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From: Andy Lutomirski <luto@amacapital.net>
To: Florian Weimer <fweimer@redhat.com>
Cc: Serge Hallyn <serge.hallyn@ubuntu.com>,
	Jim Lieb <jlieb@panasas.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	LSM List <linux-security-module@vger.kernel.org>,
	"Serge E. Hallyn" <serge@canonical.com>,
	Kees Cook <keescook@chromium.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	"Theodore Ts'o" <tytso@mit.edu>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	bfields@redhat.com, Jeff Layton <jlayton@redhat.com>
Subject: Re: Thoughts on credential switching
Date: Thu, 27 Mar 2014 09:21:22 -0700	[thread overview]
Message-ID: <CALCETrXbN1vgTNJB2UGeDvxJ+pwsqO1dOfea5Crs4As1A8dKUg@mail.gmail.com> (raw)
In-Reply-To: <533446A7.6020003@redhat.com>

On Thu, Mar 27, 2014 at 8:41 AM, Florian Weimer <fweimer@redhat.com> wrote:
> On 03/27/2014 02:01 AM, Andy Lutomirski wrote:
>
>> Essentially, it's a performance problem.  knfsd has override_creds,
>> and it can cache struct cred.  But userspace doing the same thing
>> (i.e. impersonating a user) has to do setresuid, setresgid, and
>> setgroups, which kills performance, since it results in something like
>> five RCU callbacks per impersonation round-trip.
>
>
> Do you mean setfsuid instead of setresuid?

No, but I should have given context.  setfsuid sucks, since its return
value is garbage.  It's also pointless nowadays, since setresuid can
be used to sanely change only the effective uid, and doing so should
be secure.

See: http://article.gmane.org/gmane.linux.kernel/1540880

--Andy

  reply	other threads:[~2014-03-27 16:21 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-27  0:23 Thoughts on credential switching Andy Lutomirski
2014-03-27  0:42 ` Serge Hallyn
2014-03-27  1:01   ` Andy Lutomirski
2014-03-27 15:41     ` Florian Weimer
2014-03-27 16:21       ` Andy Lutomirski [this message]
2014-03-27  2:48 ` Jeff Layton
2014-03-27  3:05   ` Andy Lutomirski
2014-03-27  3:25     ` Jeff Layton
2014-03-27 14:08       ` Jeff Layton
2014-03-29  6:43         ` Alex Elsayed
2014-03-30 13:03         ` Theodore Ts'o
2014-03-30 18:56           ` Andy Lutomirski
2014-03-31 11:51           ` Jeff Layton
2014-03-31 18:06             ` Trond Myklebust
2014-03-31 18:06               ` Trond Myklebust
2014-03-31 18:12               ` Jeff Layton
2014-03-31 18:12                 ` Jeff Layton
2014-03-31 19:26               ` Andy Lutomirski
2014-03-31 20:14                 ` Trond Myklebust
2014-03-31 21:25                   ` Andy Lutomirski
2014-03-27 12:46 ` Florian Weimer
2014-03-27 13:02   ` Jeff Layton
2014-03-27 13:06     ` Florian Weimer
2014-03-27 13:33       ` Boaz Harrosh
2014-04-22 11:37         ` Florian Weimer
2014-04-22 12:14           ` Boaz Harrosh
2014-04-22 16:35             ` Jim Lieb
2014-04-22 16:35               ` Jim Lieb
2014-03-27 14:01       ` Jeff Layton
2014-03-27 18:26         ` Jeremy Allison
2014-03-27 18:46           ` Andy Lutomirski
2014-03-27 18:56             ` Jeremy Allison
2014-03-27 19:02               ` Andy Lutomirski
2014-03-27 19:30           ` Jim Lieb
2014-03-27 19:45             ` Andy Lutomirski
2014-03-27 20:47               ` Jim Lieb
2014-03-27 20:47                 ` Jim Lieb
2014-03-27 21:19                 ` Andy Lutomirski
2014-03-31 10:44 ` One Thousand Gnomes
2014-03-31 16:49   ` Andy Lutomirski
2014-04-01 20:22     ` One Thousand Gnomes
2014-03-31 19:05   ` Jeremy Allison

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