netdev - [PATCH net] net/ncsi: handle overflow when incrementing mac address

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190422172754.1011894-1-taoren@fb.com>
Date:   Mon, 22 Apr 2019 10:27:54 -0700
From:   Tao Ren <taoren@...com>
To:     Samuel Mendoza-Jonas <sam@...dozajonas.com>,
        "David S . Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>, <openbmc@...ts.ozlabs.org>
CC:     Tao Ren <taoren@...com>
Subject: [PATCH net] net/ncsi: handle overflow when incrementing mac address

Previously BMC's MAC address is calculated by simply adding 1 to the
last byte of network controller's MAC address, and it produces incorrect
result when network controller's MAC address ends with 0xFF.
The problem is fixed by detecting integer overflow when incrementing MAC
address and adding the carry bit (if any) to the next/left bytes of the
MAC address.

Signed-off-by: Tao Ren <taoren@...com>
---
 net/ncsi/ncsi-rsp.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/ncsi/ncsi-rsp.c b/net/ncsi/ncsi-rsp.c
index dc07fcc7938e..eb42bbdb7501 100644
--- a/net/ncsi/ncsi-rsp.c
+++ b/net/ncsi/ncsi-rsp.c
@@ -658,7 +658,8 @@ static int ncsi_rsp_handler_oem_bcm_gma(struct ncsi_request *nr)
 	const struct net_device_ops *ops = ndev->netdev_ops;
 	struct ncsi_rsp_oem_pkt *rsp;
 	struct sockaddr saddr;
-	int ret = 0;
+	int ret, offset;
+	u16 carry = 1;
 
 	/* Get the response header */
 	rsp = (struct ncsi_rsp_oem_pkt *)skb_network_header(nr->rsp);
@@ -667,7 +668,12 @@ static int ncsi_rsp_handler_oem_bcm_gma(struct ncsi_request *nr)
 	ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;
 	memcpy(saddr.sa_data, &rsp->data[BCM_MAC_ADDR_OFFSET], ETH_ALEN);
 	/* Increase mac address by 1 for BMC's address */
-	saddr.sa_data[ETH_ALEN - 1]++;
+	offset = ETH_ALEN - 1;
+	do {
+		carry += (u8)saddr.sa_data[offset];
+		saddr.sa_data[offset] = (char)carry;
+		carry = carry >> 8;
+	} while (carry != 0 && --offset >= 0);
 	ret = ops->ndo_set_mac_address(ndev, &saddr);
 	if (ret < 0)
 		netdev_warn(ndev, "NCSI: 'Writing mac address to device failed\n");
-- 
2.17.1