linux-kernel - Re: [PATCH] input: fix data race __ps2

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Date:	Fri, 25 Sep 2015 13:38:11 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	dmitry.torokhov@...il.com
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	andreyknvl@...gle.com, kcc@...gle.com, glider@...gle.com,
	ktsan@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] input: fix data race __ps2_command

On Monday 07 September 2015 16:04:35 Dmitry Vyukov wrote:
> The data race happens on ps2dev->cmdcnt and ps2dev->cmdbuf contents.
> __ps2_command reads that data concurrently with the interrupt handler.
> As the result, for example, if a response arrives just after the
> timeout, __ps2_command can copy out garbage from ps2dev->cmdbuf
> but then see that ps2dev->cmdcnt is 0 and return success.
> 
> Stop the interrupt handler with serio_pause_rx() before
> reading the results.
> 
> The data race was found with KernelThreadSanitizer (KTSAN).
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
> ---
>  drivers/input/serio/libps2.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/input/serio/libps2.c b/drivers/input/serio/libps2.c
> index 7551699..8f93336 100644
> --- a/drivers/input/serio/libps2.c
> +++ b/drivers/input/serio/libps2.c
> @@ -234,17 +234,19 @@ int __ps2_command(struct ps2dev *ps2dev, unsigned char *param, int command)
>  				   !(ps2dev->flags & PS2_FLAG_CMD), timeout);
>  	}
>  
> +	serio_pause_rx(ps2dev->serio);
>  	if (param)
>  		for (i = 0; i < receive; i++)
>  			param[i] = ps2dev->cmdbuf[(receive - 1) - i];
>  
>  	if (ps2dev->cmdcnt && (command != PS2_CMD_RESET_BAT || ps2dev->cmdcnt != 1))
> -		goto out;
> -
> +		goto out_paused;
>  	rc = 0;
> +	goto out_paused;
>  
>   out:
>  	serio_pause_rx(ps2dev->serio);
> +out_paused:
>  	ps2dev->flags = 0;
>  	serio_continue_rx(ps2dev->serio);
>  

Hi! Was this patch queued? Or is there any problem with it? Because I
did not see any response for more weeks on any mailing list.

-- 
Pali Rohár
pali.rohar@...il.com
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