[PATCH 5.5 47/80] drivers: ipmi: fix off-by-one bounds check that leads to a out-of-bounds write

[Greg Kroah-Hartman]

From: Colin Ian King <colin.king@xxxxxxxxxxxxx>

commit e0354d147e5889b5faa12e64fa38187aed39aad4 upstream.

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@xxxxxxxxxxxxx>
Message-Id: <20200114144031.358003-1-colin.king@xxxxxxxxxxxxx>
Reviewed-by: Asmaa Mnebhi <asmaa@xxxxxxxxxxxx>
Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/ipmi/ipmb_dev_int.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/ipmi/ipmb_dev_int.c
+++ b/drivers/char/ipmi/ipmb_dev_int.c
@@ -253,7 +253,7 @@ static int ipmb_slave_cb(struct i2c_clie
 		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;