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Date:   Thu, 18 May 2023 11:22:14 -0600
From:   Raul E Rangel <rrangel@chromium.org>
To:     Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/7] Input: libps2 - fix aborting PS/2 commands
Message-ID: <ZGZexnCoFLG6J8ob@google.com>
References: <20230511185252.386941-1-dmitry.torokhov@gmail.com>
 <20230511185252.386941-6-dmitry.torokhov@gmail.com>
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On Thu, May 11, 2023 at 11:52:45AM -0700, Dmitry Torokhov wrote:
> When aborting PS/2 command the kernel should [re]set all flags before
> waking up waiters, otherwise waiting thread may read obsolete values
> of flags.
> 
> Reported-by: Raul Rangel <rrangel@chromium.org>
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> ---
>  drivers/input/serio/libps2.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/input/serio/libps2.c b/drivers/input/serio/libps2.c
> index 14b70a78875d..09eb605364bb 100644
> --- a/drivers/input/serio/libps2.c
> +++ b/drivers/input/serio/libps2.c
> @@ -478,15 +478,22 @@ bool ps2_handle_response(struct ps2dev *ps2dev, u8 data)
>  }
>  EXPORT_SYMBOL(ps2_handle_response);
>  
> +/*
> + * Clears state of PS/2 device after communication error by resetting majority
> + * of flags and waking up waiters, if any.
> + */
>  void ps2_cmd_aborted(struct ps2dev *ps2dev)
>  {
> -	if (ps2dev->flags & PS2_FLAG_ACK)
> +	unsigned long old_flags = ps2dev->flags;
> +
> +	/* reset all flags except last nak */
> +	ps2dev->flags &= PS2_FLAG_NAK;
> +
> +	if (old_flags & PS2_FLAG_ACK)
>  		ps2dev->nak = 1;
>  
> -	if (ps2dev->flags & (PS2_FLAG_ACK | PS2_FLAG_CMD))
> +	if (old_flags & (PS2_FLAG_ACK | PS2_FLAG_CMD))
>  		wake_up(&ps2dev->wait);
>  
> -	/* reset all flags except last nack */
> -	ps2dev->flags &= PS2_FLAG_NAK;
>  }
>  EXPORT_SYMBOL(ps2_cmd_aborted);
Reviewed-by: Raul E Rangel <rrangel@chromium.org>