linux-kernel - Re: [RFC] taint: add module firmware crash taint support

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Message-ID: <20200508060417.GE11244@42.do-not-panic.com>
Date:   Fri, 8 May 2020 06:04:17 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     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, daniel.vetter@...ll.ch,
        will@...nel.org, mchehab+samsung@...nel.org, kvalo@...eaurora.org,
        davem@...emloft.net, linux-kernel@...r.kernel.org
Subject: Re: [RFC] taint: add module firmware crash taint support

On Thu, May 07, 2020 at 10:47:08PM -0700, Kees Cook wrote:
> On Fri, May 08, 2020 at 02:14:38AM +0000, 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 provide a helper which lets drivers
> > annotate this.
> > 
> > Once this happens, scrapers can easily scrape modules taint flags.
> > This will taint both the kernel and respective calling module.
> > 
> > The new helper module_firmware_crashed() uses LOCKDEP_STILL_OK as
> > this fact should in no way shape or form affect lockdep. This taint
> > is device driver specific.
> > 
> > Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> > ---
> > 
> > Below is the full diff stat of manual inspection throughout the kernel
> > when this happens. My methodology is to just scrape for "crash" and
> > then study the driver a bit to see if indeed it seems like that the
> > firmware crashes there. In *many* cases there is even infrastructure
> > for this, so this is sometimes clearly obvious. Some other times it
> > required a bit of deciphering.
> > 
> > The diff stat below is what I have so far, however the patch below
> > only includes the drivers that start with Q, as they were a source of
> > inspiration for this, and to make this RFC easier to read.
> > 
> > If this seems sensible, I can follow up with the kernel helper first,
> > and then tackle each subsystem independently.
> > 
> > I purposely skipped review of remoteproc and virtualization. That should
> > require its own separate careful review and considerations.
> 
> This all seems reasonable to me. You might need to break these up into
> per-maintainer patches to get appropriate review. Perhaps land the
> infrastructure and some initial patches via netdev and in the next
> release send patches for DRM, media, etc?

Works for me.

I'll give it a few more days for review on the RFC before I shoot out a
series for netdev.

  Luis