From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out02.mta.xmission.com ([166.70.13.232]:56189 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750888AbdAXXcy (ORCPT ); Tue, 24 Jan 2017 18:32:54 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Seth Forshee Cc: Trond Myklebust , "bfields\@fieldses.org" , "anna.schumaker\@netapp.com" , "linux-nfs\@vger.kernel.org" References: <1481821992-77583-1-git-send-email-seth.forshee@canonical.com> <1481842899.11785.1.camel@primarydata.com> <20161216130609.GA124240@ubuntu-hedt> <20170110145504.GH52661@ubuntu-hedt> <87ziiyfntm.fsf@xmission.com> <20170124151745.GA114560@ubuntu-hedt> <87efzsdq5b.fsf@xmission.com> Date: Wed, 25 Jan 2017 12:28:36 +1300 In-Reply-To: <87efzsdq5b.fsf@xmission.com> (Eric W. Biederman's message of "Wed, 25 Jan 2017 11:55:28 +1300") Message-ID: <87inp4rqaj.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [PATCH] sunrpc: Use current_real_cred() when looking up rpc credentials Sender: linux-nfs-owner@vger.kernel.org List-ID: With respect to nfs and automounts. Does NFS have different automount behavior based on the user performing the automount? If NFS does not have different automount behavior depending on the user we just use the creds of the original mounter of NFS? If NFS does have different automount behavior depending on the user (ouch!) we need to go through the call path and see where it makes sense to over ride things and where it does not. Seth the fundamental problem with your patch was that you were patching a location that is used for more just mounts. I am strongly wishing that we could just change follow_automount from: old_cred = override_creds(&init_cred); mnt = path->dentry->d_op->d_automount(path); revert_creds(old_cred); to: old_cred = override_creds(path->mnt->mnt_sb->s_cred); mnt = path->dentry->d_op->d_automount(path); revert_creds(old_cred); And all will be well with nfs. That does remain possible. But looking at the code path you touched it seems to lookup the cred based purely on the local uid, gid, and groups. Which suggests to me that even the original mounters creds may not be enough :( At which point I am not certain of the solution. But I fear that like autofs NFS actually cares which user is transition the magic mountpoint, and may return different data depending on who transitions the mountpoint first. Ick! Nasty Nasty Ick! Eric