linux-kernel - Re: [REVIEW][PATCH 1/4] vfs: Don't allow overwriting mounts in the current mount namespace

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Message-ID: <20131103035406.GA8537@ZenIV.linux.org.uk>
Date:	Sun, 3 Nov 2013 03:54:06 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Miklos Szeredi <miklos@...redi.hu>,
	Andy Lutomirski <luto@...capital.net>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Rob Landley <rob@...dley.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthias Schniedermeyer <ms@...d.de>,
	Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [REVIEW][PATCH 1/4] vfs: Don't allow overwriting mounts in the
 current mount namespace

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?
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