Re: [PATCH v2] mmc: tmio: avoid concurrent runs of mmc_request_done()

[Geert Uytterhoeven]

On Tue, Mar 5, 2024 at 11:54 AM Wolfram Sang
<wsa+renesas@xxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxx>
> Closes: https://lore.kernel.org/all/20240220061356.3001761-1-dirk.behme@xxxxxxxxxxxx/
> Fixes: df3ef2d3c92c ("mmc: protect the tmio_mmc driver against a theoretical race")
> Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
> Tested-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
> Reviewed-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # 3.0+

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

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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