linux-kernel - Re: [PATCH RFC] watchdog: core: don't try to stop device if not running

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Mon, 8 Apr 2013 10:43:52 +0200
From:	Hector Palacios <hector.palacios@...i.com>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"wim@...ana.be" <wim@...ana.be>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] watchdog: core: don't try to stop device if not running

On 04/08/2013 10:16 AM, Guenter Roeck wrote:
> On Mon, Apr 08, 2013 at 09:48:57AM +0200, Hector Palacios wrote:
>> On 04/05/2013 08:34 PM, Guenter Roeck wrote:
>>> On Fri, Apr 05, 2013 at 06:09:44PM +0200, Hector Palacios wrote:
>>>> A watchdog device may be stopped from userspace using WDIOC_SETOPTIONS
>>>> ioctl and flag WDIOS_DISABLECARD. If the device is closed after this
>>>> operation, watchdog_release() is called and status bits checked for
>>>> stopping it. Besides, if the device has not been unregistered a critical
>>>> message "watchdog did not stop!" is printed, although the ioctl may have
>>>> successfully stopped it already.
>>>>
>>>> Without the patch a user application sample code like this will successfully
>>>> stop the watchdog, but the kernel will output the message
>>>> "watchdog did not stop!":
>>>>
>>>> 	wd_fd = open("/dev/watchdog", O_RDWR);
>>>>
>>>> 	flags = WDIOS_DISABLECARD;
>>>> 	ioctl(wd_fd, WDIOC_SETOPTIONS, &flags);
>>>>
>>>> 	close(wd_fd);
>>>>
>>>> Signed-off-by: Hector Palacios <hector.palacios@...i.com>
>>>
>>> How about the following patch instead ?
>>>
>>> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
>>> index 08b48bb..9775e8d 100644
>>> --- a/drivers/watchdog/watchdog_dev.c
>>> +++ b/drivers/watchdog/watchdog_dev.c
>>> @@ -469,7 +469,9 @@ static int watchdog_release(struct inode *inode, struct file *file)
>>>   	 * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
>>>   	 * watchdog_stop will fail.
>>>   	 */
>>> -	if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
>>> +	if (!test_bit(WDOG_ACTIVE, &wdd->status))
>>> +		err = 0;
>>> +	else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
>>>   	    !(wdd->info->options & WDIOF_MAGICCLOSE))
>>>   		err = watchdog_stop(wdd);
>>>
>>> Much less invasive and the result is the same.
>>
>> I like the simplicity but it is kind of inverted logic to initially
>> define err = -EBUSY only to turn it to zero later, so I'm rebuilding
>> your approach like this:
>>
>> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
>> index ef8edec..a4163cd 100644
>> --- a/drivers/watchdog/watchdog_dev.c
>> +++ b/drivers/watchdog/watchdog_dev.c
>> @@ -463,16 +463,19 @@ out:
>>   static int watchdog_release(struct inode *inode, struct file *file)
>>   {
>>          struct watchdog_device *wdd = file->private_data;
>> -       int err = -EBUSY;
>> +       int err = 0;
>>
>>          /*
>>           * We only stop the watchdog if we received the magic character
>>           * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
>>           * watchdog_stop will fail.
>>           */
>> -       if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
>> -           !(wdd->info->options & WDIOF_MAGICCLOSE))
>> +       if (test_bit(WDOG_ACTIVE, &wdd->status))
>> +               err = -EBUSY;
>> +       else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
>> +           !(wdd->info->options & WDIOF_MAGICCLOSE)) {
>>                  err = watchdog_stop(wdd);
>> +       }
>
> Ok, but the added { } are unnecessary and violate coding style rules.

Oops. Remainders of a debug message. Thanks for pointing out.

-- 
Héctor Palacios
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/