mount: consolidate permission checks

... and ask for global CAP_SYS_ADMIN only for superblock-level remounts

Signed-off-by: Al Viro <[e-mail]>

fs/namespace.c

···
 
 #endif
 
-static int mount_is_safe(struct path *path)
-{
-	if (may_mount())
-		return 0;
-	return -EPERM;
-#ifdef notyet
-	if (S_ISLNK(path->dentry->d_inode->i_mode))
-		return -EPERM;
-	if (path->dentry->d_inode->i_mode & S_ISVTX) {
-		if (current_uid() != path->dentry->d_inode->i_uid)
-			return -EPERM;
-	}
-	if (inode_permission(path->dentry->d_inode, MAY_WRITE))
-		return -EPERM;
-	return 0;
-#endif
-}
-
 static bool mnt_ns_loop(struct path *path)
 {
 	/* Could bind mounting the mount namespace inode cause a
···
 	int type;
 	int err = 0;
 
-	if (!may_mount())
-		return -EPERM;
-
 	if (path->dentry != path->mnt->mnt_root)
 		return -EINVAL;
 
···
 	LIST_HEAD(umount_list);
 	struct path old_path;
 	struct mount *mnt = NULL, *old;
-	int err = mount_is_safe(path);
-	if (err)
-		return err;
+	int err;
 	if (!old_name || !*old_name)
 		return -EINVAL;
 	err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
···
 	struct super_block *sb = path->mnt->mnt_sb;
 	struct mount *mnt = real_mount(path->mnt);
 
-	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
 	if (!check_mnt(mnt))
 		return -EINVAL;
 
···
 	down_write(&sb->s_umount);
 	if (flags & MS_BIND)
 		err = change_mount_flags(path->mnt, flags);
+	else if (!capable(CAP_SYS_ADMIN))
+		err = -EPERM;
 	else
 		err = do_remount_sb(sb, flags, data, 0);
 	if (!err) {
···
 	struct path old_path, parent_path;
 	struct mount *p;
 	struct mount *old;
-	int err = 0;
-	if (!may_mount())
-		return -EPERM;
+	int err;
 	if (!old_name || !*old_name)
 		return -EINVAL;
 	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
···
 
 	if (!fstype)
 		return -EINVAL;
-
-	if (!may_mount())
-		return -EPERM;
 
 	type = get_fs_type(fstype);
 	if (!type)
···
 				   type_page, flags, data_page);
 	if (retval)
 		goto dput_out;
+
+	if (!may_mount())
+		return -EPERM;
 
 	/* Default to relatime unless overriden */
 	if (!(flags & MS_NOATIME))