linux-kernel - Re: [PATCH] integrity: get comm using lock to avoid race in string printing

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Date:	Wed, 2 Apr 2014 14:45:17 -0400
From:	Richard Guy Briggs <rgb@...hat.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, eparis@...hat.com,
	sgrubb@...hat.com
Subject: Re: [PATCH] integrity: get comm using lock to avoid race in string
 printing

On 14/04/02, Mimi Zohar wrote:
> On Wed, 2014-04-02 at 12:19 -0400, Richard Guy Briggs wrote: 
> > When task->comm is passed directly to audit_log_untrustedstring() without
> > getting a copy or using the task_lock, there is a race that could happen that
> > would output a NULL (\0) in the output string that would effectively truncate
> > the rest of the report text after the comm= field in the audit, losing fields.
> > 
> > Use get_task_comm() to get a copy while acquiring the task_lock to prevent
> > this and to prevent the result from being a mixture of old and new values of
> > comm.
> > 
> > Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> > ---
> >  security/integrity/integrity_audit.c |    3 ++-
> >  1 files changed, 2 insertions(+), 1 deletions(-)
> > 
> > diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
> > index 85253b5..11706a2 100644
> > --- a/security/integrity/integrity_audit.c
> > +++ b/security/integrity/integrity_audit.c
> > @@ -33,6 +33,7 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
> >  			 const char *cause, int result, int audit_info)
> >  {
> >  	struct audit_buffer *ab;
> > +	char comm[sizeof(current->comm)];
> > 
> >  	if (!integrity_audit_info && audit_info == 1)	/* Skip info messages */
> >  		return;
> > @@ -49,7 +50,7 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
> >  	audit_log_format(ab, " cause=");
> >  	audit_log_string(ab, cause);
> >  	audit_log_format(ab, " comm=");
> > -	audit_log_untrustedstring(ab, current->comm);
> > +	audit_log_untrustedstring(ab, get_task_comm(comm, current));
> >  	if (fname) {
> >  		audit_log_format(ab, " name=");
> >  		audit_log_untrustedstring(ab, fname);
> 
> This change is already being upstreamed as commit 73a6b44 "Integrity:
> Pass commname via get_task_comm()".

Excellent.  Missed that.  Thanks.

> thanks,
> 
> Mimi

- RGB

--
Richard Guy Briggs <rbriggs@...hat.com>
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
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