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

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Message-ID: <20200510015814.GE362499@lunn.ch>
Date:   Sun, 10 May 2020 03:58:14 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Shannon Nelson <snelson@...sando.io>
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 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.

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.

    Andrew