netdev - [PATCH net 14/15] can: mcp251xfd: mcp251xfd_register_get_dev_id(): use correct length to read dev

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Date:   Mon,  4 Jul 2022 14:26:12 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH net 14/15] can: mcp251xfd: mcp251xfd_register_get_dev_id(): use correct length to read dev_id

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.

Fix the length of the SPI transfer to read the device ID register
only.

Link: https://lore.kernel.org/all/20220616094914.244440-1-mkl@pengutronix.de
Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Reported-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.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