linux-kernel - Re: [PATCH 03/12] can: kvaser_usb: Fix possible completions during init

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Date:   Sat, 28 May 2022 09:34:57 +0200
From:   Jimmy Assarsson <extja@...ser.com>
To:     Anssi Hannula <anssi.hannula@...wise.fi>
Cc:     linux-can@...r.kernel.org, Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/12] can: kvaser_usb: Fix possible completions during
 init_completion

On 5/16/22 15:47, Anssi Hannula wrote:
> kvaser_usb uses completions to signal when a response event is received
> for outgoing commands.
> 
> However, it uses init_completion() to reinitialize the start_comp and
> stop_comp completions before sending the start/stop commands.
> 
> In case the device sends the corresponding response just before the
> actual command is sent, complete() may be called concurrently with
> init_completion() which is not safe.
> 
> This might be triggerable even with a properly functioning device by
> stopping the interface (CMD_STOP_CHIP) just after it goes bus-off (which
> also causes the driver to send CMD_STOP_CHIP when restart-ms is off),
> but that was not tested.
> 
> Fix the issue by using reinit_completion() instead.
> 
> Fixes: 080f40a6fa28 ("can: kvaser_usb: Add support for Kvaser CAN/USB devices")
> Signed-off-by: Anssi Hannula <anssi.hannula@...wise.fi>

Looks good to me.
Tested-by: Jimmy Assarsson <extja@...ser.com>

> ---
>   drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c | 4 ++--
>   drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c  | 4 ++--
>   2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
> index 4e90a4b7f95a..b0094f162964 100644
> --- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
> +++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_hydra.c
> @@ -1869,7 +1869,7 @@ static int kvaser_usb_hydra_start_chip(struct kvaser_usb_net_priv *priv)
>   {
>   	int err;
>   
> -	init_completion(&priv->start_comp);
> +	reinit_completion(&priv->start_comp);
>   
>   	err = kvaser_usb_hydra_send_simple_cmd(priv->dev, CMD_START_CHIP_REQ,
>   					       priv->channel);
> @@ -1887,7 +1887,7 @@ static int kvaser_usb_hydra_stop_chip(struct kvaser_usb_net_priv *priv)
>   {
>   	int err;
>   
> -	init_completion(&priv->stop_comp);
> +	reinit_completion(&priv->stop_comp);
>   
>   	/* Make sure we do not report invalid BUS_OFF from CMD_CHIP_STATE_EVENT
>   	 * see comment in kvaser_usb_hydra_update_state()
> diff --git a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
> index d9f40b9702a5..09ade66256b2 100644
> --- a/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
> +++ b/drivers/net/can/usb/kvaser_usb/kvaser_usb_leaf.c
> @@ -1300,7 +1300,7 @@ static int kvaser_usb_leaf_start_chip(struct kvaser_usb_net_priv *priv)
>   {
>   	int err;
>   
> -	init_completion(&priv->start_comp);
> +	reinit_completion(&priv->start_comp);
>   
>   	err = kvaser_usb_leaf_send_simple_cmd(priv->dev, CMD_START_CHIP,
>   					      priv->channel);
> @@ -1318,7 +1318,7 @@ static int kvaser_usb_leaf_stop_chip(struct kvaser_usb_net_priv *priv)
>   {
>   	int err;
>   
> -	init_completion(&priv->stop_comp);
> +	reinit_completion(&priv->stop_comp);
>   
>   	err = kvaser_usb_leaf_send_simple_cmd(priv->dev, CMD_STOP_CHIP,
>   					      priv->channel);