Re: [PATCH v3 1/3] usb: typec: ucsi: Limit read size on v1.2

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Fri, Jan 26, 2024 at 10:39:07AM -0800, Abhishek Pandit-Subedi wrote:
> Between UCSI 1.2 and UCSI 2.0, the size of the MESSAGE_IN region was
> increased from 16 to 256. In order to avoid overflowing reads for older
> systems, add a mechanism to use the read UCSI version to truncate read
> sizes on UCSI v1.2.
> 
> Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

> ---
> Tested on 6.6 kernel. Dmesg output from this change:
> [  105.058162] ucsi_um_test ucsi_um_test_device.0: Registered UCSI
> interface with version 3.0.0
> 
> 
> (no changes since v2)
> 
> Changes in v2:
>   - Changed log message to DEBUG
> 
>  drivers/usb/typec/ucsi/ucsi.c | 26 ++++++++++++++++++++++++--
>  drivers/usb/typec/ucsi/ucsi.h | 11 +++++++++++
>  2 files changed, 35 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index 5392ec698959..a35056ee3e96 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -36,6 +36,19 @@
>   */
>  #define UCSI_SWAP_TIMEOUT_MS	5000
>  
> +static int ucsi_read_message_in(struct ucsi *ucsi, void *buf,
> +					  size_t buf_size)
> +{
> +	/*
> +	 * Below UCSI 2.0, MESSAGE_IN was limited to 16 bytes. Truncate the
> +	 * reads here.
> +	 */
> +	if (ucsi->version <= UCSI_VERSION_1_2)
> +		buf_size = min_t(size_t, 16, buf_size);
> +
> +	return ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, buf, buf_size);
> +}
> +
>  static int ucsi_acknowledge_command(struct ucsi *ucsi)
>  {
>  	u64 ctrl;
> @@ -72,7 +85,7 @@ static int ucsi_read_error(struct ucsi *ucsi)
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, &error, sizeof(error));
> +	ret = ucsi_read_message_in(ucsi, &error, sizeof(error));
>  	if (ret)
>  		return ret;
>  
> @@ -170,7 +183,7 @@ int ucsi_send_command(struct ucsi *ucsi, u64 command,
>  	length = ret;
>  
>  	if (data) {
> -		ret = ucsi->ops->read(ucsi, UCSI_MESSAGE_IN, data, size);
> +		ret = ucsi_read_message_in(ucsi, data, size);
>  		if (ret)
>  			goto out;
>  	}
> @@ -1556,6 +1569,15 @@ int ucsi_register(struct ucsi *ucsi)
>  	if (!ucsi->version)
>  		return -ENODEV;
>  
> +	/*
> +	 * Version format is JJ.M.N (JJ = Major version, M = Minor version,
> +	 * N = sub-minor version).
> +	 */
> +	dev_dbg(ucsi->dev, "Registered UCSI interface with version %x.%x.%x",
> +		UCSI_BCD_GET_MAJOR(ucsi->version),
> +		UCSI_BCD_GET_MINOR(ucsi->version),
> +		UCSI_BCD_GET_SUBMINOR(ucsi->version));
> +
>  	queue_delayed_work(system_long_wq, &ucsi->work, 0);
>  
>  	ucsi_debugfs_register(ucsi);
> diff --git a/drivers/usb/typec/ucsi/ucsi.h b/drivers/usb/typec/ucsi/ucsi.h
> index 6478016d5cb8..bec920fa6b8a 100644
> --- a/drivers/usb/typec/ucsi/ucsi.h
> +++ b/drivers/usb/typec/ucsi/ucsi.h
> @@ -23,6 +23,17 @@ struct dentry;
>  #define UCSI_CONTROL			8
>  #define UCSI_MESSAGE_IN			16
>  #define UCSI_MESSAGE_OUT		32
> +#define UCSIv2_MESSAGE_OUT		272
> +
> +/* UCSI versions */
> +#define UCSI_VERSION_1_2	0x0120
> +#define UCSI_VERSION_2_0	0x0200
> +#define UCSI_VERSION_2_1	0x0210
> +#define UCSI_VERSION_3_0	0x0300
> +
> +#define UCSI_BCD_GET_MAJOR(_v_)		(((_v_) >> 8) & 0xFF)
> +#define UCSI_BCD_GET_MINOR(_v_)		(((_v_) >> 4) & 0x0F)
> +#define UCSI_BCD_GET_SUBMINOR(_v_)	((_v_) & 0x0F)
>  
>  /* Command Status and Connector Change Indication (CCI) bits */
>  #define UCSI_CCI_CONNECTOR(_c_)		(((_c_) & GENMASK(7, 1)) >> 1)
> -- 
> 2.43.0.429.g432eaa2c6b-goog

-- 
heikki