linux-kernel - Re: Stopping watchdog in watchdog driver remove functions

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:   Sun, 1 Jan 2017 12:14:22 +0100
From:   Wim Van Sebroeck <wim@...ana.be>
To:     Guenter Roeck <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>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Mans Rullgard <mans@...sr.com>,
        Justin Chen <justinpopo6@...il.com>,
        Wenyou Yang <wenyou.yang@...el.com>,
        Naidu Tellapati <naidu.tellapati@...il.com>
Subject: Re: Stopping watchdog in watchdog driver remove functions

Hi Guenter,

> I noticed that several watchdog drivers stop the watchdog in trhe driver 
> remove function.
> A non-exhaustive list of drivers doing that is
> 
> 	drivers/watchdog/bcm7038_wdt.c
> 	drivers/watchdog/cadence_wdt.c
> 	drivers/watchdog/imgpdc_wdt.c
> 	drivers/watchdog/jz4740_wdt.c
> 	drivers/watchdog/kempld_wdt.c
> 	drivers/watchdog/max77620_wdt.c
> 	drivers/watchdog/moxart_wdt.c
> 	drivers/watchdog/sama5d4_wdt.c
> 	drivers/watchdog/tangox_wdt.c
> 	drivers/watchdog/tegra_wdt.c
> 
> Since a watchdog has to be closed for its driver to be removable, one 
> situation
> where a watchdog is still running on unload is where the watchdog was 
> opened but
> not closed properly (eg by killing the watchdog application, or if the 
> 'nowayout'
> flag is set).
> 
> Given that, does it even make sense to stop the watchdog in the remove 
> function ?
> Should it even be permitted ?

>From an API point of view: if WDIOF_MAGICCLOSE is being used then the watchdog
_SHOULD_ continue to run when the watchdog was not properly closed (which
normally also results in a reboot of the system).
if WDIOF_MAGICCLOSE is not being used then closing the watchdog device means
that the driver needs to stop the watchdog.

Kind regards and happy new year to you all,
Wim.