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: 0ba0c3c5d1c1 ("ipmi:ipmb: Add initial support for IPMI over IPMB")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Message-Id: <20211005151611.305383-1-colin.king@canonical.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

diff --git a/drivers/char/ipmi/ipmi_ipmb.c b/drivers/char/ipmi/ipmi_ipmb.c
index 742ae10166af544da4ecc848d13304ca5023f991..856e432fa04cbbca94c99b9f5d0a3b5dd17dc22c 100644 (file)
--- a/drivers/char/ipmi/ipmi_ipmb.c
+++ b/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;