[PATCH] Modify is_zero_ether_addr() to handle byte-aligned addresses

[Petri Gynther <pgynther@google.com>]

$ iwconfig mlan0 essid MySSID
[   36.930000] Path: /sbin/iwconfig
[   36.930000] CPU: 0 PID: 203 Comm: iwconfig Not tainted 4.7.0 #2
[   36.940000] task: 866f83a0 ti: 866a6000 task.ti: 866a6000
[   36.940000]
[ECR   ]: 0x00230400 => Misaligned r/w from 0x8677f403
[   36.960000] [EFA   ]: 0x8677f403
[   36.960000] [BLINK ]: mwifiex_scan_networks+0x17a/0x198c [mwifiex]
[   36.960000] [ERET  ]: mwifiex_scan_networks+0x18a/0x198c [mwifiex]
[   36.980000] [STAT32]: 0x00000206 : K         E2 E1
[   36.980000] BTA: 0x700736e2   SP: 0x866a7d0c  FP: 0x5faddc84
[   37.000000] LPS: 0x806a37ec  LPE: 0x806a37fa LPC: 0x00000000
[   37.000000] r00: 0x8677f401  r01: 0x8668aa08 r02: 0x00000001
r03: 0x00000000 r04: 0x8668b600 r05: 0x8677f406
r06: 0x8702b600 r07: 0x00000000 r08: 0x8702b600
r09: 0x00000000 r10: 0x870b3b00 r11: 0x00000000
r12: 0x00000000
[   37.040000]
[   37.040000] Stack Trace:
[   37.040000]   mwifiex_scan_networks+0x18a/0x198c [mwifiex]

Root cause:
mwifiex driver calls is_zero_ether_addr() against byte-aligned address:

drivers/net/wireless/marvell/mwifiex/fw.h:
struct mwifiex_scan_cmd_config {
        /*
         *  BSS mode to be sent in the firmware command
         */
        u8 bss_mode;

        /* Specific BSSID used to filter scan results in the firmware */
        u8 specific_bssid[ETH_ALEN];

        ...
} __packed;

drivers/net/wireless/marvell/mwifiex/scan.c:
mwifiex_config_scan(..., struct mwifiex_scan_cmd_config *scan_cfg_out, ...)
        ...
        if (adapter->ext_scan &&
            !is_zero_ether_addr(scan_cfg_out->specific_bssid)) {
            ...
        }

Since firmware-related struct mwifiex_scan_cmd_config cannot be changed,
modify is_zero_ether_addr() to handle byte-aligned addresses.

Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Joe Perches <joe@perches.com>
Cc: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Petri Gynther <pgynther@google.com>
---
 include/linux/etherdevice.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/etherdevice.h b/include/linux/etherdevice.h
index 37ff4a6..0cfd243 100644
--- a/include/linux/etherdevice.h
+++ b/include/linux/etherdevice.h
@@ -90,11 +90,13 @@ static inline bool is_link_local_ether_addr(const u8 *addr)
  * @addr: Pointer to a six-byte array containing the Ethernet address
  *
  * Return true if the address is all zeroes.
- *
- * Please note: addr must be aligned to u16.
  */
 static inline bool is_zero_ether_addr(const u8 *addr)
 {
+	if ((u32)addr & 0x1)
+		return (addr[0] | addr[1] | addr[2] | addr[3] | addr[4] |
+			addr[5]) == 0;
+
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
 	return ((*(const u32 *)addr) | (*(const u16 *)(addr + 4))) == 0;
 #else
-- 
2.8.0.rc3.226.g39d4020