ipmi: ipmb: Fix off-by-one size check on rcvlen

There is an off-by-one bounds check on the rcvlen causing a potential
out of bounds write on iidev->rcvmsg. Fix this by using the >= operator
on the bounds check rather than the > operator.

Addresses-Coverity: ("Out-of-bounds write")
Fixes: 0ba0c3c ("ipmi:ipmb: Add initial support for IPMI over IPMB")
Signed-off-by: Colin Ian King <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Corey Minyard <[email protected]>

Author: Colin Ian King

drivers/char/ipmi/ipmi_ipmb.c

@@ -192,7 +192,7 @@ static int ipmi_ipmb_slave_cb(struct i2c_client *client,
 		break;
 
 	case I2C_SLAVE_WRITE_RECEIVED:
-		if (iidev->rcvlen > sizeof(iidev->rcvmsg))
+		if (iidev->rcvlen >= sizeof(iidev->rcvmsg))
 			iidev->overrun = true;
 		else
 			iidev->rcvmsg[iidev->rcvlen++] = *val;