linux-kernel - Re: [PATCH 1/2] driver/aspeed-wdt: fix pretimeout for counting down logic

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]

Message-ID: <4602bffc-55b0-4a0a-9c36-ac391904d974@roeck-us.net>
Date: Tue, 18 Feb 2025 17:40:23 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Andrew Jeffery <andrew@...econstruct.com.au>,
 Heyi Guo <guoheyi@...ux.alibaba.com>, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, linux-watchdog@...r.kernel.org
Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>, Joel Stanley <joel@....id.au>,
 Eddie James <eajames@...ux.ibm.com>
Subject: Re: [PATCH 1/2] driver/aspeed-wdt: fix pretimeout for counting down
 logic

On 2/18/25 17:25, Andrew Jeffery wrote:
> On Mon, 2025-02-17 at 21:33 -0800, Guenter Roeck wrote:
>> On 2/17/25 19:16, Heyi Guo wrote:
>>> Aspeed watchdog uses counting down logic, so the value set to register
>>> should be the value of subtracting pretimeout from total timeout.
>>>
>>> Fixes: 9ec0b7e06835 ("watchdog: aspeed: Enable pre-timeout interrupt")
>>>
>>> Signed-off-by: Heyi Guo <guoheyi@...ux.alibaba.com>
>>>
>>> Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>
>>> Cc: Guenter Roeck <linux@...ck-us.net>
>>> Cc: Joel Stanley <joel@....id.au>
>>> Cc: Andrew Jeffery <andrew@...econstruct.com.au>
>>> Cc: Eddie James <eajames@...ux.ibm.com>
>>> ---
>>>    drivers/watchdog/aspeed_wdt.c | 7 +++++++
>>>    1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/watchdog/aspeed_wdt.c b/drivers/watchdog/aspeed_wdt.c
>>> index b4773a6aaf8c..520d8aba12a5 100644
>>> --- a/drivers/watchdog/aspeed_wdt.c
>>> +++ b/drivers/watchdog/aspeed_wdt.c
>>> @@ -187,6 +187,13 @@ static int aspeed_wdt_set_pretimeout(struct watchdog_device *wdd,
>>>          u32 actual = pretimeout * WDT_RATE_1MHZ;
>>>          u32 s = wdt->cfg->irq_shift;
>>>          u32 m = wdt->cfg->irq_mask;
>>> +       u32 reload = readl(wdt->base + WDT_RELOAD_VALUE);
>>> +
>>
>> It is unusual to use a register value here and not the configured timeout
>> value. I would have assumed that pretimeout is compared against wdt->timout,
>> not against the register value, and that the multiplication with WDT_RATE_1MHZ
>> is done after validation. This needs an explanation.
> 
> +1
> 
>>
>>> +       if (actual >= reload)
>>> +               return -EINVAL;
>>> +
>>
>> On top of that, you'll also need to explain why watchdog_pretimeout_invalid()
>> and with it the validation in watchdog_set_pretimeout() does not work for this
>> watchdog and why this extra validation is necessary.
> 
> +1 as well.
> 
> Further, the logic looks broken regardless for the AST2400 where
> there's no pretimeout support. aspeed_wdt_set_pretimeout() should error
> out if wdt->cfg->irq_mask is 0.
> 

It should not register as supporting pretimeout in the first place.

Guenter