From: ebiederm@xmission•com (Eric W. Biederman)
To: David Miller <davem@davemloft•net>
Cc: torvalds@linux-foundation•org, netdev@vger•kernel.org, serge@hallyn•com
Subject: Re: net: fix incorrect credentials passing
Date: Sat, 20 Apr 2013 03:53:50 -0700 [thread overview]
Message-ID: <87ip3h4gn5.fsf@xmission.com> (raw)
In-Reply-To: <20130419.215856.1499421731544629706.davem@davemloft.net> (David Miller's message of "Fri, 19 Apr 2013 21:58:56 -0400 (EDT)")
David Miller <davem@davemloft•net> writes:
> From: Linus Torvalds <torvalds@linux-foundation•org>
> Date: Fri, 19 Apr 2013 18:32:32 -0700 (PDT)
>
>> Commit 257b5358b32f ("scm: Capture the full credentials of the scm
>> sender") changed the credentials passing code to pass in the effective
>> uid/gid instead of the real uid/gid.
>
> Yep, that's exactly what happened, via a very twisty and winding road.
>
> The helper cred_to_ucred(), which was created by commit
> 3f551f9436c05a3b5eccdd6e94733df5bb98d2a5 ("sock: Introduce
> cred_to_ucred") seemed to be aimed at providing the semantics expected
> by SO_PEERCRED, which does in fact want to use the effective UIDs and
> GIDs.
>
> The SO_PEERCRED side of this can be seen more clearly in commit
> 109f6e39fa07c48f580125f531f46cb7c245b528 ("af_unix: Allow SO_PEERCRED
> to work across namespaces.")
>
> The error begins when we try to use that helper in the SCM credentials
> code.
>
> Initially, cred_to_ucred() is what was used by scm_set_cred(). Then
> it got changed in dbe9a4173ea53b72b2c35d19f676a85b69f1c9fe ("scm:
> Don't use struct ucred in NETLINK_CB and struct scm_cookie.") which
> continues the error by propagating the effective UID/GID usage from
> cred_to_ucred() into explicit accesses inside of scm_set_cred().
>
> So, as stated, the error originates from trying to use this common
> helper for both SO_PEERCERD and the SCM stuff, the latter of which
> does not want to use effective UIDs and GIDs.
>
>> This just undoes that (presumably unintentional) part of the commit.
>
> Indeed, I'd say this was an oversight in semantic differences when
> creating the cred_to_ucred() helper.
>
> Eric B. please review and ACK this.
I have followed this only briefly and looked at this only quickly but I
David I read the git history the same way you do. I introduced a
behavior change when the cred_to_ucred helper was introduced into
scm_set_cred(). Linus's patch restores the original behavior.
So.
Acked-by: "Eric W. Biederman" <ebiederm@xmission•com>
Hopefully that is sufficient. I am in the midst of taking care of some
non-software things this week and I really don't have the time to look
more closely.
Eric
next prev parent reply other threads:[~2013-04-20 10:54 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-20 1:32 net: fix incorrect credentials passing Linus Torvalds
2013-04-20 1:58 ` David Miller
2013-04-20 10:53 ` Eric W. Biederman [this message]
2013-04-20 20:58 ` David Miller
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=87ip3h4gn5.fsf@xmission.com \
--to=ebiederm@xmission$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=netdev@vger$(echo .)kernel.org \
--cc=serge@hallyn$(echo .)com \
--cc=torvalds@linux-foundation$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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