From: Willy Tarreau <w@1wt.eu>
To: Kees Cook <keescook@chromium.org>
Cc: Dirk Steinmetz <public@rsjtdrjgfuzkfg.com>,
Michael Kerrisk-manpages <mtk.manpages@gmail.com>,
Serge Hallyn <serge.hallyn@ubuntu.com>,
Seth Forshee <seth.forshee@canonical.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Linux FS Devel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Serge Hallyn <serge.hallyn@canonical.com>,
"security@kernel.org" <security@kernel.org>
Subject: Re: [RFC] namei: prevent sgid-hardlinks for unmapped gids
Date: Wed, 4 Nov 2015 07:58:20 +0100 [thread overview]
Message-ID: <20151104065820.GF21740@1wt.eu> (raw)
In-Reply-To: <CAGXu5jKCCq4hs_nerQYMnC1frA3qKkCxxQTjpS2gw-7dPZAX+w@mail.gmail.com>
On Tue, Nov 03, 2015 at 03:29:55PM -0800, Kees Cook wrote:
> Using "write" does kill the set-gid bit. I haven't looked at
> why.
> Al or anyone else, is there a meaningful distinction here?
I remember this one, I got caught once while trying to put a shell into
a suid-writable file to get some privileges someone forgot to offer me :-)
It's done by should_remove_suid() which is called upon write() and truncate().
> Should the
> mmap MAP_SHARED-write trigger the loss of the set-gid bit too? While
> holding the file open with either open or mmap, I get a Text-in-use
> error, so I would kind of expect the same behavior between either
> close() and munmap(). I wonder if this is a bug, and if so, then your
> link patch is indeed useful again. :)
I don't see how this could be done with mmap(). Maybe we have a way to know
when the first write is performed via this path, I have no idea.
Willy
next prev parent reply other threads:[~2015-11-04 6:58 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-10 14:59 [PATCH] namei: permit linking with CAP_FOWNER in userns Dirk Steinmetz
2015-10-20 14:09 ` Dirk Steinmetz
2015-10-27 14:33 ` Seth Forshee
2015-10-27 18:08 ` Dirk Steinmetz
2015-10-27 20:28 ` Serge Hallyn
2015-10-28 15:07 ` Dirk Steinmetz
2015-10-28 17:33 ` Serge Hallyn
2015-11-02 15:10 ` Dirk Steinmetz
2015-11-02 18:02 ` Serge Hallyn
2015-11-02 19:57 ` Andy Lutomirski
2015-11-03 0:39 ` [RFC] namei: prevent sgid-hardlinks for unmapped gids Dirk Steinmetz
2015-11-03 15:44 ` Serge Hallyn
2015-11-03 18:20 ` Kees Cook
2015-11-03 23:21 ` Dirk Steinmetz
2015-11-03 23:29 ` Kees Cook
2015-11-04 6:58 ` Willy Tarreau [this message]
2015-11-04 17:59 ` Andy Lutomirski
2015-11-04 18:15 ` Willy Tarreau
2015-11-04 18:17 ` Andy Lutomirski
2015-11-04 18:28 ` Willy Tarreau
2015-11-06 21:59 ` Kees Cook
2015-11-06 22:30 ` Andy Lutomirski
2015-11-07 0:11 ` Kees Cook
2015-11-07 0:16 ` Kees Cook
2015-11-07 0:48 ` Andy Lutomirski
2015-11-07 5:05 ` Kees Cook
2015-11-08 2:02 ` Theodore Ts'o
2015-11-10 15:08 ` Jan Kara
2015-11-19 20:11 ` Kees Cook
2015-11-19 21:57 ` Andy Lutomirski
2015-11-19 22:02 ` Dave Chinner
2015-11-20 0:11 ` Kees Cook
2015-11-04 14:46 ` Serge E. Hallyn
2015-10-27 21:04 ` [PATCH] namei: permit linking with CAP_FOWNER in userns Eric W. Biederman
2015-11-03 17:51 ` Kees Cook
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=20151104065820.GF21740@1wt.eu \
--to=w@1wt.eu \
--cc=ebiederm@xmission.com \
--cc=keescook@chromium.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mtk.manpages@gmail.com \
--cc=public@rsjtdrjgfuzkfg.com \
--cc=security@kernel.org \
--cc=serge.hallyn@canonical.com \
--cc=serge.hallyn@ubuntu.com \
--cc=seth.forshee@canonical.com \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).