Commit 88b4116e authored by George Cherian's avatar George Cherian Committed by Wolfram Sang
Browse files

i2c: xlp9xx: Make sure the transfer size is not more than I2C_SMBUS_BLOCK_SIZE 



For SMBus transactions the max permissible transfer size is
I2C_SMBUS_BLOCK_SIZE. It is possible that some clients might
not follow it strictly occasionally.
This would lead to stack corruption if the driver copies more than
I2C_SMBUS_BLOCK_SIZE bytes. Add a check to avoid such conditions.

Signed-off-by: default avatarJayachandran C <jnair@caviumnetworks.com>
Signed-off-by: default avatarGeorge Cherian <george.cherian@cavium.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 8d504d80

drivers/i2c/busses/i2c-xlp9xx.c

+24 −13
Original line number Diff line number Diff line
@@ -172,6 +172,8 @@ static void xlp9xx_i2c_update_rlen(struct xlp9xx_i2c_dev *priv) 
	len = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_FIFOWCNT) &

				  XLP9XX_I2C_FIFO_WCNT_MASK;

	len = max_t(u32, priv->msg_len, len + 4);

	if (len >= I2C_SMBUS_BLOCK_MAX + 2)

		return;

	val = (val & ~XLP9XX_I2C_CTRL_MCTLEN_MASK) |

			(len << XLP9XX_I2C_CTRL_MCTLEN_SHIFT);

	xlp9xx_write_i2c_reg(priv, XLP9XX_I2C_CTRL, val);
@@ -189,14 +191,20 @@ static void xlp9xx_i2c_drain_rx_fifo(struct xlp9xx_i2c_dev *priv) 
	if (priv->len_recv) {

		/* read length byte */

		rlen = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_MRXFIFO);

		if (rlen > I2C_SMBUS_BLOCK_MAX || rlen == 0) {

			rlen = 0;	/*abort transfer */

			priv->msg_buf_remaining = 0;

			priv->msg_len = 0;

		} else {

			*buf++ = rlen;

			if (priv->client_pec)

			++rlen;

				++rlen; /* account for error check byte */

			/* update remaining bytes and message length */

			priv->msg_buf_remaining = rlen;

			priv->msg_len = rlen + 1;

		priv->len_recv = false;

		}

		xlp9xx_i2c_update_rlen(priv);

		priv->len_recv = false;

	} else {

		len = min(priv->msg_buf_remaining, len);

		for (i = 0; i < len; i++, buf++)
@@ -315,10 +323,6 @@ static int xlp9xx_i2c_xfer_msg(struct xlp9xx_i2c_dev *priv, struct i2c_msg *msg, 
	xlp9xx_write_i2c_reg(priv, XLP9XX_I2C_MFIFOCTRL,

			     XLP9XX_I2C_MFIFOCTRL_RST);



	/* set FIFO threshold if reading */

	if (priv->msg_read)

		xlp9xx_i2c_update_rx_fifo_thres(priv);



	/* set slave addr */

	xlp9xx_write_i2c_reg(priv, XLP9XX_I2C_SLAVEADDR,

			     (msg->addr << XLP9XX_I2C_SLAVEADDR_ADDR_SHIFT) |
@@ -337,9 +341,13 @@ static int xlp9xx_i2c_xfer_msg(struct xlp9xx_i2c_dev *priv, struct i2c_msg *msg, 
		val &= ~XLP9XX_I2C_CTRL_ADDMODE;



	priv->len_recv = msg->flags & I2C_M_RECV_LEN;

	len = priv->len_recv ? XLP9XX_I2C_FIFO_SIZE : msg->len;

	len = priv->len_recv ? I2C_SMBUS_BLOCK_MAX + 2 : msg->len;

	priv->client_pec = msg->flags & I2C_CLIENT_PEC;



	/* set FIFO threshold if reading */

	if (priv->msg_read)

		xlp9xx_i2c_update_rx_fifo_thres(priv);



	/* set data length to be transferred */

	val = (val & ~XLP9XX_I2C_CTRL_MCTLEN_MASK) |

	      (len << XLP9XX_I2C_CTRL_MCTLEN_SHIFT);
@@ -393,8 +401,11 @@ static int xlp9xx_i2c_xfer_msg(struct xlp9xx_i2c_dev *priv, struct i2c_msg *msg, 
	}



	/* update msg->len with actual received length */

	if (msg->flags & I2C_M_RECV_LEN)

	if (msg->flags & I2C_M_RECV_LEN) {

		if (!priv->msg_len)

			return -EPROTO;

		msg->len = priv->msg_len;

	}

	return 0;

}

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