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

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Message-ID: <1396460387.20325.22.camel@dhcp-9-2-203-236.watson.ibm.com>
Date:	Wed, 02 Apr 2014 13:39:47 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Richard Guy Briggs <rgb@...hat.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 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()".

thanks,

Mimi

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