Re: [PATCH] usb: typec: ucsi: Set ucsi->connector before enabling notifications

[Peter Chen]

On 26-09-23 11:34:34, Uttkarsh Aggarwal wrote:
> In ucsi_init(), ucsi->connector is assigned only after the
> UCSI_SET_NOTIFICATION_ENABLE command completes. But once that command
> is sent, the PPM is free to raise a connector change notification at
> any time, which is handled through:
> 
>     ucsi_notify_common() -> ucsi_connector_change()
> 
> ucsi_connector_change() indexes into ucsi->connector to get the
> connector and schedule its work item. If this notification arrives
> before ucsi_init() reaches the "ucsi->connector = connector;" line,
> ucsi->connector is still NULL and the driver crashes dereferencing it.

If you have logs for it, you can attach it.

> 
> Fix this by setting ucsi->connector right after the connectors are
> registered, before notifications are enabled, so it is always valid
> by the time a connector change event can be delivered. Also clear
> ucsi->connector in the err_unregister path so it isn't left pointing
> at freed memory if a later step in ucsi_init() fails.
> 
> Signed-off-by: Uttkarsh Aggarwal <uttkarsh.aggarwal@xxxxxxxxxxxxxxxx>

It seems it is a bug. You could add Fixed-by tag and Cc to stable tree.

Peter
> ---
>  drivers/usb/typec/ucsi/ucsi.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index bef3f9b71d71..8f7b73a9f4f4 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -2122,6 +2122,14 @@ static int ucsi_init(struct ucsi *ucsi)
>  			goto err_unregister;
>  	}
>  
> +	/*
> +	 * Set ucsi->connector before enabling notifications. A connector
> +	 * change event can be handled as soon as the notifications are
> +	 * enabled below, and ucsi_connector_change() indexes into
> +	 * ucsi->connector, so it must not be NULL at that point.
> +	 */
> +	ucsi->connector = connector;
> +
>  	/* Enable all supported notifications */
>  	ntfy = ucsi_get_supported_notifications(ucsi);
>  	command = UCSI_SET_NOTIFICATION_ENABLE | ntfy;
> @@ -2129,7 +2137,6 @@ static int ucsi_init(struct ucsi *ucsi)
>  	if (ret < 0)
>  		goto err_unregister;
>  
> -	ucsi->connector = connector;
>  	ucsi->ntfy = ntfy;
>  
>  	mutex_lock(&ucsi->ppm_lock);
> @@ -2143,6 +2150,7 @@ static int ucsi_init(struct ucsi *ucsi)
>  	return 0;
>  
>  err_unregister:
> +	ucsi->connector = NULL;
>  	for (con = connector; con->port; con++)
>  		ucsi_unregister_port(con);
>  	for (i = 0; i < ucsi->cap.num_connectors; i++)
> -- 
> 2.34.1
> 
> 

-- 

Thanks,
Peter Chen