mount: allow loop suid umount

Addresses-Suse-Bug: #461732
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/mount/umount.c b/mount/umount.c
index 0468cb44964cc0866dbf28adbe3bc8831337f7a7..0e5934fd66f74ecdc59307ae0f22ca82cb319bd0 100644 (file)
--- a/mount/umount.c
+++ b/mount/umount.c
@@ -406,7 +406,7 @@ static int
 contains(const char *list, const char *s) {
        int n = strlen(s);
 
-       while (*list) {
+       while (list && *list) {
                if (strncmp(list, s, n) == 0 &&
                    (list[n] == 0 || list[n] == ','))
                        return 1;
@@ -423,7 +423,7 @@ get_value(const char *list, const char *s) {
        const char *t;
        int n = strlen(s);
 
-       while (*list) {
+       while (list && *list) {
                if (strncmp(list, s, n) == 0) {
                        s = t = list+n;
                        while (*s && *s != ',')
@@ -432,6 +432,43 @@ get_value(const char *list, const char *s) {
                }
                while (*list && *list++ != ',') ;
        }
+       return NULL;
+}
+
+/* check if @mc contains a loop device which is associated
+ * with the @file in fs
+ */
+static int
+is_valid_loop(struct mntentchn *mc, struct mntentchn *fs)
+{
+       unsigned long long offset = 0;
+       char *p;
+
+       /* check if it begins with /dev/loop */
+       if (strncmp(mc->m.mnt_fsname, "/dev/loop", 9))
+               return 0;
+
+       /* check for loop option in fstab */
+       if (!contains(fs->m.mnt_opts, "loop"))
+               return 0;
+
+       /* check for offset option in fstab */
+       p = get_value(fs->m.mnt_opts, "offset=");
+       if (p)
+               offset = strtoull(p, NULL, 10);
+
+       /* check association */
+       if (loopfile_used_with((char *) mc->m.mnt_fsname,
+                               fs->m.mnt_fsname, offset) == 1) {
+               if (verbose > 1)
+                       printf(_("device %s is associated with %s\n"),
+                              mc->m.mnt_fsname, fs->m.mnt_fsname);
+               return 1;
+       }
+
+       if (verbose > 1)
+               printf(_("device %s is not associated with %s\n"),
+                      mc->m.mnt_fsname, fs->m.mnt_fsname);
        return 0;
 }
 
@@ -516,12 +553,15 @@ umount_file (char *arg) {
                   the pair (dev,file) in fstab. */
                fs = getfs_by_devdir(mc->m.mnt_fsname, mc->m.mnt_dir);
                if (!fs) {
-                       if (!getfs_by_spec (file) && !getfs_by_dir (file))
+                       fs = getfs_by_dir(file);
+                       if (!fs && !getfs_by_spec(file))
                                die (2,
                                     _("umount: %s is not in the fstab "
                                       "(and you are not root)"),
                                     file);
-                       else
+
+                       /* spec could be a file which is loop mounted */
+                       if (fs && !is_valid_loop(mc, fs))
                                die (2, _("umount: %s mount disagrees with "
                                          "the fstab"), file);
                }