summaryrefslogtreecommitdiffstats
path: root/libblkid/lib/ismounted.c
blob: 8099bd7d5436e13cfbf2f08d2e0c9ef62aba4f4d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
/*
 * ismounted.c --- Check to see if the filesystem was mounted
 *
 * Copyright (C) 1995,1996,1997,1998,1999,2000,2008 Theodore Ts'o.
 *
 * This file may be redistributed under the terms of the GNU Public
 * License.
 */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#ifdef HAVE_MNTENT_H
#include <mntent.h>
#endif
#include <string.h>
#include <sys/stat.h>
#include <ctype.h>
#include <sys/param.h>
#ifdef __APPLE__
#include <sys/ucred.h>
#include <sys/mount.h>
#endif

#include "pathnames.h"
#include "ismounted.h"
#include "c.h"
#ifdef __linux__
# include "loopdev.h"
#endif



#ifdef HAVE_MNTENT_H
/*
 * Helper function which checks a file in /etc/mtab format to see if a
 * filesystem is mounted.  Returns an error if the file doesn't exist
 * or can't be opened.
 */
static int check_mntent_file(const char *mtab_file, const char *file,
				   int *mount_flags, char *mtpt, int mtlen)
{
	struct mntent	*mnt;
	struct stat	st_buf;
	int		retval = 0;
	dev_t		file_dev=0, file_rdev=0;
	ino_t		file_ino=0;
	FILE		*f;
	int		fd;

	*mount_flags = 0;
	if ((f = setmntent (mtab_file, "r")) == NULL)
		return errno;

	if (stat(file, &st_buf) == 0) {
		if (S_ISBLK(st_buf.st_mode)) {
#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
			file_rdev = st_buf.st_rdev;
#endif	/* __GNU__ */
		} else {
			file_dev = st_buf.st_dev;
			file_ino = st_buf.st_ino;
		}
	}

	while ((mnt = getmntent (f)) != NULL) {
		if (mnt->mnt_fsname[0] != '/')
			continue;
		if (strcmp(file, mnt->mnt_fsname) == 0)
			break;
		if (stat(mnt->mnt_fsname, &st_buf) != 0)
			continue;

		if (S_ISBLK(st_buf.st_mode)) {
#ifndef __GNU__
			if (file_rdev && file_rdev == st_buf.st_rdev)
				break;
#ifdef __linux__
			/* maybe the file is loopdev backing file */
			if (file_dev
			    && major(st_buf.st_rdev) == LOOPDEV_MAJOR
			    && loopdev_is_used(mnt->mnt_fsname, file, 0, 0))
				break;
#endif /* __linux__ */
#endif	/* __GNU__ */
		} else {
			if (file_dev && ((file_dev == st_buf.st_dev) &&
					 (file_ino == st_buf.st_ino)))
				break;
		}
	}

	if (mnt == NULL) {
#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
		/*
		 * Do an extra check to see if this is the root device.  We
		 * can't trust /etc/mtab, and /proc/mounts will only list
		 * /dev/root for the root filesystem.  Argh.  Instead we
		 * check if the given device has the same major/minor number
		 * as the device that the root directory is on.
		 */
		if (file_rdev && stat("/", &st_buf) == 0 &&
		    st_buf.st_dev == file_rdev) {
			*mount_flags = MF_MOUNTED;
			if (mtpt)
				strncpy(mtpt, "/", mtlen);
			goto is_root;
		}
#endif	/* __GNU__ */
		goto errout;
	}
#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
	/* Validate the entry in case /etc/mtab is out of date */
	/*
	 * We need to be paranoid, because some broken distributions
	 * (read: Slackware) don't initialize /etc/mtab before checking
	 * all of the non-root filesystems on the disk.
	 */
	if (stat(mnt->mnt_dir, &st_buf) < 0) {
		retval = errno;
		if (retval == ENOENT) {
#ifdef DEBUG
			printf("Bogus entry in %s!  (%s does not exist)\n",
			       mtab_file, mnt->mnt_dir);
#endif /* DEBUG */
			retval = 0;
		}
		goto errout;
	}
	if (file_rdev && (st_buf.st_dev != file_rdev)) {
#ifdef DEBUG
		printf("Bogus entry in %s!  (%s not mounted on %s)\n",
		       mtab_file, file, mnt->mnt_dir);
#endif /* DEBUG */
		goto errout;
	}
#endif /* __GNU__ */
	*mount_flags = MF_MOUNTED;

#ifdef MNTOPT_RO
	/* Check to see if the ro option is set */
	if (hasmntopt(mnt, MNTOPT_RO))
		*mount_flags |= MF_READONLY;
#endif

	if (mtpt)
		strncpy(mtpt, mnt->mnt_dir, mtlen);
	/*
	 * Check to see if we're referring to the root filesystem.
	 * If so, do a manual check to see if we can open /etc/mtab
	 * read/write, since if the root is mounted read/only, the
	 * contents of /etc/mtab may not be accurate.
	 */
	if (!strcmp(mnt->mnt_dir, "/")) {
is_root:
#define TEST_FILE "/.ismount-test-file"
		*mount_flags |= MF_ISROOT;
		fd = open(TEST_FILE, O_RDWR|O_CREAT|O_CLOEXEC, 0600);
		if (fd < 0) {
			if (errno == EROFS)
				*mount_flags |= MF_READONLY;
		} else
			close(fd);
		(void) unlink(TEST_FILE);
	}
	retval = 0;
errout:
	endmntent (f);
	return retval;
}

static int check_mntent(const char *file, int *mount_flags,
			      char *mtpt, int mtlen)
{
	int	retval;

#ifdef DEBUG
	retval = check_mntent_file("/tmp/mtab", file, mount_flags,
				   mtpt, mtlen);
	if (retval == 0)
		return 0;
#endif /* DEBUG */
#ifdef __linux__
	retval = check_mntent_file("/proc/mounts", file, mount_flags,
				   mtpt, mtlen);
	if (retval == 0 && (*mount_flags != 0))
		return 0;
	if (access("/proc/mounts", R_OK) == 0) {
		*mount_flags = 0;
		return retval;
	}
#endif /* __linux__ */
#if defined(MOUNTED) || defined(_PATH_MOUNTED)
#ifndef MOUNTED
#define MOUNTED _PATH_MOUNTED
#endif /* MOUNTED */
	retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
	return retval;
#else
	*mount_flags = 0;
	return 0;
#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
}

#else
#if defined(HAVE_GETMNTINFO)

static int check_getmntinfo(const char *file, int *mount_flags,
				  char *mtpt, int mtlen)
{
	struct statfs *mp;
        int    len, n;
        const  char   *s1;
	char	*s2;

        n = getmntinfo(&mp, MNT_NOWAIT);
        if (n == 0)
		return errno;

        len = sizeof(_PATH_DEV) - 1;
        s1 = file;
        if (strncmp(_PATH_DEV, s1, len) == 0)
                s1 += len;

	*mount_flags = 0;
        while (--n >= 0) {
                s2 = mp->f_mntfromname;
                if (strncmp(_PATH_DEV, s2, len) == 0) {
                        s2 += len - 1;
                        *s2 = 'r';
                }
                if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
			*mount_flags = MF_MOUNTED;
			break;
		}
                ++mp;
	}
	if (mtpt)
		strncpy(mtpt, mp->f_mntonname, mtlen);
	return 0;
}
#endif /* HAVE_GETMNTINFO */
#endif /* HAVE_MNTENT_H */

/*
 * Check to see if we're dealing with the swap device.
 */
static int is_swap_device(const char *file)
{
	FILE		*f;
	char		buf[1024], *cp;
	dev_t		file_dev;
	struct stat	st_buf;
	int		ret = 0;

	file_dev = 0;
#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
	if ((stat(file, &st_buf) == 0) &&
	    S_ISBLK(st_buf.st_mode))
		file_dev = st_buf.st_rdev;
#endif	/* __GNU__ */

	if (!(f = fopen("/proc/swaps", "r")))
		return 0;
	/* Skip the first line */
	if (!fgets(buf, sizeof(buf), f))
		goto leave;
	if (*buf && strncmp(buf, "Filename\t", 9))
		/* Linux <=2.6.19 contained a bug in the /proc/swaps
		 * code where the header would not be displayed
		 */
		goto valid_first_line;

	while (fgets(buf, sizeof(buf), f)) {
valid_first_line:
		if ((cp = strchr(buf, ' ')) != NULL)
			*cp = 0;
		if ((cp = strchr(buf, '\t')) != NULL)
			*cp = 0;
		if (strcmp(buf, file) == 0) {
			ret++;
			break;
		}
#ifndef __GNU__
		if (file_dev && (stat(buf, &st_buf) == 0) &&
		    S_ISBLK(st_buf.st_mode) &&
		    file_dev == st_buf.st_rdev) {
			ret++;
			break;
		}
#endif	/* __GNU__ */
	}

leave:
	fclose(f);
	return ret;
}


/*
 * check_mount_point() fills determines if the device is mounted or otherwise
 * busy, and fills in mount_flags with one or more of the following flags:
 * MF_MOUNTED, MF_ISROOT, MF_READONLY, MF_SWAP, and MF_BUSY.  If mtpt is
 * non-NULL, the directory where the device is mounted is copied to where mtpt
 * is pointing, up to mtlen characters.
 */
#ifdef __TURBOC__
 #pragma argsused
#endif
int check_mount_point(const char *device, int *mount_flags,
				  char *mtpt, int mtlen)
{
	struct stat	st_buf;
	int	retval = 0;
	int		fd;

	if (is_swap_device(device)) {
		*mount_flags = MF_MOUNTED | MF_SWAP;
		if (mtpt && mtlen)
			strncpy(mtpt, "[SWAP]", mtlen);
	} else {
#ifdef HAVE_MNTENT_H
		retval = check_mntent(device, mount_flags, mtpt, mtlen);
#else
#ifdef HAVE_GETMNTINFO
		retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
#else
#ifdef __GNUC__
 #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
#endif
		*mount_flags = 0;
#endif /* HAVE_GETMNTINFO */
#endif /* HAVE_MNTENT_H */
	}
	if (retval)
		return retval;

#ifdef __linux__ /* This only works on Linux 2.6+ systems */
	if ((stat(device, &st_buf) != 0) ||
	    !S_ISBLK(st_buf.st_mode))
		return 0;
	fd = open(device, O_RDONLY|O_EXCL|O_CLOEXEC);
	if (fd < 0) {
		if (errno == EBUSY)
			*mount_flags |= MF_BUSY;
	} else
		close(fd);
#endif

	return 0;
}

int is_mounted(const char *file)
{
	int	retval;
	int	mount_flags = 0;

	retval = check_mount_point(file, &mount_flags, NULL, 0);
	if (retval)
		return 0;
	return mount_flags & MF_MOUNTED;
}

#ifdef TEST_PROGRAM
int main(int argc, char **argv)
{
	int flags = 0;
	char devname[PATH_MAX];

	if (argc < 2) {
		fprintf(stderr, "Usage: %s device\n", argv[0]);
		return EXIT_FAILURE;
	}

	if (check_mount_point(argv[1], &flags, devname, sizeof(devname)) == 0 &&
	    (flags & MF_MOUNTED)) {
		if (flags & MF_SWAP)
			printf("used swap device\n");
		else
			printf("mounted on %s\n", devname);
		return EXIT_SUCCESS;
	}

	printf("not mounted\n");
	return EXIT_FAILURE;
}
#endif /* DEBUG */