linux-kernel - Re: AT91SAM9/CAP9 watchdog driver

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Date:	Mon, 2 Jun 2008 07:58:08 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Andrew Victor" <avictor.za@...il.com>
Cc:	akpm@...ux-foundation.org, wim@...ana.be,
	LAK <linux-arm-kernel@...ts.arm.linux.org.uk>,
	"Linux Kernel list" <linux-kernel@...r.kernel.org>
Subject: Re: AT91SAM9/CAP9 watchdog driver


> +static long at91_wdt_ioctl(struct file *file, unsigned int cmd,
> +		unsigned long arg)
> +{
> +	void __user *argp = (void __user *)arg;
> +	int __user *p = argp;

No locking.. so you could get two set timeout calls in parallel. Probably
you need a simple mutex in at91_wdt_settimeout();


> +	res = misc_register(&at91wdt_miscdev);
> +	if (res)
> +		return res;
> +
> +	/* Set watchdog */
> +	if (at91_wdt_settimeout(wdt_timeout) == -EINVAL) {
> +		pr_info("at91sam9_wdt: timeout must be between 1 and %d.\n",
> +			WDT_MAX_TIME);
> +		return 0;

At the moment those two are safe. When the open lock_kernel
goes away it will be possible to get

			misc_register
						open
						ioctl
			wdt_settimout()

So you may want to swap those two around (and disable the timer if the
register fails ?), or lock the open against the register routine.

Otherwise looks good.

Alan
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