From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755239AbaC0Pll (ORCPT ); Thu, 27 Mar 2014 11:41:41 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47752 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753873AbaC0Plj (ORCPT ); Thu, 27 Mar 2014 11:41:39 -0400 Message-ID: <533446A7.6020003@redhat.com> Date: Thu, 27 Mar 2014 16:41:27 +0100 From: Florian Weimer User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Andy Lutomirski , Serge Hallyn CC: Jim Lieb , "Eric W. Biederman" , LSM List , "Serge E. Hallyn" , Kees Cook , Linux FS Devel , "Theodore Ts'o" , "linux-kernel@vger.kernel.org" , bfields@redhat.com, Jeff Layton Subject: Re: Thoughts on credential switching References: <20140327004225.GA20247@sergelap> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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