From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752237AbbA0Gqx (ORCPT ); Tue, 27 Jan 2015 01:46:53 -0500 Received: from mail-la0-f51.google.com ([209.85.215.51]:52662 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbbA0Gqu (ORCPT ); Tue, 27 Jan 2015 01:46:50 -0500 Date: Tue, 27 Jan 2015 09:46:47 +0300 From: Cyrill Gorcunov To: Andrew Morton Cc: "Kirill A. Shutemov" , Calvin Owens , Alexey Dobriyan , Oleg Nesterov , "Eric W. Biederman" , Al Viro , "Kirill A. Shutemov" , Peter Feiner , Grant Likely , Siddhesh Poyarekar , linux-kernel@vger.kernel.org, kernel-team@fb.com, Pavel Emelyanov , linux-api@vger.kernel.org, Kees Cook Subject: Re: [RFC][PATCH v2] procfs: Always expose /proc//map_files/ and make it readable Message-ID: <20150127064647.GH651@moon> References: <1421194829-28696-1-git-send-email-calvinowens@fb.com> <20150114152501.GB9820@node.dhcp.inet.fi> <20150114153323.GF2253@moon> <20150114204653.GA26698@mail.thefacebook.com> <20150114211613.GH2253@moon> <20150122024554.GB23762@mail.thefacebook.com> <20150124031544.GA1992748@mail.thefacebook.com> <20150126124731.GA26916@node.dhcp.inet.fi> <20150126210054.GG651@moon> <20150126154346.c63c512e5821e9e0ea31f759@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150126154346.c63c512e5821e9e0ea31f759@linux-foundation.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 26, 2015 at 03:43:46PM -0800, Andrew Morton wrote: > > > > Looks good to me, thanks! Though I would really appreciate if someone > > from security camp take a look as well. > > hm, who's that. Kees comes to mind. yup, I managed to forget CC him. > > And reviewers' task would be a heck of a lot easier if they knew what > /proc/pid/map_files actually does. This: > > akpm3:/usr/src/25> grep -r map_files Documentation > akpm3:/usr/src/25> > > does not help. Sigh. Imagine, for some reason I though we've the docs for that entry, probably i though that way because of many fdinfo snippets i've putted into /proc docs. my bad, sorry. I'll try to prepare docs today. > The 640708a2cff7f81 changelog says: > > : This one behaves similarly to the /proc//fd/ one - it contains > : symlinks one for each mapping with file, the name of a symlink is > : "vma->vm_start-vma->vm_end", the target is the file. Opening a symlink > : results in a file that point exactly to the same inode as them vma's one. > : > : For example the ls -l of some arbitrary /proc//map_files/ > : > : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80403000-7f8f80404000 -> /lib64/libc-2.5.so > : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f8061e000-7f8f80620000 -> /lib64/libselinux.so.1 > : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80826000-7f8f80827000 -> /lib64/libacl.so.1.1.0 > : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80a2f000-7f8f80a30000 -> /lib64/librt-2.5.so > : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80a30000-7f8f80a4c000 -> /lib64/ld-2.5.so > > afacit this info is also available in /proc/pid/maps, so things > shouldn't get worse if the /proc/pid/map_files permissions are at least > as restrictive as the /proc/pid/maps permissions. Is that the case? > (Please add to changelog). > > There's one other problem here: we're assuming that the map_files > implementation doesn't have bugs. If it does have bugs then relaxing > permissions like this will create new vulnerabilities. And the > map_files implementation is surprisingly complex. Is it bug-free? I didn't find any bugs in map-files (and we use it for long time already) so I think it is safe.