[PATCH] can: mcp251xfd: mcp251xfd_register_get_dev_id(): use correct length to read dev_id

[PATCH] can: mcp251xfd: mcp251xfd_register_get_dev_id(): use correct length to read dev_id

[Marc Kleine-Budde]

The device ID register is 32 bits wide. The driver uses incorrectly
the size of a pointer to a u32 to calculate the length of the SPI
transfer. This results in a read of 2 registers on 64 bit platforms.
This is no problem on the Linux side, as the RX buffer of the SPI
transfer is large enough. In the mpc251xfd chip this results in the
read of an undocumented register. So far no problems were observed.

This patch fixes the length of the SPI transfer to read the device ID
register only.

Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
 drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index 34b160024ce3..3160881e89d9 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -1778,7 +1778,7 @@ mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv, u32 *dev_id,
 	xfer[0].len = sizeof(buf_tx->cmd);
 	xfer[0].speed_hz = priv->spi_max_speed_hz_slow;
 	xfer[1].rx_buf = buf_rx->data;
-	xfer[1].len = sizeof(dev_id);
+	xfer[1].len = sizeof(*dev_id);
 	xfer[1].speed_hz = priv->spi_max_speed_hz_fast;
 
 	mcp251xfd_spi_cmd_read_nocrc(&buf_tx->cmd, MCP251XFD_REG_DEVID);
-- 
2.35.1

Re: [PATCH] can: mcp251xfd: mcp251xfd_register_get_dev_id(): use correct length to read dev_id

[Manivannan Sadhasivam]

On Thu, Jun 16, 2022 at 11:49:14AM +0200, Marc Kleine-Budde wrote:
> The device ID register is 32 bits wide. The driver uses incorrectly
> the size of a pointer to a u32 to calculate the length of the SPI
> transfer. This results in a read of 2 registers on 64 bit platforms.
> This is no problem on the Linux side, as the RX buffer of the SPI
> transfer is large enough. In the mpc251xfd chip this results in the
> read of an undocumented register. So far no problems were observed.
> 
> This patch fixes the length of the SPI transfer to read the device ID
> register only.
> 
> Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Thanks,
Mani

> ---
>  drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> index 34b160024ce3..3160881e89d9 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> @@ -1778,7 +1778,7 @@ mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv, u32 *dev_id,
>  	xfer[0].len = sizeof(buf_tx->cmd);
>  	xfer[0].speed_hz = priv->spi_max_speed_hz_slow;
>  	xfer[1].rx_buf = buf_rx->data;
> -	xfer[1].len = sizeof(dev_id);
> +	xfer[1].len = sizeof(*dev_id);
>  	xfer[1].speed_hz = priv->spi_max_speed_hz_fast;
>  
>  	mcp251xfd_spi_cmd_read_nocrc(&buf_tx->cmd, MCP251XFD_REG_DEVID);
> -- 
> 2.35.1
> 
> 

-- 
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