From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754410AbaCJUXB (ORCPT ); Mon, 10 Mar 2014 16:23:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56708 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752408AbaCJUW6 (ORCPT ); Mon, 10 Mar 2014 16:22:58 -0400 Date: Mon, 10 Mar 2014 16:21:55 -0400 From: Richard Guy Briggs To: Tetsuo Handa Cc: peterz@infradead.org, paulmck@linux.vnet.ibm.com, laijs@cn.fujitsu.com, akpm@linux-foundation.org, joe@perches.com, keescook@chromium.org, geert@linux-m68k.org, jkosina@suse.cz, viro@zeniv.linux.org.uk, davem@davemloft.net, linux-kernel@vger.kernel.org, mingo@elte.hu, rostedt@goodmis.org, tglx@linutronix.de, linux-security-module@vger.kernel.org Subject: Re: [PATCH] Change task_struct->comm to use RCU. Message-ID: <20140310202155.GR16640@madcap2.tricolour.ca> References: <530BF6B4.3040206@cn.fujitsu.com> <201402252154.HAE13049.QFFSMVOFOOtLJH@I-love.SAKURA.ne.jp> <20140225144643.GU9987@twins.programming.kicks-ass.net> <201403072120.BJB73489.OFMSOFHQFtOJLV@I-love.SAKURA.ne.jp> <20140307155415.GB16640@madcap2.tricolour.ca> <201403082143.BIH86903.QtVMHJFFOOSFOL@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201403082143.BIH86903.QtVMHJFFOOSFOL@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/03/08, Tetsuo Handa wrote: > Richard Guy Briggs wrote: > > > > > Likewise, audit_log_untrustedstring(ab, current->comm) is racy. > > > > > If task->comm was "Hello Linux" until audit_string_contains_control() in > > > > > audit_log_n_untrustedstring() returns false, and becomes "Penguin" before > > > > > memcpy() in audit_log_n_string() is called, memcpy() will emit "Penguin\0nux" > > > > > into the audit log, which results in loss of information (e.g. SELinux > > > > > context) due to the unexpected '\0' byte. > > > > > > > > I expect the audit people don't like this? Also, how do audit and the > > > > LSM crap things interact? I thought they were both different piles of > > > > ignorable goo? > > > > > > I think the audit people do not like loss of information. Some of LSM modules > > > are using audit subsystem for recording security related events. An example is > > > shown later. > > > > This is true, however since comm it untrusted because it can be modified > > by the user audit doesn't trust it anyways, so who cares? > > Excuse me, but did you understand this side effect correctly? > ), you can see that fields after comm= (e.g. exe= subj= key= ) are missing. Ok, from your desciption and example I had clearly not fully understood the problem. > ---------- An audit log with race ---------- > type=SYSCALL msg=audit(1394281498.566:63): arch=40000003 syscall=11 success=yes exit=0 a0=858c9c8 a1=85a6620 a2=858e4a0 a3=85a6620 items=2 ppid=1747 pid=2662 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts1 ses=2 comm="truncated > type=EXECVE msg=audit(1394281498.566:63): argc=1 a0="/tmp/printable-comm" > type=CWD msg=audit(1394281498.566:63): cwd="/root" > type=PATH msg=audit(1394281498.566:63): item=0 name="/tmp/printable-comm" inode=1970955 dev=08:01 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:bin_t:s0 nametype=NORMAL > type=PATH msg=audit(1394281498.566:63): item=1 name=(null) inode=2360187 dev=08:01 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:ld_so_t:s0 nametype=NORMAL > ---------- An audit log with race ---------- > > Even if you don't trust the comm= field, it is annoying for me that fields > after comm= are missing in the audit log. More than annoying, that isn't acceptable. - RGB -- Richard Guy Briggs Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat Remote, Ottawa, Canada Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545