From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 22 Feb 2017 09:17:58 -0600 From: Seth Forshee To: David Howells Cc: viro@ZenIV.linux.org.uk, linux-kernel@vger.kernel.org, "Eric W. Biederman" , linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org Subject: Re: [PATCH] vfs: Partially revert addition of cred override in follow_automount() Message-ID: <20170222151758.GB29966@ubuntu-hedt> References: <148777059228.7183.7698026974948697349.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <148777059228.7183.7698026974948697349.stgit@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Wed, Feb 22, 2017 at 01:36:32PM +0000, David Howells wrote: > The following commit: > > commit aeaa4a79ff6a5ed912b7362f206cf8576fca538b > Author: Eric W. Biederman > Date: Sat Jul 23 11:20:44 2016 -0500 > fs: Call d_automount with the filesystems creds > > brackets the call to ->d_automount() with override_creds() and > revert_creds(), setting the initial credentials for use whilst > automounting. > > This, however, breaks AFS as it's no longer able to access the calling > process's keyrings to read the destination on a mountpoint. This has gone > unnoticed till now because, to this point, stat'ing or validating the inode > caused the body of the mountpoint to be read into the pagecache (so that we > could determine whether what we were looking at was really a mountpoint). > > However, the page containing the mountpoint destination is merely *cached* > and not pinned. If it gets discarded and we try to read it in d_automount, > we may fail because we have no authentication tokens available. > > So, for the moment, revert the addition of override_creds() and > revert_creds() and their variable. > > Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") > Signed-off-by: David Howells > cc: Seth Forshee > cc: "Eric W. Biederman" > cc: Al Viro Eric's already applied a patch that should fix this problem. As far as I know it's only been tested against NFS though, so you might want to test that it also fixes the issue with AFS. https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=93faccbbfa958a9668d3ab4e30f38dd205cee8d8 Thanks, Seth