[PATCH 5.0 83/89] net/ncsi: handle overflow when incrementing mac address

[Greg Kroah-Hartman]

From: Tao Ren <tao...@fb.com>

[ Upstream commit 1c5c12ee308aacf635c8819cd4baa3bd58f8a8b7 ]

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 can be fixed by calling eth_addr_inc() function to increment
MAC address; besides, the MAC address is also validated before assigning
to BMC.

Fixes: cb10c7c0dfd9 ("net/ncsi: Add NCSI Broadcom OEM command")
Signed-off-by: Tao Ren <tao...@fb.com>
Acked-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Acked-by: Samuel Mendoza-Jonas <s...@mendozajonas.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 include/linux/etherdevice.h |   12 ++++++++++++
 net/ncsi/ncsi-rsp.c         |    6 +++++-
 2 files changed, 17 insertions(+), 1 deletion(-)

--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -448,6 +448,18 @@ static inline void eth_addr_dec(u8 *addr
 }
 
 /**
+ * eth_addr_inc() - Increment the given MAC address.
+ * @addr: Pointer to a six-byte array containing Ethernet address to increment.
+ */
+static inline void eth_addr_inc(u8 *addr)
+{
+       u64 u = ether_addr_to_u64(addr);
+
+       u++;
+       u64_to_ether_addr(u, addr);
+}
+
+/**
  * is_etherdev_addr - Tell if given Ethernet address belongs to the device.
  * @dev: Pointer to a device structure
  * @addr: Pointer to a six-byte array containing the Ethernet address
--- a/net/ncsi/ncsi-rsp.c
+++ b/net/ncsi/ncsi-rsp.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/netdevice.h>
+#include <linux/etherdevice.h>
 #include <linux/skbuff.h>
 
 #include <net/ncsi.h>
@@ -667,7 +668,10 @@ static int ncsi_rsp_handler_oem_bcm_gma(
        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]++;
+       eth_addr_inc((u8 *)saddr.sa_data);
+       if (!is_valid_ether_addr((const u8 *)saddr.sa_data))
+               return -ENXIO;
+
        ret = ops->ndo_set_mac_address(ndev, &saddr);
        if (ret < 0)
                netdev_warn(ndev, "NCSI: 'Writing mac address to device 
failed\n");