lib/ext2fs/ismounted.c

   1 /*
   2  * ismounted.c --- Check to see if the filesystem was mounted
   3  *
   4  * Copyright (C) 1995,1996,1997,1998,1999,2000 Theodore Ts'o.
   5  *
   6  * %Begin-Header%
   7  * This file may be redistributed under the terms of the GNU Library
   8  * General Public License, version 2.
   9  * %End-Header%
  10  */
  11
  12 /* define BSD_SOURCE to make sure we get the major() macro */
  13 #ifndef _BSD_SOURCE
  14 #define _BSD_SOURCE
  15 #endif
  16 #ifndef _DEFAULT_SOURCE
  17 #define _DEFAULT_SOURCE /* since glibc 2.20 _SVID_SOURCE is deprecated */
  18 #endif
  19
  20 #include "config.h"
  21 #include <stdio.h>
  22 #if HAVE_UNISTD_H
  23 #include <unistd.h>
  24 #endif
  25 #if HAVE_ERRNO_H
  26 #include <errno.h>
  27 #endif
  28 #include <fcntl.h>
  29 #ifdef HAVE_LINUX_FD_H
  30 #include <linux/fd.h>
  31 #endif
  32 #ifdef HAVE_LINUX_LOOP_H
  33 #include <linux/loop.h>
  34 #include <sys/ioctl.h>
  35 #ifdef HAVE_LINUX_MAJOR_H
  36 #include <linux/major.h>
  37 #endif /* HAVE_LINUX_MAJOR_H */
  38 #endif /* HAVE_LINUX_LOOP_H */
  39 #ifdef HAVE_MNTENT_H
  40 #include <mntent.h>
  41 #endif
  42 #ifdef HAVE_GETMNTINFO
  43 #include <paths.h>
  44 #include <sys/param.h>
  45 #include <sys/mount.h>
  46 #endif /* HAVE_GETMNTINFO */
  47 #include <string.h>
  48 #include <sys/stat.h>
  49 #if HAVE_SYS_TYPES_H
  50 #include <sys/types.h>
  51 #endif
  52 #ifdef HAVE_SYS_SYSMACROS_H
  53 #include <sys/sysmacros.h>
  54 #endif
  55
  56 #include "ext2_fs.h"
  57 #include "ext2fs.h"
  58
  59 #ifdef HAVE_SETMNTENT
  60 /*
  61  * Check to see if a regular file is mounted.
  62  * If /etc/mtab/ is a symlink of /proc/mounts, you will need the following check
  63  * because the name in /proc/mounts is a loopback device not a regular file.
  64  */
  65 static int check_loop_mounted(const char *mnt_fsname, dev_t mnt_rdev,
  66                                 dev_t file_dev, ino_t file_ino)
  67 {
  68 #if defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H)
  69         struct loop_info64 loopinfo = {0, };
  70         int loop_fd, ret;
  71
  72         if (major(mnt_rdev) == LOOP_MAJOR) {
  73                 loop_fd = open(mnt_fsname, O_RDONLY);
  74                 if (loop_fd < 0)
  75                         return -1;
  76
  77                 ret = ioctl(loop_fd, LOOP_GET_STATUS64, &loopinfo);
  78                 close(loop_fd);
  79                 if (ret < 0)
  80                         return -1;
  81
  82                 if (file_dev == loopinfo.lo_device &&
  83                                 file_ino == loopinfo.lo_inode)
  84                         return 1;
  85         }
  86 #endif /* defined(HAVE_LINUX_LOOP_H) && defined(HAVE_LINUX_MAJOR_H) */
  87         return 0;
  88 }
  89
  90 /*
  91  * Helper function which checks a file in /etc/mtab format to see if a
  92  * filesystem is mounted.  Returns an error if the file doesn't exist
  93  * or can't be opened.
  94  */
  95 static errcode_t check_mntent_file(const char *mtab_file, const char *file,
  96                                    int *mount_flags, char *mtpt, int mtlen)
  97 {
  98         struct mntent   *mnt;
  99         struct stat     st_buf;
 100         errcode_t       retval = 0;
 101         dev_t           file_dev=0, file_rdev=0;
 102         ino_t           file_ino=0;
 103         FILE            *f;
 104         int             fd;
 105
 106         *mount_flags = 0;
 107
 108         if ((f = setmntent (mtab_file, "r")) == NULL) {
 109                 if (errno == ENOENT) {
 110                         if (getenv("EXT2FS_NO_MTAB_OK"))
 111                                 return 0;
 112                         else
 113                                 return EXT2_ET_NO_MTAB_FILE;
 114                 }
 115                 return errno;
 116         }
 117         if (stat(file, &st_buf) == 0) {
 118                 if (S_ISBLK(st_buf.st_mode)) {
 119 #ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
 120                         file_rdev = st_buf.st_rdev;
 121 #endif  /* __GNU__ */
 122                 } else {
 123                         file_dev = st_buf.st_dev;
 124                         file_ino = st_buf.st_ino;
 125                 }
 126         }
 127         while ((mnt = getmntent (f)) != NULL) {
 128                 if (mnt->mnt_fsname[0] != '/')
 129                         continue;
 130                 if (strcmp(file, mnt->mnt_fsname) == 0)
 131                         break;
 132                 if (stat(mnt->mnt_fsname, &st_buf) == 0) {
 133                         if (S_ISBLK(st_buf.st_mode)) {
 134 #ifndef __GNU__
 135                                 if (file_rdev && (file_rdev == st_buf.st_rdev))
 136                                         break;
 137                                 if (check_loop_mounted(mnt->mnt_fsname,
 138                                                 st_buf.st_rdev, file_dev,
 139                                                 file_ino) == 1)
 140                                         break;
 141 #endif  /* __GNU__ */
 142                         } else {
 143                                 if (file_dev && ((file_dev == st_buf.st_dev) &&
 144                                                  (file_ino == st_buf.st_ino)))
 145                                         break;
 146                         }
 147                 }
 148         }
 149
 150         if (mnt == 0) {
 151 #ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
 152                 /*
 153                  * Do an extra check to see if this is the root device.  We
 154                  * can't trust /etc/mtab, and /proc/mounts will only list
 155                  * /dev/root for the root filesystem.  Argh.  Instead we
 156                  * check if the given device has the same major/minor number
 157                  * as the device that the root directory is on.
 158                  */
 159                 if (file_rdev && stat("/", &st_buf) == 0) {
 160                         if (st_buf.st_dev == file_rdev) {
 161                                 *mount_flags = EXT2_MF_MOUNTED;
 162                                 if (mtpt)
 163                                         strncpy(mtpt, "/", mtlen);
 164                                 goto is_root;
 165                         }
 166                 }
 167 #endif  /* __GNU__ */
 168                 goto errout;
 169         }
 170 #ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
 171         /* Validate the entry in case /etc/mtab is out of date */
 172         /*
 173          * We need to be paranoid, because some broken distributions
 174          * (read: Slackware) don't initialize /etc/mtab before checking
 175          * all of the non-root filesystems on the disk.
 176          */
 177         if (stat(mnt->mnt_dir, &st_buf) < 0) {
 178                 retval = errno;
 179                 if (retval == ENOENT) {
 180 #ifdef DEBUG
 181                         printf("Bogus entry in %s!  (%s does not exist)\n",
 182                                mtab_file, mnt->mnt_dir);
 183 #endif /* DEBUG */
 184                         retval = 0;
 185                 }
 186                 goto errout;
 187         }
 188         if (file_rdev && (st_buf.st_dev != file_rdev)) {
 189 #ifdef DEBUG
 190                 printf("Bogus entry in %s!  (%s not mounted on %s)\n",
 191                        mtab_file, file, mnt->mnt_dir);
 192 #endif /* DEBUG */
 193                 goto errout;
 194         }
 195 #endif /* __GNU__ */
 196         *mount_flags = EXT2_MF_MOUNTED;
 197
 198 #ifdef MNTOPT_RO
 199         /* Check to see if the ro option is set */
 200         if (hasmntopt(mnt, MNTOPT_RO))
 201                 *mount_flags |= EXT2_MF_READONLY;
 202 #endif
 203
 204         if (mtpt)
 205                 strncpy(mtpt, mnt->mnt_dir, mtlen);
 206         /*
 207          * Check to see if we're referring to the root filesystem.
 208          * If so, do a manual check to see if we can open /etc/mtab
 209          * read/write, since if the root is mounted read/only, the
 210          * contents of /etc/mtab may not be accurate.
 211          */
 212         if (!strcmp(mnt->mnt_dir, "/")) {
 213 is_root:
 214 #define TEST_FILE "/.ismount-test-file"
 215                 *mount_flags |= EXT2_MF_ISROOT;
 216                 fd = open(TEST_FILE, O_RDWR|O_CREAT, 0600);
 217                 if (fd < 0) {
 218                         if (errno == EROFS)
 219                                 *mount_flags |= EXT2_MF_READONLY;
 220                 } else
 221                         close(fd);
 222                 (void) unlink(TEST_FILE);
 223         }
 224         retval = 0;
 225 errout:
 226         endmntent (f);
 227         return retval;
 228 }
 229
 230 static errcode_t check_mntent(const char *file, int *mount_flags,
 231                               char *mtpt, int mtlen)
 232 {
 233         errcode_t       retval;
 234
 235 #ifdef DEBUG
 236         retval = check_mntent_file("/tmp/mtab", file, mount_flags,
 237                                    mtpt, mtlen);
 238         if (retval == 0)
 239                 return 0;
 240 #endif /* DEBUG */
 241 #ifdef __linux__
 242         retval = check_mntent_file("/proc/mounts", file, mount_flags,
 243                                    mtpt, mtlen);
 244         if (retval == 0 && (*mount_flags != 0))
 245                 return 0;
 246 #endif /* __linux__ */
 247 #if defined(MOUNTED) || defined(_PATH_MOUNTED)
 248 #ifndef MOUNTED
 249 #define MOUNTED _PATH_MOUNTED
 250 #endif /* MOUNTED */
 251         retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
 252         return retval;
 253 #else
 254         *mount_flags = 0;
 255         return 0;
 256 #endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
 257 }
 258
 259 #else
 260 #if defined(HAVE_GETMNTINFO)
 261
 262 static errcode_t check_getmntinfo(const char *file, int *mount_flags,
 263                                   char *mtpt, int mtlen)
 264 {
 265         struct statfs *mp;
 266         int    len, n;
 267         const  char   *s1;
 268         char    *s2;
 269
 270         n = getmntinfo(&mp, MNT_NOWAIT);
 271         if (n == 0)
 272                 return errno;
 273
 274         len = sizeof(_PATH_DEV) - 1;
 275         s1 = file;
 276         if (strncmp(_PATH_DEV, s1, len) == 0)
 277                 s1 += len;
 278
 279         *mount_flags = 0;
 280         while (--n >= 0) {
 281                 s2 = mp->f_mntfromname;
 282                 if (strncmp(_PATH_DEV, s2, len) == 0) {
 283                         s2 += len - 1;
 284                         *s2 = 'r';
 285                 }
 286                 if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
 287                         *mount_flags = EXT2_MF_MOUNTED;
 288                         break;
 289                 }
 290                 ++mp;
 291         }
 292         if (mtpt)
 293                 strncpy(mtpt, mp->f_mntonname, mtlen);
 294         return 0;
 295 }
 296 #endif /* HAVE_GETMNTINFO */
 297 #endif /* HAVE_SETMNTENT */
 298
 299 /*
 300  * Check to see if we're dealing with the swap device.
 301  */
 302 static int is_swap_device(const char *file)
 303 {
 304         FILE            *f;
 305         char            buf[1024], *cp;
 306         dev_t           file_dev;
 307         struct stat     st_buf;
 308         int             ret = 0;
 309
 310         file_dev = 0;
 311 #ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
 312         if ((stat(file, &st_buf) == 0) &&
 313             S_ISBLK(st_buf.st_mode))
 314                 file_dev = st_buf.st_rdev;
 315 #endif  /* __GNU__ */
 316
 317         if (!(f = fopen("/proc/swaps", "r")))
 318                 return 0;
 319         /* Skip the first line */
 320         if (!fgets(buf, sizeof(buf), f))
 321                 goto leave;
 322         if (*buf && strncmp(buf, "Filename\t", 9))
 323                 /* Linux <=2.6.19 contained a bug in the /proc/swaps
 324                  * code where the header would not be displayed
 325                  */
 326                 goto valid_first_line;
 327
 328         while (fgets(buf, sizeof(buf), f)) {
 329 valid_first_line:
 330                 if ((cp = strchr(buf, ' ')) != NULL)
 331                         *cp = 0;
 332                 if ((cp = strchr(buf, '\t')) != NULL)
 333                         *cp = 0;
 334                 if (strcmp(buf, file) == 0) {
 335                         ret++;
 336                         break;
 337                 }
 338 #ifndef __GNU__
 339                 if (file_dev && (stat(buf, &st_buf) == 0) &&
 340                     S_ISBLK(st_buf.st_mode) &&
 341                     file_dev == st_buf.st_rdev) {
 342                         ret++;
 343                         break;
 344                 }
 345 #endif  /* __GNU__ */
 346         }
 347
 348 leave:
 349         fclose(f);
 350         return ret;
 351 }
 352
 353
 354 /*
 355  * ext2fs_check_mount_point() fills determines if the device is
 356  * mounted or otherwise busy, and fills in mount_flags with one or
 357  * more of the following flags: EXT2_MF_MOUNTED, EXT2_MF_ISROOT,
 358  * EXT2_MF_READONLY, EXT2_MF_SWAP, and EXT2_MF_BUSY.  If mtpt is
 359  * non-NULL, the directory where the device is mounted is copied to
 360  * where mtpt is pointing, up to mtlen characters.
 361  */
 362 #ifdef __TURBOC__
 363  #pragma argsused
 364 #endif
 365 errcode_t ext2fs_check_mount_point(const char *device, int *mount_flags,
 366                                   char *mtpt, int mtlen)
 367 {
 368         errcode_t       retval = 0;
 369
 370         if (getenv("EXT2FS_PRETEND_RO_MOUNT")) {
 371                 *mount_flags = EXT2_MF_MOUNTED | EXT2_MF_READONLY;
 372                 if (getenv("EXT2FS_PRETEND_ROOTFS"))
 373                         *mount_flags = EXT2_MF_ISROOT;
 374                 return 0;
 375         }
 376         if (getenv("EXT2FS_PRETEND_RW_MOUNT")) {
 377                 *mount_flags = EXT2_MF_MOUNTED;
 378                 if (getenv("EXT2FS_PRETEND_ROOTFS"))
 379                         *mount_flags = EXT2_MF_ISROOT;
 380                 return 0;
 381         }
 382
 383         if (is_swap_device(device)) {
 384                 *mount_flags = EXT2_MF_MOUNTED | EXT2_MF_SWAP;
 385                 strncpy(mtpt, "<swap>", mtlen);
 386         } else {
 387 #ifdef HAVE_SETMNTENT
 388                 retval = check_mntent(device, mount_flags, mtpt, mtlen);
 389 #else
 390 #ifdef HAVE_GETMNTINFO
 391                 retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
 392 #else
 393 #ifdef __GNUC__
 394  #warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
 395 #endif
 396                 *mount_flags = 0;
 397 #endif /* HAVE_GETMNTINFO */
 398 #endif /* HAVE_SETMNTENT */
 399         }
 400         if (retval)
 401                 return retval;
 402
 403 #ifdef __linux__ /* This only works on Linux 2.6+ systems */
 404         {
 405                 struct stat st_buf;
 406
 407                 if (stat(device, &st_buf) == 0 && S_ISBLK(st_buf.st_mode)) {
 408                         int fd = open(device, O_RDONLY | O_EXCL);
 409
 410                         if (fd >= 0)
 411                                 close(fd);
 412                         else if (errno == EBUSY)
 413                                 *mount_flags |= EXT2_MF_BUSY;
 414                 }
 415         }
 416 #endif
 417
 418         return 0;
 419 }
 420
 421 /*
 422  * ext2fs_check_if_mounted() sets the mount_flags EXT2_MF_MOUNTED,
 423  * EXT2_MF_READONLY, and EXT2_MF_ROOT
 424  *
 425  */
 426 errcode_t ext2fs_check_if_mounted(const char *file, int *mount_flags)
 427 {
 428         return ext2fs_check_mount_point(file, mount_flags, NULL, 0);
 429 }
 430
 431 #ifdef DEBUG
 432 int main(int argc, char **argv)
 433 {
 434         int     retval, mount_flags;
 435         char    mntpt[80];
 436
 437         if (argc < 2) {
 438                 fprintf(stderr, "Usage: %s device\n", argv[0]);
 439                 exit(1);
 440         }
 441
 442         add_error_table(&et_ext2_error_table);
 443         mntpt[0] = 0;
 444         retval = ext2fs_check_mount_point(argv[1], &mount_flags,
 445                                           mntpt, sizeof(mntpt));
 446         if (retval) {
 447                 com_err(argv[0], retval,
 448                         "while calling ext2fs_check_if_mounted");
 449                 exit(1);
 450         }
 451         printf("Device %s reports flags %02x\n", argv[1], mount_flags);
 452         if (mount_flags & EXT2_MF_BUSY)
 453                 printf("\t%s is apparently in use.\n", argv[1]);
 454         if (mount_flags & EXT2_MF_MOUNTED)
 455                 printf("\t%s is mounted.\n", argv[1]);
 456         if (mount_flags & EXT2_MF_SWAP)
 457                 printf("\t%s is a swap device.\n", argv[1]);
 458         if (mount_flags & EXT2_MF_READONLY)
 459                 printf("\t%s is read-only.\n", argv[1]);
 460         if (mount_flags & EXT2_MF_ISROOT)
 461                 printf("\t%s is the root filesystem.\n", argv[1]);
 462         if (mntpt[0])
 463                 printf("\t%s is mounted on %s.\n", argv[1], mntpt);
 464         exit(0);
 465 }
 466 #endif /* DEBUG */