linux-kernel - Re: Thoughts on credential switching

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Message-ID: <533446A7.6020003@redhat.com>
Date:	Thu, 27 Mar 2014 16:41:27 +0100
From:	Florian Weimer <fweimer@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Serge Hallyn <serge.hallyn@...ntu.com>
CC:	Jim Lieb <jlieb@...asas.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LSM List <linux-security-module@...r.kernel.org>,
	"Serge E. Hallyn" <serge@...onical.com>,
	Kees Cook <keescook@...omium.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	bfields@...hat.com, Jeff Layton <jlayton@...hat.com>
Subject: Re: Thoughts on credential switching

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?

-- 
Florian Weimer / Red Hat Product Security Team
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