netdev - Re: [RFC 1/2] devlink: add simple fw crash helpers

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Message-ID: <20200525090749.GJ1634618@smile.fi.intel.com>
Date:   Mon, 25 May 2020 12:07:49 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Steve deRosier <derosier@...il.com>
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Johannes Berg <johannes@...solutions.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Ben Greear <greearb@...delatech.com>, 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,
        Takashi Iwai <tiwai@...e.de>, schlad@...e.de,
        Kees Cook <keescook@...omium.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>, will@...nel.org,
        mchehab+samsung@...nel.org, Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        ath10k@...ts.infradead.org, jiri@...nulli.us,
        briannorris@...omium.org
Subject: Re: [RFC 1/2] devlink: add simple fw crash helpers

On Fri, May 22, 2020 at 04:23:55PM -0700, Steve deRosier wrote:
> On Fri, May 22, 2020 at 2:51 PM Luis Chamberlain <mcgrof@...nel.org> wrote:

> I had to go RTFM re: kernel taints because it has been a very long
> time since I looked at them. It had always seemed to me that most were
> caused by "kernel-unfriendly" user actions.  The most famous of course
> is loading proprietary modules, out-of-tree modules, forced module
> loads, etc...  Honestly, I had forgotten the large variety of uses of
> the taint flags. For anyone who hasn't looked at taints recently, I
> recommend: https://www.kernel.org/doc/html/latest/admin-guide/tainted-kernels.html
> 
> In light of this I don't object to setting a taint on this anymore.
> I'm a little uneasy, but I've softened on it now, and now I feel it
> depends on implementation.
> 
> Specifically, I don't think we should set a taint flag when a driver
> easily handles a routine firmware crash and is confident that things
> have come up just fine again. In other words, triggering the taint in
> every driver module where it spits out a log comment that it had a
> firmware crash and had to recover seems too much. Sure, firmware
> shouldn't crash, sure it should be open source so we can fix it,
> whatever...

While it may sound idealistic the firmware for the end-user, and even for mere
kernel developer like me, is a complete blackbox which has more access than
root user in the kernel. We have tons of firmwares and each of them potentially
dangerous beast. As a user I really care about my data and privacy (hacker can
oops a firmware in order to set a specific vector attack). So, tainting kernel
is _a least_ we can do there, the strict rules would be to reboot immediately.

> those sort of wishful comments simply ignore reality and
> our ability to affect effective change.

We can encourage users not to buy cheap crap for the starter.

> A lot of WiFi firmware crashes
> and for well-known cases the drivers handle them well. And in some
> cases, not so well and that should be a place the driver should detect
> and thus raise a red flag.  If a WiFi firmware crash can bring down
> the kernel, there's either a major driver bug or some very funky
> hardware crap going on. That sort of thing we should be able to
> detect, mark with a taint (or something), and fix if within our sphere
> of influence. I guess what it comes down to me is how aggressive we
> are about setting the flag.

-- 
With Best Regards,
Andy Shevchenko