From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755190Ab2BCXO5 (ORCPT ); Fri, 3 Feb 2012 18:14:57 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:34524 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754538Ab2BCXOz convert rfc822-to-8bit (ORCPT ); Fri, 3 Feb 2012 18:14:55 -0500 MIME-Version: 1.0 In-Reply-To: <20120202153232.GB4583@sergelap> References: <1327788715-24076-1-git-send-email-wad@chromium.org> <1327788715-24076-2-git-send-email-wad@chromium.org> <20120202153232.GB4583@sergelap> Date: Fri, 3 Feb 2012 15:14:52 -0800 Message-ID: Subject: Re: [PATCH v6 2/3] seccomp_filters: system call filtering using BPF From: Will Drewry To: "Serge E. Hallyn" Cc: linux-kernel@vger.kernel.org, keescook@chromium.org, john.johansen@canonical.com, coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com, djm@mindrot.org, torvalds@linux-foundation.org, segoon@openwall.com, rostedt@goodmis.org, jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com, penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, luto@mit.edu, mingo@elte.hu, akpm@linux-foundation.org, khilman@ti.com, borislav.petkov@amd.com, amwang@redhat.com, oleg@redhat.com, ak@linux.intel.com, eric.dumazet@gmail.com, gregkh@suse.de, dhowells@redhat.com, daniel.lezcano@free.fr, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, olofj@chromium.org, mhalcrow@google.com, dlaor@redhat.com, corbet@lwn.net, alan@lxorguk.ukuu.org.uk, indan@nul.nu, mcgrathr@chromium.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 2, 2012 at 7:32 AM, Serge E. Hallyn wrote: > Quoting Will Drewry (wad@chromium.org): >> [This patch depends on luto@mit.edu's no_new_privs patch: >>  https://lkml.org/lkml/2012/1/12/446 >> ] >> >> This patch adds support for seccomp mode 2.  This mode enables dynamic >> enforcement of system call filtering policy in the kernel as specified >> by a userland task.  The policy is expressed in terms of a Berkeley >> Packet Filter program, as is used for userland-exposed socket filtering. >> Instead of network data, the BPF program is evaluated over struct >> seccomp_filter_data at the time of the system call. >> >> A filter program may be installed by a userland task by calling >>   prctl(PR_ATTACH_SECCOMP_FILTER, &fprog); >> where fprog is of type struct sock_fprog. >> >> If the first filter program allows subsequent prctl(2) calls, then >> additional filter programs may be attached.  All attached programs >> must be evaluated before a system call will be allowed to proceed. >> >> To avoid CONFIG_COMPAT related landmines, once a filter program is >> installed using specific is_compat_task() value, it is not allowed to >> make system calls using the alternate entry point. >> >> Filter programs will be inherited across fork/clone and execve, however >> the installation of filters must be preceded by setting 'no_new_privs' >> to ensure that unprivileged tasks cannot attach filters that affect >> privileged tasks (e.g., setuid binary).  Tasks with CAP_SYS_ADMIN >> in their namespace may install inheritable filters without setting >> the no_new_privs bit. >> >> There are a number of benefits to this approach. A few of which are >> as follows: >> - BPF has been exposed to userland for a long time. >> - Userland already knows its ABI: system call numbers and desired >>   arguments >> - No time-of-check-time-of-use vulnerable data accesses are possible. >> - system call arguments are loaded on demand only to minimize copying >>   required for system call number-only policy decisions. >> >> This patch includes its own BPF evaluator, but relies on the >> net/core/filter.c BPF checking code.  It is possible to share >> evaluators, but the performance sensitive nature of the network >> filtering path makes it an iterative optimization which (I think :) can >> be tackled separately via separate patchsets. (And at some point sharing >> BPF JIT code!) >> >>  v6: - fix memory leak on attach compat check failure >>      - require no_new_privs || CAP_SYS_ADMIN prior to filter >>        installation. (luto@mit.edu) >>      - s/seccomp_struct_/seccomp_/ for macros/functions >>        (amwang@redhat.com) >>      - cleaned up Kconfig (amwang@redhat.com) >>      - on block, note if the call was compat (so the # means something) >>  v5: - uses syscall_get_arguments >>        (indan@nul.nu,oleg@redhat.com, mcgrathr@chromium.org) >>      - uses union-based arg storage with hi/lo struct to >>        handle endianness.  Compromises between the two alternate >>        proposals to minimize extra arg shuffling and account for >>        endianness assuming userspace uses offsetof(). >>        (mcgrathr@chromium.org, indan@nul.nu) >>      - update Kconfig description >>      - add include/seccomp_filter.h and add its installation >>      - (naive) on-demand syscall argument loading >>      - drop seccomp_t (eparis@redhat.com) >>  v4: - adjusted prctl to make room for PR_[SG]ET_NO_NEW_PRIVS >>      - now uses current->no_new_privs >>          (luto@mit.edu,torvalds@linux-foundation.com) >>      - assign names to seccomp modes (rdunlap@xenotime.net) >>      - fix style issues (rdunlap@xenotime.net) >>      - reworded Kconfig entry (rdunlap@xenotime.net) >>  v3: - macros to inline (oleg@redhat.com) >>      - init_task behavior fixed (oleg@redhat.com) >>      - drop creator entry and extra NULL check (oleg@redhat.com) >>      - alloc returns -EINVAL on bad sizing (serge.hallyn@canonical.com) >>      - adds tentative use of "always_unprivileged" as per >>        torvalds@linux-foundation.org and luto@mit.edu >>  v2: - (patch 2 only) >> >> Signed-off-by: Will Drewry > > Hi Will, > > as far as I can tell based on changelog I suspect you could have > kept my Acked-by (from v3?).  However, I'll wait until your next > submission (as I see there were a few change requests), and do a > final complete new review of that. Thanks, Serge! I just failed at the proper protocol and didn't mean to not include your Acked-by. However, I am changing a fair amount of the internals this time around, so I'll be happy to have another full review. > Thanks for continuing to push on this. Definitely! I've been traveling this week, so it's been a bit slow going, but I hope to have the next rev up early next week if not sooner. Cheers! will