mount_util.c
/*
FUSE: Filesystem in Userspace
Copyright (C) 2001-2007 Miklos Szeredi <miklos@szeredi.hu>
Architecture-independent mounting code.
This program can be distributed under the terms of the GNU LGPLv2.
See the file COPYING.LIB.
*/
#include "config.h"
#include "mount_util.h"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <paths.h>
#if !defined( __NetBSD__) && !defined(__FreeBSD__)
#include <mntent.h>
#else
#define IGNORE_MTAB
#endif
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/mount.h>
#include <sys/param.h>
#if defined(__NetBSD__) || defined(__FreeBSD__)
#define umount2(mnt, flags) unmount(mnt, (flags == 2) ? MNT_FORCE : 0)
#endif
#ifdef IGNORE_MTAB
#define mtab_needs_update(mnt) 0
#else
static int mtab_needs_update(const char *mnt)
{
int res;
struct stat stbuf;
/* If mtab is within new mount, don't touch it */
if (strncmp(mnt, _PATH_MOUNTED, strlen(mnt)) == 0 &&
_PATH_MOUNTED[strlen(mnt)] == '/')
return 0;
/*
* Skip mtab update if /etc/mtab:
*
* - doesn't exist,
* - is a symlink,
* - is on a read-only filesystem.
*/
res = lstat(_PATH_MOUNTED, &stbuf);
if (res == -1) {
if (errno == ENOENT)
return 0;
} else {
uid_t ruid;
int err;
if (S_ISLNK(stbuf.st_mode))
return 0;
ruid = getuid();
if (ruid != 0)
setreuid(0, -1);
res = access(_PATH_MOUNTED, W_OK);
err = (res == -1) ? errno : 0;
if (ruid != 0)
setreuid(ruid, -1);
if (err == EROFS)
return 0;
}
return 1;
}
#endif /* IGNORE_MTAB */
static int add_mount(const char *progname, const char *fsname,
const char *mnt, const char *type, const char *opts)
{
int res;
int status;
sigset_t blockmask;
sigset_t oldmask;
sigemptyset(&blockmask);
sigaddset(&blockmask, SIGCHLD);
res = sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
if (res == -1) {
fprintf(stderr, "%s: sigprocmask: %s\n", progname, strerror(errno));
return -1;
}
res = fork();
if (res == -1) {
fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
goto out_restore;
}
if (res == 0) {
char *env = NULL;
sigprocmask(SIG_SETMASK, &oldmask, NULL);
if(setuid(geteuid()) == -1) {
fprintf(stderr, "%s: setuid: %s\n", progname, strerror(errno));
res = -1;
goto out_restore;
}
execle("/bin/mount", "/bin/mount", "--no-canonicalize", "-i",
"-f", "-t", type, "-o", opts, fsname, mnt, NULL, &env);
fprintf(stderr, "%s: failed to execute /bin/mount: %s\n",
progname, strerror(errno));
exit(1);
}
res = waitpid(res, &status, 0);
if (res == -1)
fprintf(stderr, "%s: waitpid: %s\n", progname, strerror(errno));
if (status != 0)
res = -1;
out_restore:
sigprocmask(SIG_SETMASK, &oldmask, NULL);
return res;
}
int fuse_mnt_add_mount(const char *progname, const char *fsname,
const char *mnt, const char *type, const char *opts)
{
if (!mtab_needs_update(mnt))
return 0;
return add_mount(progname, fsname, mnt, type, opts);
}
static int exec_umount(const char *progname, const char *rel_mnt, int lazy)
{
int res;
int status;
sigset_t blockmask;
sigset_t oldmask;
sigemptyset(&blockmask);
sigaddset(&blockmask, SIGCHLD);
res = sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
if (res == -1) {
fprintf(stderr, "%s: sigprocmask: %s\n", progname, strerror(errno));
return -1;
}
res = fork();
if (res == -1) {
fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
goto out_restore;
}
if (res == 0) {
char *env = NULL;
sigprocmask(SIG_SETMASK, &oldmask, NULL);
if(setuid(geteuid()) == -1) {
fprintf(stderr, "%s: setuid: %s\n", progname, strerror(errno));
res = -1;
goto out_restore;
}
if (lazy) {
execle("/bin/umount", "/bin/umount", "-i", rel_mnt,
"-l", NULL, &env);
} else {
execle("/bin/umount", "/bin/umount", "-i", rel_mnt,
NULL, &env);
}
fprintf(stderr, "%s: failed to execute /bin/umount: %s\n",
progname, strerror(errno));
exit(1);
}
res = waitpid(res, &status, 0);
if (res == -1)
fprintf(stderr, "%s: waitpid: %s\n", progname, strerror(errno));
if (status != 0) {
res = -1;
}
out_restore:
sigprocmask(SIG_SETMASK, &oldmask, NULL);
return res;
}
int fuse_mnt_umount(const char *progname, const char *abs_mnt,
const char *rel_mnt, int lazy)
{
int res;
if (!mtab_needs_update(abs_mnt)) {
res = umount2(rel_mnt, lazy ? 2 : 0);
if (res == -1)
fprintf(stderr, "%s: failed to unmount %s: %s\n",
progname, abs_mnt, strerror(errno));
return res;
}
return exec_umount(progname, rel_mnt, lazy);
}
static int remove_mount(const char *progname, const char *mnt)
{
int res;
int status;
sigset_t blockmask;
sigset_t oldmask;
sigemptyset(&blockmask);
sigaddset(&blockmask, SIGCHLD);
res = sigprocmask(SIG_BLOCK, &blockmask, &oldmask);
if (res == -1) {
fprintf(stderr, "%s: sigprocmask: %s\n", progname, strerror(errno));
return -1;
}
res = fork();
if (res == -1) {
fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
goto out_restore;
}
if (res == 0) {
char *env = NULL;
sigprocmask(SIG_SETMASK, &oldmask, NULL);
if(setuid(geteuid()) == -1) {
fprintf(stderr, "%s: setuid: %s\n", progname, strerror(errno));
res = -1;
goto out_restore;
}
execle("/bin/umount", "/bin/umount", "--no-canonicalize", "-i",
"--fake", mnt, NULL, &env);
fprintf(stderr, "%s: failed to execute /bin/umount: %s\n",
progname, strerror(errno));
exit(1);
}
res = waitpid(res, &status, 0);
if (res == -1)
fprintf(stderr, "%s: waitpid: %s\n", progname, strerror(errno));
if (status != 0)
res = -1;
out_restore:
sigprocmask(SIG_SETMASK, &oldmask, NULL);
return res;
}
int fuse_mnt_remove_mount(const char *progname, const char *mnt)
{
if (!mtab_needs_update(mnt))
return 0;
return remove_mount(progname, mnt);
}
char *fuse_mnt_resolve_path(const char *progname, const char *orig)
{
char buf[PATH_MAX];
char *copy;
char *dst;
char *end;
char *lastcomp;
const char *toresolv;
if (!orig[0]) {
fprintf(stderr, "%s: invalid mountpoint '%s'\n", progname,
orig);
return NULL;
}
copy = strdup(orig);
if (copy == NULL) {
fprintf(stderr, "%s: failed to allocate memory\n", progname);
return NULL;
}
toresolv = copy;
lastcomp = NULL;
for (end = copy + strlen(copy) - 1; end > copy && *end == '/'; end --);
if (end[0] != '/') {
char *tmp;
end[1] = '\0';
tmp = strrchr(copy, '/');
if (tmp == NULL) {
lastcomp = copy;
toresolv = ".";
} else {
lastcomp = tmp + 1;
if (tmp == copy)
toresolv = "/";
}
if (strcmp(lastcomp, ".") == 0 || strcmp(lastcomp, "..") == 0) {
lastcomp = NULL;
toresolv = copy;
}
else if (tmp)
tmp[0] = '\0';
}
if (realpath(toresolv, buf) == NULL) {
fprintf(stderr, "%s: bad mount point %s: %s\n", progname, orig,
strerror(errno));
free(copy);
return NULL;
}
if (lastcomp == NULL)
dst = strdup(buf);
else {
dst = (char *) malloc(strlen(buf) + 1 + strlen(lastcomp) + 1);
if (dst) {
unsigned buflen = strlen(buf);
if (buflen && buf[buflen-1] == '/')
sprintf(dst, "%s%s", buf, lastcomp);
else
sprintf(dst, "%s/%s", buf, lastcomp);
}
}
free(copy);
if (dst == NULL)
fprintf(stderr, "%s: failed to allocate memory\n", progname);
return dst;
}
int fuse_mnt_check_fuseblk(void)
{
char buf[256];
FILE *f = fopen("/proc/filesystems", "r");
if (!f)
return 1;
while (fgets(buf, sizeof(buf), f))
if (strstr(buf, "fuseblk\n")) {
fclose(f);
return 1;
}
fclose(f);
return 0;
}
int fuse_mnt_parse_fuse_fd(const char *mountpoint)
{
int fd = -1;
int len = 0;
if (sscanf(mountpoint, "/dev/fd/%u%n", &fd, &len) == 1 &&
len == strlen(mountpoint)) {
return fd;
}
return -1;
}