From mboxrd@z Thu Jan 1 00:00:00 1970 From: Prakash Sangappa Subject: Re: [RESEND PATCH] Allow passing tid or pid in SCM_CREDENTIALS without CAP_SYS_ADMIN Date: Fri, 1 Sep 2017 10:30:31 -0700 Message-ID: References: <1503965540-30393-1-git-send-email-prakash.sangappa@oracle.com> <20170829.160232.1901318933754673000.davem@davemloft.net> <87ziahzzhx.fsf@xmission.com> <87inh5ymv2.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: David Miller , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, drepper@redhat.com To: "Eric W. Biederman" Return-path: In-Reply-To: <87inh5ymv2.fsf@xmission.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 8/30/17 10:41 AM, ebiederm@xmission.com wrote: > Prakash Sangappa writes: > > >> With regards to security, the question basically is what is the consequence >> of passing the wrong id. As I understand it, Interpreting the id to be pid >> or tid, the effective uid and gid will be the same. It would be a problem >> only if the incorrect interpretation of the id would refer a different process. >> But that cannot happen as the the global tid(gettid() of a thread is >> unique. > There is also the issue that the receiving process could look, not see > the pid in proc and assume the sending process is dead. That I suspect > is the larger danger. > Will this not be a bug in the application, if it is sending the wrong id? >> As long as the thread is alive, that id cannot reference another process / thread. >> Unless the thread were to exit and the id gets recycled and got used for another >> thread or process. This would be no different from a process exiting and its >> pid getting recycled which is the case now. > Largely I agree. > > If all you want are pid translations I suspect the are far easier ways > thant updating the SCM_CREDENTIALS code. What would be an another easier & efficient way of doing pid translation? Should a new API/mechanism be considered mainly for pid translation purpose for use with pid namespaces, say based on 'pipe' something similar to I_SENDFD? Thanks, -Prakash. > Eric >