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Subject[PATCH net v3] net/ncsi: handle overflow when incrementing mac address
Date
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 <taoren@fb.com>
---
include/linux/etherdevice.h | 15 +++++++++++++--
net/ncsi/ncsi-rsp.c | 6 +++++-
2 files changed, 18 insertions(+), 3 deletions(-)

Changes in v3:
- squash changes in "etherdevice.h" into this patch.
- fix format issue in function comment.
Changes in v2:
- increment MAC address by calling eth_addr_inc() function.
- validate MAC address before assigning to BMC.

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index e2f3b21cd72a..ac5ca754e362 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -436,8 +436,7 @@ static inline void u64_to_ether_addr(u64 u, u8 *addr)
}

/**
- * eth_addr_dec - Decrement the given MAC address
- *
+ * eth_addr_dec() - Decrement the given MAC address
* @addr: Pointer to a six-byte array containing Ethernet address to decrement
*/
static inline void eth_addr_dec(u8 *addr)
@@ -448,6 +447,18 @@ static inline void eth_addr_dec(u8 *addr)
u64_to_ether_addr(u, 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
diff --git a/net/ncsi/ncsi-rsp.c b/net/ncsi/ncsi-rsp.c
index dc07fcc7938e..802db01e3075 100644
--- 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(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]++;
+ 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");
--
2.17.1
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