commit 2368077223fa5800cf88659c9c57a7f6517f3fad
Author: Karel Zak <kzak@redhat.com>
Date: Tue Sep 11 14:35:34 2007 +0200
mount: prevent loop mounting the same file twice
The mount syscall prevents mounting the same device twice
to the same mountpoint. When loop mounting a file, for each
file a new loop device gets allocated, which prevents the detection
of loop mounting the same file to the same mountpoint twice.
The patch adds a check to prevent double mounts, if the same loopfile
is going to be mounted with the same offset to the same mountpoint.
Co-Author: Matthias Koenig <mkoenig@suse.de>
Signed-off-by: Matthias Koenig <mkoenig@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>
Index: util-linux-ng-2.13.1/mount/lomount.c
===================================================================
--- util-linux-ng-2.13.1.orig/mount/lomount.c
+++ util-linux-ng-2.13.1/mount/lomount.c
@@ -143,7 +143,7 @@ show_used_loop_devices (void) {
for (j = 0; j < SIZE(loop_formats); j++) {
for(i = 0; i < 256; i++) {
- sprintf(dev, loop_formats[j], i);
+ snprintf(dev, sizeof(dev), loop_formats[j], i);
if (stat (dev, &statbuf) == 0 && S_ISBLK(statbuf.st_mode)) {
fd = open (dev, O_RDONLY);
if (fd >= 0) {
@@ -169,6 +169,102 @@ show_used_loop_devices (void) {
#endif
+/* check if the loopfile is already associated with the same given
+ * parameters.
+ *
+ * returns: -1 error
+ * 0 unused
+ * 1 loop device already used
+ */
+static int
+is_associated(int dev, struct stat *file, unsigned long long offset)
+{
+ struct loop_info64 linfo64;
+ struct loop_info64 linfo;
+ int ret = 0;
+
+ if (ioctl(dev, LOOP_GET_STATUS64, &linfo64) == 0) {
+ if (file->st_dev == linfo64.lo_device &&
+ file->st_ino == linfo64.lo_inode &&
+ offset == linfo64.lo_offset)
+ ret = 1;
+ return ret;
+ }
+ if (ioctl(dev, LOOP_GET_STATUS, &linfo) == 0) {
+ if (file->st_dev == linfo.lo_device &&
+ file->st_ino == linfo.lo_inode &&
+ offset == linfo.lo_offset)
+ ret = 1;
+ return ret;
+ }
+
+ return errno == ENXIO ? 0 : -1;
+}
+
+/* check if the loop file is already used with the same given
+ * parameters. We check for device no, inode and offset.
+ * returns: associated devname or NULL
+ */
+char *
+loopfile_used (const char *filename, unsigned long long offset) {
+ char dev[20];
+ char *loop_formats[] = { "/dev/loop%d", "/dev/loop/%d" };
+ int i, j, fd;
+ struct stat devstat, filestat;
+ struct loop_info loopinfo;
+
+ if (stat(filename, &filestat) == -1) {
+ perror(filename);
+ return NULL;
+ }
+
+ for (j = 0; j < SIZE(loop_formats); j++) {
+ for(i = 0; i < 256; i++) {
+ snprintf(dev, sizeof(dev), loop_formats[j], i);
+ if (stat (dev, &devstat) == 0 && S_ISBLK(devstat.st_mode)) {
+ fd = open (dev, O_RDONLY);
+ if (fd >= 0) {
+ int res = 0;
+
+ if(ioctl (fd, LOOP_GET_STATUS, &loopinfo) == 0)
+ res = is_associated(fd, &filestat, offset);
+ close (fd);
+ if (res == 1)
+ return xstrdup(dev);
+ }
+ continue; /* continue trying as long as devices exist */
+ }
+ break;
+ }
+ }
+ return NULL;
+}
+
+int
+loopfile_used_with(char *devname, const char *filename, unsigned long long offset)
+{
+ struct stat statbuf;
+ int fd, ret;
+
+ if (!is_loop_device(devname))
+ return 0;
+
+ if (stat(filename, &statbuf) == -1) {
+ perror(filename);
+ return -1;
+ }
+
+ fd = open(devname, O_RDONLY);
+ if (fd == -1) {
+ perror(devname);
+ return -1;
+ }
+ ret = is_associated(fd, &statbuf, offset);
+
+ close(fd);
+ return ret;
+}
+
int
is_loop_device (const char *device) {
struct stat statbuf;
@@ -284,6 +380,16 @@ set_loop(const char *device, const char
char *filename;
char res_file[PATH_MAX+1];
+ if (verbose) {
+ char *xdev = loopfile_used(file, offset);
+
+ if (xdev) {
+ printf(_("warning: %s is already associated with %s\n"),
+ file, xdev);
+ free(xdev);
+ }
+ }
+
mode = (*loopro ? O_RDONLY : O_RDWR);
if ((ffd = open(file, mode)) < 0) {
if (!*loopro && errno == EROFS)
Index: util-linux-ng-2.13.1/mount/lomount.h
===================================================================
--- util-linux-ng-2.13.1.orig/mount/lomount.h
+++ util-linux-ng-2.13.1/mount/lomount.h
@@ -4,3 +4,6 @@ extern int set_loop(const char *, const
extern int del_loop(const char *);
extern int is_loop_device(const char *);
extern char * find_unused_loop_device(void);
+
+extern int loopfile_used_with(char *devname, const char *filename, unsigned long long offset);
+extern char *loopfile_used (const char *filename, unsigned long long offset);
Index: util-linux-ng-2.13.1/mount/mount.c
===================================================================
--- util-linux-ng-2.13.1.orig/mount/mount.c
+++ util-linux-ng-2.13.1/mount/mount.c
@@ -42,6 +42,7 @@
#include "mount_paths.h"
#include "env.h"
#include "nls.h"
+#include "realpath.h"
#define DO_PS_FIDDLING
@@ -833,9 +834,49 @@ suid_check(const char *spec, const char
*flags &= ~(MS_OWNER | MS_GROUP);
}
+/* Check, if there already exists a mounted loop device on the mountpoint node
+ * with the same parameters.
+ */
+static int
+is_mounted_same_loopfile(const char *node0, const char *loopfile, unsigned long long offset)
+{
+ struct mntentchn *mnt = NULL;
+ char node[PATH_MAX+1];
+ int res = 0;
+
+ myrealpath(node0, node, PATH_MAX);
+
+ /* Search for mountpoint node in mtab,
+ * procceed if any of these has the loop option set or
+ * the device is a loop device
+ */
+ mnt = getmntdirbackward(node, mnt);
+ if (!mnt) {
+ return 0;
+ }
+ for(; mnt && res == 0; mnt = getmntdirbackward(node, mnt)) {
+ char *p;
+
+ if (strncmp(mnt->m.mnt_fsname, "/dev/loop", 9) == 0)
+ res = loopfile_used_with((char *) mnt->m.mnt_fsname,
+ loopfile, offset);
+
+ else if ((p = strstr(mnt->m.mnt_opts, "loop="))) {
+ char *dev = xstrdup(p+5);
+ if ((p = strchr(dev, ',')))
+ *p = '\0';
+ res = loopfile_used_with(dev, loopfile, offset);
+ free(dev);
+ }
+ }
+
+ return res;
+}
+
static int
loop_check(const char **spec, const char **type, int *flags,
- int *loop, const char **loopdev, const char **loopfile) {
+ int *loop, const char **loopdev, const char **loopfile,
+ const char *node) {
int looptype;
unsigned long long offset;
@@ -876,6 +917,11 @@ loop_check(const char **spec, const char
offset = opt_offset ? strtoull(opt_offset, NULL, 0) : 0;
+ if (is_mounted_same_loopfile(node, *loopfile, offset)) {
+ error(_("mount: according to mtab %s is already mounted on %s as loop"), *loopfile, node);
+ return EX_FAIL;
+ }
+
do {
if (!*loopdev || !**loopdev)
*loopdev = find_unused_loop_device();
@@ -1061,7 +1107,7 @@ try_mount_one (const char *spec0, const
* stale assignments of files to loop devices. Nasty when used for
* encryption.
*/
- res = loop_check(&spec, &types, &flags, &loop, &loopdev, &loopfile);
+ res = loop_check(&spec, &types, &flags, &loop, &loopdev, &loopfile, node);
if (res)
goto out;
}