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Date:   Thu, 7 May 2020 22:47:08 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Luis Chamberlain <mcgrof@kernel.org>
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Subject: Re: [RFC] taint: add module firmware crash taint support
Message-ID: <202005072244.F2E0286@keescook>
References: <20200508021438.4373-1-mcgrof@kernel.org>
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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@kernel.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?

-- 
Kees Cook