From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
Subject: Re: [REVIEW][PATCH 1/4] vfs: Don't allow overwriting mounts in the
	current mount namespace
Date: Sun, 3 Nov 2013 03:54:06 +0000
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To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Cc: Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org>, Linux Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Kernel Mailing List <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Linux-Fsdevel <linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Matthias Schniedermeyer <ms-QGhoYOTWWTg@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
List-Id: containers.vger.kernel.org

On Tue, Oct 15, 2013 at 01:16:48PM -0700, Eric W. Biederman wrote:

>  int vfs_rmdir(struct inode *dir, struct dentry *dentry)
>  {
>  	int error = may_delete(dir, dentry, 1);
> @@ -3622,6 +3636,9 @@ retry:
>  		error = -ENOENT;
>  		goto exit3;
>  	}
> +	error = -EBUSY;
> +	if (covered(nd.path.mnt, dentry))
> +		goto exit3;

Ugh...  And it's not racy because of...?  IOW, what's to keep the return
value of covered() from getting obsolete just as it's being calculated,
let alone returned?