linux-kernel - Re: [PATCH 3/3] tomoyo: robustify handling of mm->exe

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Message-Id: <201502192007.AFI30725.tHFFOOMVFOQSLJ@I-love.SAKURA.ne.jp>
Date:	Thu, 19 Feb 2015 20:07:31 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	dave@...olabs.net
Cc:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, takedakn@...data.co.jp,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 3/3] tomoyo: robustify handling of mm->exe_file

Thank you, but I think this patch is wrong and redundant.

Davidlohr Bueso wrote:
> On Wed, 2015-02-18 at 16:10 -0800, Davidlohr Bueso wrote:
> > +static const char *tomoyo_get_exe(struct mm_struct *mm)
> > +{
> > +	struct file *exe_file;
> > +	const char *cp = NULL;
> > +
> > +	if (!mm)
> > +		return NULL;
> > +	exe_file = get_mm_exe_file(mm);
> > +	if (!exe_file)
> > +		return NULL;
> > +
> > +	cp = tomoyo_realpath_from_path(&exe_file->f_path);
> 
> tomoyo_realpath_from_path can return NULL here, thus we'd leak the
> f_path in the caller... I guess this should be:
> 
> > +	path_get(&exe_file->f_path);
> 
> 	if (cp)
> 		path_get(&exe_file->f_path);
> 
Why do we need to let the caller call path_put() ?
There is no need to do like proc_exe_link() does, for
tomoyo_get_exe() returns pathname as "char *".

> > +	fput(exe_file);
> > +	return cp;
> > +}
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