linux-kernel - [PATCH][next] drivers: ipmi: fix off-by-one bounds check that leads to a out-of-bounds write

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Message-Id: <20200114144031.358003-1-colin.king@canonical.com>
Date:   Tue, 14 Jan 2020 14:40:31 +0000
From:   Colin King <colin.king@...onical.com>
To:     Corey Minyard <cminyard@...sta.com>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        vadimp@...lanox.com, Asmaa Mnebhi <Asmaa@...lanox.com>,
        openipmi-developer@...ts.sourceforge.net
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] drivers: ipmi: fix off-by-one bounds check that leads to a out-of-bounds write

From: Colin Ian King <colin.king@...onical.com>

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

diff --git a/drivers/char/ipmi/ipmb_dev_int.c b/drivers/char/ipmi/ipmb_dev_int.c
index 9fdae83e59e0..382b28f1cf2f 100644
--- 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;
-- 
2.24.0