp == NULL)
187	dst = strdup(buf);
188	else {
189	dst = (char *) malloc(strlen(buf) + 1 + strlen(lastcomp) + 1);
190	if (dst) {
191	unsigned buflen = strlen(buf);
192	if (buflen && buf[buflen-1] == '/')
193	sprintf(dst, "%s%s", buf, lastcomp);
194	else
195	sprintf(dst, "%s/%s", buf, lastcomp);
196	}
197	}
198	free(copy);
199	if (dst == NULL)
200	fprintf(stderr, "%s: failed to allocate memory\n", progname);
201	return dst;
202	}
203
204	int fuse_mnt_check_fuseblk(void)
205	{
206	char buf[256];
207	FILE *f = fopen("/proc/filesystems", "r");
208	if (!f)
209	return 1;
210
211	while (fgets(buf, sizeof(buf), f))
212	if (strstr(buf, "fuseblk\n")) {
213	fclose(f);
214	return 1;
215	}
216
217	fclose(f);
218	return 0;
219	}
220