linux-kernel - Re: [PATCH 2/2] watchdog: dw_wdt: keepalive the watchdog at write time

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

Date:	Fri, 8 May 2015 10:41:33 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Doug Anderson <dianders@...omium.org>,
	"wim@...ana.be" <wim@...ana.be>,
	"linux@...ck-us.net" <linux@...ck-us.net>
CC:	"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] watchdog: dw_wdt: keepalive the watchdog at write
 time

On Thu, 7 May 2015 15:09:24 -0700
Doug Anderson <dianders@...omium.org> wrote:

> If you've got code that does this in a tight loop
>   1. Open watchdog
>   2. Send 'expect close'
>   3. Close watchdog
> ...you'll eventually trigger a watchdog reset.  You can reproduce this
> by using daisydog (1) and running:
>   while true; do daisydog -c > /dev/null; done
> 
> The problem is that each time you write to the watchdog for 'expect
> close' it moves the timer .5 seconds out.  The timer thus never fires
> and never pats the watchdog for you.
> 
> 1: http://git.chromium.org/gitweb/?p=chromiumos/third_party/daisydog.git
> 
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
>  drivers/watchdog/dw_wdt.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
> index 3fa2f19..ff5d734 100644
> --- a/drivers/watchdog/dw_wdt.c
> +++ b/drivers/watchdog/dw_wdt.c
> @@ -220,6 +220,7 @@ static ssize_t dw_wdt_write(struct file *filp, const char __user *buf,
>  	}
>  
>  	dw_wdt_set_next_heartbeat();
> +	dw_wdt_keepalive();
>  	mod_timer(&dw_wdt.timer, jiffies + WDT_TIMEOUT);
>  
>  	return len;

Tested-by: Jisheng Zhang <jszhang@...vell.com>
--
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/