drivers: ipmi: fix off-by-one bounds check that leads to a out-of-bounds write

The end of buffer check is off-by-one since the check is against
an index that is pre-incremented before a store to buf[]. Fix this
adjusting the bounds check appropriately.

Addresses-Coverity: ("Out-of-bounds write")
Fixes: 51bd6f291583 ("Add support for IPMB driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Message-Id: <20200114144031.358003-1-colin.king@canonical.com>
Reviewed-by: Asmaa Mnebhi <asmaa@mellanox.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

diff --git a/drivers/char/ipmi/ipmb_dev_int.c b/drivers/char/ipmi/ipmb_dev_int.c
index 9fdae83e59e02d11cff0c3c6d5f506a7c9e2260e..382b28f1cf2f6daf922236e827a2abce1bc73940 100644 (file)
--- a/drivers/char/ipmi/ipmb_dev_int.c
+++ b/drivers/char/ipmi/ipmb_dev_int.c
@@ -279,7 +279,7 @@ static int ipmb_slave_cb(struct i2c_client *client,
                break;
 
        case I2C_SLAVE_WRITE_RECEIVED:
-               if (ipmb_dev->msg_idx >= sizeof(struct ipmb_msg))
+               if (ipmb_dev->msg_idx >= sizeof(struct ipmb_msg) - 1)
                        break;
 
                buf[++ipmb_dev->msg_idx] = *val;