linux-kernel - Re: [PATCH v2] mmc: tmio: avoid concurrent runs of mmc_request

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Date: Tue, 5 Mar 2024 14:48:12 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: linux-renesas-soc@...r.kernel.org, Dirk Behme <dirk.behme@...bosch.com>, 
	stable@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>, 
	Chris Ball <cjb@...top.org>, Guennadi Liakhovetski <g.liakhovetski@....de>, linux-mmc@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mmc: tmio: avoid concurrent runs of mmc_request_done()

On Tue, Mar 5, 2024 at 11:54 AM Wolfram Sang
<wsa+renesas@...g-engineering.com> wrote:
> With the to-be-fixed commit, the reset_work handler cleared 'host->mrq'
> outside of the spinlock protected critical section. That leaves a small
> race window during execution of 'tmio_mmc_reset()' where the done_work
> handler could grab a pointer to the now invalid 'host->mrq'. Both would
> use it to call mmc_request_done() causing problems (see link below).
>
> However, 'host->mrq' cannot simply be cleared earlier inside the
> critical section. That would allow new mrqs to come in asynchronously
> while the actual reset of the controller still needs to be done. So,
> like 'tmio_mmc_set_ios()', an ERR_PTR is used to prevent new mrqs from
> coming in but still avoiding concurrency between work handlers.
>
> Reported-by: Dirk Behme <dirk.behme@...bosch.com>
> Closes: https://lore.kernel.org/all/20240220061356.3001761-1-dirk.behme@de.bosch.com/
> Fixes: df3ef2d3c92c ("mmc: protect the tmio_mmc driver against a theoretical race")
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> Tested-by: Dirk Behme <dirk.behme@...bosch.com>
> Reviewed-by: Dirk Behme <dirk.behme@...bosch.com>
> Cc: stable@...r.kernel.org # 3.0+

Thanks, I gave it a boot run on all boards in my farm, no issues seen.
Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds