linux-kernel - Re: [PATCH] kernel/capability.c get_task

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Date:	Sun, 11 Nov 2007 12:11:07 -0500
From:	Erez Zadok <ezk@...sunysb.edu>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Erez Zadok <ezk@...sunysb.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Ulrich Drepper <drepper@...hat.com>,
	Roland McGrath <roland@...hat.com>,
	"Andrew G. Morgan" <morgan@...nel.org>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Chris Wright <chrisw@...s-sol.org>,
	James Morris <jmorris@...ei.org>,
	Serge Hallyn <serue@...ibm.com>,
	Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH] kernel/capability.c get_task_comm compile error (MMOTM) 

In message <20071111141510.GA29126@...e.hu>, Ingo Molnar writes:
> 
> * Erez Zadok <ezk@...sunysb.edu> wrote:
> 
> > Small patch below fixes compile error.
> 
> > +			char name[sizeof(current->comm)];
> >  			warned++;
> >  			printk(KERN_INFO
> >  			       "warning: process `%s' sets w/ old libcap\n",
> > -			       get_task_comm(current));
> > +			       get_task_comm(name, current));
> 
> that's buggy - get_task_comm() returns void.
> 
> the proper fix would be to first do a get_task_comm() then pass in 
> 'name' as an argument to printk.
> 
> 	Ingo

Ingo, I don't see how it can return NULL.  This is what get_task_comm looks
like in MMOTM-2007-11-10-19-05:

char *get_task_comm(char *buf, struct task_struct *tsk)
{
	/* buf must be at least sizeof(tsk->comm) in size */
	task_lock(tsk);
	strncpy(buf, tsk->comm, sizeof(tsk->comm));
	task_unlock(tsk);
	return buf;
}

The only way it'd return NULL is if a null buf was passed, in which case the
strncpy will oops first.

Erez.
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