From: Pavel Machek <pavel@ucw.cz>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Jan Kara <jack@suse.cz>, "J. Bruce Fields" <bfields@fieldses.org>,
"Serge E. Hallyn" <serue@us.ibm.com>,
kernel list <linux-kernel@vger.kernel.org>,
linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk,
jamie@shareable.org
Subject: Re: symlinks with permissions
Date: Sun, 25 Oct 2009 10:36:04 +0100 [thread overview]
Message-ID: <20091025093604.GA1501@ucw.cz> (raw)
In-Reply-To: <1256579869.8576.7.camel@heimdal.trondhjem.org>
On Mon 2009-10-26 13:57:49, Trond Myklebust wrote:
> On Mon, 2009-10-26 at 18:46 +0100, Jan Kara wrote:
> > That's what I'd think as well but it does not as I've just learned and
> > tested :) proc_pid_follow_link actually directly gives a dentry of the
> > target file without checking permissions on the way.
It is weider. That symlink even has permissions. Those are not
checked, either.
> I seem to remember that is deliberate, the point being that a symlink
> in /proc/*/fd/ may contain a path that refers to a private namespace.
Well, it is unexpected and mild security hole.
Part of the problem is that even if you have read-only
filedescriptor, you can upgrade it to read-write, even if path is
inaccessible to you.
So if someone passes you read-only filedescriptor, you can still write
to it.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2009-10-26 18:04 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-25 6:29 symlinks with permissions Pavel Machek
2009-10-26 16:31 ` Jan Kara
2009-10-26 16:57 ` Serge E. Hallyn
2009-10-26 17:36 ` J. Bruce Fields
2009-10-26 17:46 ` Jan Kara
2009-10-26 17:57 ` Trond Myklebust
2009-10-25 9:36 ` Pavel Machek [this message]
2009-10-26 18:22 ` Trond Myklebust
2009-10-27 8:11 ` Pavel Machek
2009-10-27 10:27 ` Jamie Lokier
2009-10-26 18:35 ` J. Bruce Fields
2009-10-28 4:15 ` Eric W. Biederman
2009-10-28 8:16 ` Pavel Machek
2009-10-28 11:25 ` Eric W. Biederman
2009-10-28 21:03 ` Pavel Machek
2009-10-29 2:20 ` Eric W. Biederman
2009-10-29 11:03 ` Pavel Machek
2009-10-29 16:23 ` Eric W. Biederman
2009-10-30 18:35 ` Pavel Machek
2009-10-30 20:37 ` Nick Bowler
2009-10-30 23:03 ` Eric W. Biederman
2009-10-31 2:30 ` Jamie Lokier
2009-10-28 16:34 ` Casey Schaufler
2009-10-28 19:44 ` Jamie Lokier
2009-10-28 21:06 ` Pavel Machek
2009-10-28 22:48 ` David Wagner
2009-10-29 4:13 ` Casey Schaufler
2009-10-29 7:53 ` David Wagner
2009-10-30 14:07 ` Pavel Machek
2009-10-31 4:09 ` Casey Schaufler
2009-11-01 9:23 ` David Wagner
2009-11-01 17:43 ` Casey Schaufler
2009-11-01 20:39 ` David Wagner
2009-11-01 22:05 ` Casey Schaufler
2009-10-26 18:02 ` J. Bruce Fields
2009-10-26 17:57 ` Serge E. Hallyn
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20091025093604.GA1501@ucw.cz \
--to=pavel@ucw.cz \
--cc=bfields@fieldses.org \
--cc=jack@suse.cz \
--cc=jamie@shareable.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=serue@us.ibm.com \
--cc=trond.myklebust@fys.uio.no \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.