linux-kernel - Re: [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but the current mount namespace

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Message-ID: <20131008160601.GJ14242@tucsk.piliscsaba.szeredi.hu>
Date:	Tue, 8 Oct 2013 18:06:01 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	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>
Subject: Re: [RFC][PATCH 4/3] vfs: Allow rmdir to remove mounts in all but
 the current mount namespace

On Mon, Oct 07, 2013 at 03:25:17PM -0700, Eric W. Biederman wrote:
> Andy Lutomirski <luto@...capital.net> writes:
> 
> > On Mon, Oct 7, 2013 at 7:55 AM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
> >> "Serge E. Hallyn" <serge@...lyn.com> writes:
> >>
> >>> Quoting Eric W. Biederman (ebiederm@...ssion.com):
> >>>>
> >>>> Programs have been known to test for empty directories by attempting
> >>>> to remove them.  To keep from violating the principle of least
> >>>> surprise don't let directories the caller can see with someting
> >>>> mounted on them be deleted.
> >>>
> >>> Do you think we should do the same thing for over-mounted file at
> >>> vfs_unlink()?
> >>
> >> We easily could.

And for vfs_rename()?

I think the risks of changing behavior outweigh the benefits.  How many times
did you have to remove or rename a mounted file or directory?  It's very rarely
needed.

Thanks,
Miklos
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