Re: [RFC] taint: add module firmware crash taint support

From: Rafael Aquini <aquini@redhat.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: jeyu@kernel.org, akpm@linux-foundation.org, arnd@arndb.de,
	rostedt@goodmis.org, mingo@redhat.com, cai@lca.pw,
	dyoung@redhat.com, bhe@redhat.com, peterz@infradead.org,
	tglx@linutronix.de, gpiccoli@canonical.com, pmladek@suse.com,
	tiwai@suse.de, schlad@suse.de, andriy.shevchenko@linux.intel.com,
	keescook@chromium.org, daniel.vetter@ffwll.ch, will@kernel.org,
	mchehab+samsung@kernel.org, kvalo@codeaurora.org,
	davem@davemloft.net, linux-kernel@vger.kernel.org
Subject: Re: [RFC] taint: add module firmware crash taint support
Date: Fri, 8 May 2020 10:04:15 -0400	[thread overview]
Message-ID: <20200508140415.GC367616@optiplex-lnx> (raw)
In-Reply-To: <20200508021438.4373-1-mcgrof@kernel.org>

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.
> 
...
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 04a5885cec1b..19e1541c82c7 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -601,7 +601,8 @@ extern enum system_states {
>  #define TAINT_LIVEPATCH			15
>  #define TAINT_AUX			16
>  #define TAINT_RANDSTRUCT		17
> -#define TAINT_FLAGS_COUNT		18
> +#define TAINT_FIRMWARE_CRASH		18
> +#define TAINT_FLAGS_COUNT		19
>  

As others have already mentioned (and I guess it was your idea too)
it would be nicer to split the changes into a set.

We also will need to update Documentation/admin-guide/tainted-kernels.rst
to reflect the inclusion of this new flag.

-- Rafael