netdev - Re: [PATCH V7 4/8] posix clocks: hook dynamic clocks into system calls

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Date:	Wed, 22 Dec 2010 09:21:28 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Christoph Lameter <cl@...ux.com>,
	David Miller <davem@...emloft.net>,
	John Stultz <johnstul@...ibm.com>,
	Krzysztof Halasa <khc@...waw.pl>,
	Peter Zijlstra <peterz@...radead.org>,
	Rodolfo Giometti <giometti@...ux.it>
Subject: Re: [PATCH V7 4/8] posix clocks: hook dynamic clocks into system
 calls

On Fri, Dec 17, 2010 at 11:03:46AM +0100, Thomas Gleixner wrote:
> So you could do the following:
...
> static int get_posix_clock(const clockid_t id, struct posix_clock_descr *cd)
> {
> 	struct file *fp = fget(CLOCKID_TO_FD(id));
> 	int ret;
> 
> 	if (!fp || fp->f_op->open != posix_clock_open || !fp->private_data)
> 	   	return -ENODEV;
> 	ret = get_fd_clk(cd, fp);
> 	if (ret)
> 		fput(fp);
> 	return ret;
> }

In order to avoid leaking a fp reference, shouldn't this go like:

static int get_posix_clock(const clockid_t id, struct posix_clock_desc *cd)
{
	struct file *fp = fget(CLOCKID_TO_FD(id));
	int ret = -EINVAL;

	if (!fp)
		return ret;
	if (fp->f_op->open != posix_clock_open || !fp->private_data)
		goto out;
	ret = get_fd_clk(cd, fp);
out:
	if (ret)
		fput(fp);
	return ret;
}

Thanks again for your help,
Richard


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