linux-kernel - [PATCH] Staging : wlan-ng: fix memcpy with ether_addr

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Date:	Tue,  5 May 2015 16:25:31 +0530
From:	Abhishek Bist <ishubist@...il.com>
To:	gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org, Abhishek Bist <ishubist@...il.com>
Subject: [PATCH] Staging : wlan-ng: fix memcpy with ether_addr_copy in p80211conv.c

This is a patch which fixes memcpy warning found by a checpatch.pl in p80211conv.c
and replaces memcpy with ether_addr_copy.
---
 drivers/staging/wlan-ng/p80211conv.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/wlan-ng/p80211conv.c b/drivers/staging/wlan-ng/p80211conv.c
index bd69e8c..b3f48074 100644
--- a/drivers/staging/wlan-ng/p80211conv.c
+++ b/drivers/staging/wlan-ng/p80211conv.c
@@ -178,21 +178,21 @@ int skb_ether_to_p80211(wlandevice_t *wlandev, u32 ethconv,
 
 	switch (wlandev->macmode) {
 	case WLAN_MACMODE_IBSS_STA:
-		memcpy(p80211_hdr->a3.a1, &e_hdr.daddr, ETH_ALEN);
-		memcpy(p80211_hdr->a3.a2, wlandev->netdev->dev_addr, ETH_ALEN);
-		memcpy(p80211_hdr->a3.a3, wlandev->bssid, ETH_ALEN);
+		ether_addr_copy(p80211_hdr->a3.a1, &e_hdr.daddr);
+		ether_addr_copy(p80211_hdr->a3.a2, wlandev->netdev->dev_addr);
+		ether_addr_copy(p80211_hdr->a3.a3, wlandev->bssid);
 		break;
 	case WLAN_MACMODE_ESS_STA:
 		fc |= cpu_to_le16(WLAN_SET_FC_TODS(1));
-		memcpy(p80211_hdr->a3.a1, wlandev->bssid, ETH_ALEN);
-		memcpy(p80211_hdr->a3.a2, wlandev->netdev->dev_addr, ETH_ALEN);
-		memcpy(p80211_hdr->a3.a3, &e_hdr.daddr, ETH_ALEN);
+		ether_addr_copy(p80211_hdr->a3.a1, wlandev->bssid);
+		ether_addr_copy(p80211_hdr->a3.a2, wlandev->netdev->dev_addr);
+		ether_addr_copy(p80211_hdr->a3.a3, &e_hdr.daddr);
 		break;
 	case WLAN_MACMODE_ESS_AP:
 		fc |= cpu_to_le16(WLAN_SET_FC_FROMDS(1));
-		memcpy(p80211_hdr->a3.a1, &e_hdr.daddr, ETH_ALEN);
-		memcpy(p80211_hdr->a3.a2, wlandev->bssid, ETH_ALEN);
-		memcpy(p80211_hdr->a3.a3, &e_hdr.saddr, ETH_ALEN);
+		ether_addr_copy(p80211_hdr->a3.a1, &e_hdr.daddr);
+		ether_addr_copy(p80211_hdr->a3.a2, wlandev->bssid);
+		ether_addr_copy(p80211_hdr->a3.a3, &e_hdr.saddr);
 		break;
 	default:
 		netdev_err(wlandev->netdev,
@@ -241,7 +241,7 @@ static void orinoco_spy_gather(wlandevice_t *wlandev, char *mac,
 	for (i = 0; i < wlandev->spy_number; i++) {
 
 		if (!memcmp(wlandev->spy_address[i], mac, ETH_ALEN)) {
-			memcpy(wlandev->spy_address[i], mac, ETH_ALEN);
+			ether_addr_copy(wlandev->spy_address[i], mac);
 			wlandev->spy_stat[i].level = rxmeta->signal;
 			wlandev->spy_stat[i].noise = rxmeta->noise;
 			wlandev->spy_stat[i].qual =
-- 
1.8.3.1

How do you "know" it is safe to do this?  Please prove it.




Yes, it is safe to do this because the basic pre-requisite of ether_addr_copy() over memcpy() is that ether_addr_copy() 
is strictly designed to copy an ethernet address where source and destination are a 6 byte array which is true in my case as
p80211_hdr->a3.a1,p80211_hdr->a3.a2,p80211_hdr->a3.a3 are all a six byte array and the next important thing is that they should 
be u16 alligned.So, for that sake i checked it by pahole which clearly shows that the source and destination are u16 byte alligned.And on some architecture ether_addr_copy is faster than memcpy().
	So, it's seems fair enough to use ether_addr_copy() over memcpy() when the size of data to be copied is ETH_ALEN which is 
#define ETH_ALEN 6
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