linux-kernel - Re: [PATCH 00/15] net: taint when the device driver firmware crashes

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Date:   Sat, 9 May 2020 19:15:23 -0700
From:   Shannon Nelson <snelson@...sando.io>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Luis Chamberlain <mcgrof@...nel.org>, jeyu@...nel.org,
        akpm@...ux-foundation.org, arnd@...db.de, rostedt@...dmis.org,
        mingo@...hat.com, aquini@...hat.com, cai@....pw, dyoung@...hat.com,
        bhe@...hat.com, peterz@...radead.org, tglx@...utronix.de,
        gpiccoli@...onical.com, pmladek@...e.com, tiwai@...e.de,
        schlad@...e.de, andriy.shevchenko@...ux.intel.com,
        keescook@...omium.org, daniel.vetter@...ll.ch, will@...nel.org,
        mchehab+samsung@...nel.org, kvalo@...eaurora.org,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/15] net: taint when the device driver firmware crashes

On 5/9/20 6:58 PM, Andrew Lunn wrote:
> On Sat, May 09, 2020 at 06:01:51PM -0700, Shannon Nelson wrote:
>> On 5/8/20 9:35 PM, Luis Chamberlain wrote:
>>> Device driver firmware can crash, and sometimes, this can leave your
>>> system in a state which makes the device or subsystem completely
>>> useless. Detecting this by inspecting /proc/sys/kernel/tainted instead
>>> of scraping some magical words from the kernel log, which is driver
>>> specific, is much easier. So instead this series provides a helper which
>>> lets drivers annotate this and shows how to use this on networking
>>> drivers.
>>>
>> If the driver is able to detect that the device firmware has come back
>> alive, through user intervention or whatever, should there be a way to
>> "untaint" the kernel?  Or would you expect it to remain tainted?
> Hi Shannon
>
> In general, you don't want to be able to untained. Say a non-GPL
> licenced module is loaded, which taints the kernel. It might then try
> to untaint the kernel to hide its.

Yeah, obviously we don't want this to be abuseable.  I was just 
wondering about reversing this particular status if the broken device 
could get itself fixed.

>
> As for firmware, how much damage can the firmware do as it crashed? If
> it is a DMA master, it could of splattered stuff through
> memory. Restarting the firmware is not going to reverse the damage it
> has done.
>
True, and tho' the driver might get the thing restarted, it wouldn't 
necessarily know what kind of damage had ensued.

Carry on,
sln