linux-kernel - Re: [PATCH 1/2] fs: add link restrictions

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Message-ID: <CAGXu5jL45EWVr9PfhF6vpb-PmHPZLOC9Dao_MKpjx2LBhbzKOg@mail.gmail.com>
Date:	Sun, 1 Jul 2012 18:26:38 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, Eric Paris <eparis@...hat.com>,
	Matthew Wilcox <matthew@....cx>,
	Doug Ledford <dledford@...hat.com>,
	Joe Korty <joe.korty@...r.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	David Howells <dhowells@...hat.com>,
	James Morris <james.l.morris@...cle.com>,
	linux-doc@...r.kernel.org,
	Dan Rosenberg <drosenberg@...curity.com>,
	kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 1/2] fs: add link restrictions

On Sun, Jul 1, 2012 at 5:43 PM, Kees Cook <keescook@...omium.org> wrote:
> On Sat, Jun 30, 2012 at 2:14 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
>> On Mon, Jun 25, 2012 at 02:05:26PM -0700, Kees Cook wrote:
>>> +                     err = may_follow_link(&link);
>>> +                     if (unlikely(err))
>>> +                             break;
>>
>> No.  This is definitely wrong - you are leaking dentries and vfsmount here.
>
> What should I do to avoid the leak? I thought it was avoiding the need
> to call put_link because it aborts before calling follow_link.

Does this need "path_put(&nd->path);" added to the abort case?

If so, is this also missing from follow_link()'s final "return error",
or is it the responsibility of dentry->d_inode->i_op->follow_link() to
have already called path_put()?

-Kees

-- 
Kees Cook
Chrome OS Security
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