397 lines
9.1 KiB
C
397 lines
9.1 KiB
C
/*
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* ismounted.c --- Check to see if the filesystem was mounted
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*
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* Copyright (C) 1995,1996,1997,1998,1999,2000,2008 Theodore Ts'o.
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*
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* This file may be redistributed under the terms of the GNU Public
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* License.
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <fcntl.h>
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#ifdef HAVE_MNTENT_H
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#include <mntent.h>
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#endif
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#include <string.h>
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#include <sys/stat.h>
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#include <ctype.h>
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#include <sys/param.h>
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#ifndef __linux__
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# ifdef HAVE_SYS_UCRED_H
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# include <sys/ucred.h>
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# endif
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# ifdef HAVE_SYS_MOUNT_H
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# include <sys/mount.h>
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# endif
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#endif
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#include "pathnames.h"
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#include "strutils.h"
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#include "ismounted.h"
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#include "c.h"
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#ifdef __linux__
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# include "loopdev.h"
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#endif
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#ifdef HAVE_MNTENT_H
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/*
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* Helper function which checks a file in /etc/mtab format to see if a
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* filesystem is mounted. Returns an error if the file doesn't exist
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* or can't be opened.
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*/
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static int check_mntent_file(const char *mtab_file, const char *file,
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int *mount_flags, char *mtpt, int mtlen)
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{
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struct mntent *mnt;
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struct stat st_buf;
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int retval = 0;
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dev_t file_dev=0, file_rdev=0;
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ino_t file_ino=0;
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FILE *f;
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int fd;
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*mount_flags = 0;
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if ((f = setmntent (mtab_file, "r")) == NULL)
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return errno;
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if (stat(file, &st_buf) == 0) {
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if (S_ISBLK(st_buf.st_mode)) {
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#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
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file_rdev = st_buf.st_rdev;
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#endif /* __GNU__ */
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} else {
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file_dev = st_buf.st_dev;
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file_ino = st_buf.st_ino;
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}
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}
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while ((mnt = getmntent (f)) != NULL) {
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if (mnt->mnt_fsname[0] != '/')
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continue;
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if (strcmp(file, mnt->mnt_fsname) == 0)
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break;
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if (stat(mnt->mnt_fsname, &st_buf) != 0)
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continue;
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if (S_ISBLK(st_buf.st_mode)) {
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#ifndef __GNU__
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if (file_rdev && file_rdev == st_buf.st_rdev)
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break;
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#ifdef __linux__
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/* maybe the file is loopdev backing file */
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if (file_dev
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&& major(st_buf.st_rdev) == LOOPDEV_MAJOR
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&& loopdev_is_used(mnt->mnt_fsname, file, 0, 0, 0))
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break;
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#endif /* __linux__ */
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#endif /* __GNU__ */
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} else {
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if (file_dev && ((file_dev == st_buf.st_dev) &&
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(file_ino == st_buf.st_ino)))
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break;
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}
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}
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if (mnt == NULL) {
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#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
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/*
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* Do an extra check to see if this is the root device. We
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* can't trust /etc/mtab, and /proc/mounts will only list
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* /dev/root for the root filesystem. Argh. Instead we
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* check if the given device has the same major/minor number
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* as the device that the root directory is on.
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*/
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if (file_rdev && stat("/", &st_buf) == 0 &&
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st_buf.st_dev == file_rdev) {
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*mount_flags = MF_MOUNTED;
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if (mtpt)
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xstrncpy(mtpt, "/", mtlen);
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goto is_root;
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}
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#endif /* __GNU__ */
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goto errout;
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}
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#ifndef __GNU__ /* The GNU hurd is deficient; what else is new? */
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/* Validate the entry in case /etc/mtab is out of date */
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/*
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* We need to be paranoid, because some broken distributions
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* (read: Slackware) don't initialize /etc/mtab before checking
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* all of the non-root filesystems on the disk.
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*/
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if (stat(mnt->mnt_dir, &st_buf) < 0) {
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retval = errno;
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if (retval == ENOENT) {
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#ifdef DEBUG
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printf("Bogus entry in %s! (%s does not exist)\n",
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mtab_file, mnt->mnt_dir);
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#endif /* DEBUG */
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retval = 0;
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}
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goto errout;
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}
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if (file_rdev && (st_buf.st_dev != file_rdev)) {
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#ifdef DEBUG
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printf("Bogus entry in %s! (%s not mounted on %s)\n",
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mtab_file, file, mnt->mnt_dir);
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#endif /* DEBUG */
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goto errout;
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}
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#endif /* __GNU__ */
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*mount_flags = MF_MOUNTED;
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#ifdef MNTOPT_RO
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/* Check to see if the ro option is set */
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if (hasmntopt(mnt, MNTOPT_RO))
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*mount_flags |= MF_READONLY;
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#endif
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if (mtpt)
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xstrncpy(mtpt, mnt->mnt_dir, mtlen);
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/*
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* Check to see if we're referring to the root filesystem.
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* If so, do a manual check to see if we can open /etc/mtab
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* read/write, since if the root is mounted read/only, the
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* contents of /etc/mtab may not be accurate.
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*/
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if (!strcmp(mnt->mnt_dir, "/")) {
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is_root:
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#define TEST_FILE "/.ismount-test-file"
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*mount_flags |= MF_ISROOT;
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fd = open(TEST_FILE, O_RDWR|O_CREAT|O_CLOEXEC, 0600);
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if (fd < 0) {
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if (errno == EROFS)
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*mount_flags |= MF_READONLY;
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} else
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close(fd);
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(void) unlink(TEST_FILE);
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}
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retval = 0;
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errout:
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endmntent (f);
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return retval;
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}
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static int check_mntent(const char *file, int *mount_flags,
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char *mtpt, int mtlen)
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{
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int retval;
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#ifdef DEBUG
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retval = check_mntent_file("/tmp/mtab", file, mount_flags,
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mtpt, mtlen);
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if (retval == 0)
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return 0;
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#endif /* DEBUG */
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#ifdef __linux__
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retval = check_mntent_file("/proc/mounts", file, mount_flags,
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mtpt, mtlen);
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if (retval == 0 && (*mount_flags != 0))
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return 0;
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if (access("/proc/mounts", R_OK) == 0) {
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*mount_flags = 0;
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return retval;
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}
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#endif /* __linux__ */
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#if defined(MOUNTED) || defined(_PATH_MOUNTED)
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#ifndef MOUNTED
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#define MOUNTED _PATH_MOUNTED
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#endif /* MOUNTED */
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retval = check_mntent_file(MOUNTED, file, mount_flags, mtpt, mtlen);
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return retval;
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#else
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*mount_flags = 0;
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return 0;
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#endif /* defined(MOUNTED) || defined(_PATH_MOUNTED) */
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}
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#else
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#if defined(HAVE_GETMNTINFO)
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static int check_getmntinfo(const char *file, int *mount_flags,
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char *mtpt, int mtlen)
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{
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struct statfs *mp;
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int len, n;
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const char *s1;
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char *s2;
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n = getmntinfo(&mp, MNT_NOWAIT);
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if (n == 0)
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return errno;
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len = sizeof(_PATH_DEV) - 1;
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s1 = file;
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if (strncmp(_PATH_DEV, s1, len) == 0)
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s1 += len;
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*mount_flags = 0;
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while (--n >= 0) {
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s2 = mp->f_mntfromname;
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if (strncmp(_PATH_DEV, s2, len) == 0) {
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s2 += len - 1;
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*s2 = 'r';
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}
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if (strcmp(s1, s2) == 0 || strcmp(s1, &s2[1]) == 0) {
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*mount_flags = MF_MOUNTED;
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break;
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}
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++mp;
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}
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if (mtpt && n >= 0)
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xstrncpy(mtpt, mp->f_mntonname, mtlen);
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return 0;
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}
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#endif /* HAVE_GETMNTINFO */
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#endif /* HAVE_MNTENT_H */
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/*
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* Check to see if we're dealing with the swap device.
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*/
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static int is_swap_device(const char *file)
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{
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FILE *f;
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char buf[1024], *cp;
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dev_t file_dev;
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struct stat st_buf;
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int ret = 0;
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file_dev = 0;
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#ifndef __GNU__ /* The GNU hurd is broken with respect to stat devices */
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if ((stat(file, &st_buf) == 0) &&
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S_ISBLK(st_buf.st_mode))
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file_dev = st_buf.st_rdev;
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#endif /* __GNU__ */
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if (!(f = fopen("/proc/swaps", "r" UL_CLOEXECSTR)))
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return 0;
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/* Skip the first line */
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if (!fgets(buf, sizeof(buf), f))
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goto leave;
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if (*buf && strncmp(buf, "Filename\t", 9) != 0)
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/* Linux <=2.6.19 contained a bug in the /proc/swaps
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* code where the header would not be displayed
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*/
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goto valid_first_line;
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while (fgets(buf, sizeof(buf), f)) {
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valid_first_line:
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if ((cp = strchr(buf, ' ')) != NULL)
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*cp = 0;
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if ((cp = strchr(buf, '\t')) != NULL)
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*cp = 0;
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if (strcmp(buf, file) == 0) {
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ret++;
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break;
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}
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#ifndef __GNU__
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if (file_dev && (stat(buf, &st_buf) == 0) &&
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S_ISBLK(st_buf.st_mode) &&
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file_dev == st_buf.st_rdev) {
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ret++;
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break;
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}
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#endif /* __GNU__ */
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}
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leave:
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fclose(f);
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return ret;
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}
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/*
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* check_mount_point() determines if the device is mounted or otherwise
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* busy, and fills in mount_flags with one or more of the following flags:
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* MF_MOUNTED, MF_ISROOT, MF_READONLY, MF_SWAP, and MF_BUSY. If mtpt is
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* non-NULL, the directory where the device is mounted is copied to where mtpt
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* is pointing, up to mtlen characters.
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*/
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#ifdef __TURBOC__
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#pragma argsused
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#endif
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int check_mount_point(const char *device, int *mount_flags,
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char *mtpt, int mtlen)
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{
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int retval = 0;
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if (is_swap_device(device)) {
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*mount_flags = MF_MOUNTED | MF_SWAP;
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if (mtpt && mtlen)
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xstrncpy(mtpt, "[SWAP]", mtlen);
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} else {
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#ifdef HAVE_MNTENT_H
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retval = check_mntent(device, mount_flags, mtpt, mtlen);
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#else
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#ifdef HAVE_GETMNTINFO
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retval = check_getmntinfo(device, mount_flags, mtpt, mtlen);
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#else
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#ifdef __GNUC__
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#warning "Can't use getmntent or getmntinfo to check for mounted filesystems!"
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#endif
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*mount_flags = 0;
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#endif /* HAVE_GETMNTINFO */
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#endif /* HAVE_MNTENT_H */
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}
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if (retval)
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return retval;
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#ifdef __linux__ /* This only works on Linux 2.6+ systems */
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{
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struct stat st_buf;
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int fd;
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if ((stat(device, &st_buf) != 0) ||
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!S_ISBLK(st_buf.st_mode))
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return 0;
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fd = open(device, O_RDONLY|O_EXCL|O_CLOEXEC|O_NONBLOCK);
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if (fd < 0) {
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if (errno == EBUSY)
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*mount_flags |= MF_BUSY;
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} else
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close(fd);
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}
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#endif
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return 0;
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}
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int is_mounted(const char *file)
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{
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int retval;
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int mount_flags = 0;
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retval = check_mount_point(file, &mount_flags, NULL, 0);
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if (retval)
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return 0;
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return mount_flags & MF_MOUNTED;
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}
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#ifdef TEST_PROGRAM_ISMOUNTED
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int main(int argc, char **argv)
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{
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int flags = 0;
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char devname[PATH_MAX];
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if (argc < 2) {
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fprintf(stderr, "Usage: %s device\n", argv[0]);
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return EXIT_FAILURE;
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}
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if (check_mount_point(argv[1], &flags, devname, sizeof(devname)) == 0 &&
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(flags & MF_MOUNTED)) {
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if (flags & MF_SWAP)
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printf("used swap device\n");
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else
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printf("mounted on %s\n", devname);
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return EXIT_SUCCESS;
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}
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printf("not mounted\n");
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return EXIT_FAILURE;
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}
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#endif /* DEBUG */
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