linux-kernel - Re: [PATCH] drivers/firmware_loader: remove list entry before deallocation

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Date:   Mon, 12 Dec 2022 18:52:51 +0100
From:   Michał Lach <michal.lach@...sung.com>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     linux-kernel@...r.kernel.org, russell.h.weight@...el.com,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        ming.lei@...onical.com, tiwai@...e.de
Subject: Re: [PATCH] drivers/firmware_loader: remove list entry before
 deallocation

On 12/12/22 07:04, Luis Chamberlain wrote:
> Hey Michal! Thanks for your patch! I have a few doubts though!

:-)

> To account for not having to deal with specific drivers we have the
> Linux kernel selftests. And so you can test the firmware loader with all
> sorts of crazy situations which any driver could use and try to see
> if you can re-recreate the issue.
> 
> The kernel selftests driver for the firmware loader is in
> lib/test_firmware.c and you can use thetools/testing/selftests/firmware/fw_run_tests.sh
> to run all the tests. To test the firmware fallback alone you can use
> just fw_fallback.sh.
> 
> If you want to just virtualize this and you can also use kdevops [0] and
> enable the firmware loader selftest and use:;
> 
> make menuconfig          #  enable selftests and just the firmware test
> make linux               #  build linux, pick linux-next
> make selftests
> make selftests-firmware
> 
> But this may be something more you can use later once you get your flow
> going. Just compiling the kernel and running the selftest manually with
> fw_fallback.sh should suffice.

Thanks a lot, I had no idea that there is something like this.

> OK so this proves the bug can happen but I'd like to see the full trace
> and the exact kernel version showing that this can happen on a recent
> kernel. Without that I'm not seeing how this can trigger yet.

Unfortunately I cannot provide a trace. The kernel version was 5.15.41 (-stable).

Keeping that in mind, I will try to reproduce this behaviour with in-tree
code and provide proof.

With regards,
Michał