fs: Add a missing permission check to do_umount

Accessing do_remount_sb should require global CAP_SYS_ADMIN, but only one of the two call sites was appropriately protected. Fixes CVE-2014-7975. Signed-off-by: Andy Lutomirski <luto@amacapital.net>
git-mirror · Oct 8, 2014 · a1480dc · a1480dc
1 parent bfe01a5
commit a1480dc
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/fs/namespace.c b/fs/namespace.c
@@ -1356,6 +1356,8 @@ static int do_umount(struct mount *mnt, int flags)
 		 * Special case for "unmounting" root ...
 		 * we just try to remount it readonly.
 		 */
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
 		down_write(&sb->s_umount);
 		if (!(sb->s_flags & MS_RDONLY))
 			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);