Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755782AbcDKP6M (ORCPT ); Mon, 11 Apr 2016 11:58:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45702 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755644AbcDKP6J (ORCPT ); Mon, 11 Apr 2016 11:58:09 -0400 Message-ID: <1460390286.3268.36.camel@redhat.com> Subject: Re: [PATCH] audit: Don't spam logs with SECCOMP_KILL/RET_ERRNO by default From: Eric Paris To: Paul Moore , Andi Kleen Cc: linux-kernel@vger.kernel.org, Andi Kleen , linux-audit@redhat.com Date: Mon, 11 Apr 2016 10:58:06 -0500 In-Reply-To: References: <1460348008-27076-1-git-send-email-andi@firstfloor.org> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7133 Lines: 186 Just an FYI originally the idea was to follow the pattern of logging set by core dumps see kernel/auditsc.c::audit_core_dumps(). Which is gated by audit_enable but not anything else. I believe at that time the only option was kill, which meant, much like the core dumper, spam was not a likely result given the initiator is killed. I'm all for a way to shut up unsolicited audit messages, especially seccomp with errno or trap. I think it would be best to default 'KILL' to on and everything else to off. I'm no so sure a sysctl is the right way though. Enabling more forms of 'seccomp audit' should really be a part of the audit policy. (p.s. I think the action should be part of the seccomp message, as right now all we know is that Andi's message isn't KILL since the sig=0) -Eric On Mon, 2016-04-11 at 09:30 -0400, Paul Moore wrote: > On Mon, Apr 11, 2016 at 12:13 AM, Andi Kleen > wrote: > > > > From: Andi Kleen > > > > When I run chrome on my opensuse system every time I open > > a new tab the system log is spammed with: > > > > audit[16857]: SECCOMP auid=1000 uid=1000 gid=100 ses=1 pid=16857 > > comm="chrome" exe="/opt/google/chrome/chrome" sig=0 arch=c000003e > > syscall=273 compat=0 ip=0x7fe27c11a444 code=0x50000 > > > > This happens because chrome uses SECCOMP for its sandbox, > > and for some reason always reaches a SECCOMP_KILL or more likely > > SECCOMP_RET_ERRNO in the rule set. > > > > The seccomp auditing was originally added by Eric with > > > >     commit 85e7bac33b8d5edafc4e219c7dfdb3d48e0b4e31 > >     Author: Eric Paris > >     Date:   Tue Jan 3 14:23:05 2012 -0500 > > > >         seccomp: audit abnormal end to a process due to seccomp > > > >         The audit system likes to collect information about > > processes that end > >         abnormally (SIGSEGV) as this may me useful intrusion > > detection information. > >         This patch adds audit support to collect information when > > seccomp > >         forces a task to exit because of misbehavior in a similar > > way. > > > > I don't have any other syscall auditing enabled, > > just the standard user space auditing used by the systemd > > and PAM userland. So basic auditing is alwas enabled, > > but no other kernel auditing. > > > > Add a sysctl to enable this unconditional behavior with default > > to off. This replaces an earlier patch that simply checked > > whether syscall auditing was on, but Paul Moore preferred > > this more elaborate approach. > > > > Signed-off-by: Andi Kleen > > --- > >  Documentation/sysctl/kernel.txt |  9 +++++++++ > >  include/linux/audit.h           |  4 +++- > >  kernel/seccomp.c                |  4 ++++ > >  kernel/sysctl.c                 | 11 +++++++++++ > >  4 files changed, 27 insertions(+), 1 deletion(-) > Quick response as I'm traveling the next few days and > time/connectivity will be spotty ... thanks for sending an updated > patch, some initial thoughts: > > * My thinking was that the sysctl knob could be a threshold value > such > that setting it to 0x00030000 would only log TRAP and KILL. > * With the sysctl tunable defaulting to no-logging there is no need > to > check for audit_enabled, further, checking for audit_enabled would > prevent logging to dmesg/syslog which I believe is valuable (you may > not). > * A bit nitpicky, but considering the possibility of logging to > dmesg/syslog when auditing is disabled, I think > "seccomp-log-threshold" or similar would be a better sysctl name. > > > > > diff --git a/Documentation/sysctl/kernel.txt > > b/Documentation/sysctl/kernel.txt > > index 57653a4..abc6ef9 100644 > > --- a/Documentation/sysctl/kernel.txt > > +++ b/Documentation/sysctl/kernel.txt > > @@ -21,6 +21,7 @@ show up in /proc/sys/kernel: > >  - acct > >  - acpi_video_flags > >  - auto_msgmni > > +- audit_log_seccomp > >  - bootloader_type           [ X86 only ] > >  - bootloader_version        [ X86 only ] > >  - callhome                  [ S390 only ] > > @@ -129,6 +130,14 @@ upon memory add/remove or upon ipc namespace > > creation/removal. > >  Echoing "1" into this file enabled msgmni automatic recomputing. > >  Echoing "0" turned it off. auto_msgmni default value was 1. > > > > +============================================================== > > + > > +audit_log_seccomp > > + > > +When this variable is set to 1 every > > SECCOMP_KILL/SECCOMP_RET_ERRNO > > +results in an audit log. This is generally a bad idea because > > +it leads to a audit message every time Chrome opens a new tab. > > +Defaults to 0. > > > >  ============================================================== > > > > diff --git a/include/linux/audit.h b/include/linux/audit.h > > index e38e3fc..c7787ba 100644 > > --- a/include/linux/audit.h > > +++ b/include/linux/audit.h > > @@ -315,9 +315,11 @@ static inline void audit_inode_child(struct > > inode *parent, > >  } > >  void audit_core_dumps(long signr); > > > > +extern int audit_log_seccomp; > > + > >  static inline void audit_seccomp(unsigned long syscall, long > > signr, int code) > >  { > > -       if (!audit_enabled) > > +       if (!audit_enabled || !audit_log_seccomp) > >                 return; > > > >         /* Force a record to be reported if a signal was delivered. > > */ > > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > > index e1e5a35..09a8b03 100644 > > --- a/kernel/seccomp.c > > +++ b/kernel/seccomp.c > > @@ -25,6 +25,10 @@ > >  #include > >  #endif > > > > +#ifdef CONFIG_AUDIT > > +int audit_log_seccomp __read_mostly = 0; > > +#endif > > + > >  #ifdef CONFIG_SECCOMP_FILTER > >  #include > >  #include > > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > > index 725587f..0c7611e 100644 > > --- a/kernel/sysctl.c > > +++ b/kernel/sysctl.c > > @@ -65,6 +65,7 @@ > >  #include > >  #include > >  #include > > +#include > > > >  #include > >  #include > > @@ -529,6 +530,16 @@ static struct ctl_table kern_table[] = { > >                 .proc_handler   = proc_dointvec, > >         }, > >  #endif > > +#ifdef CONFIG_AUDIT > > +       { > > +               .procname       = "audit-log-seccomp", > > +               .data           = &audit_log_seccomp, > > +               .maxlen         = sizeof(int), > > +               .mode           = 0644, > > +               .proc_handler   = proc_dointvec, > > +       }, > > + > > +#endif > >         { > >                 .procname       = "print-fatal-signals", > >                 .data           = &print_fatal_signals, > > -- > > 2.7.4 > > > >