package: fix segfault of iwinfo.scanlist("radio0").

This is a bug revealed in r41830.

First, the static variable `char nif[IFNAMSIZ]` of nl80211_phy2ifname()
would be zeroed out if the argument is "wlan0" or the like.  This will
happen in the following call stack.

 nl80211_get_scanlist("radio0", buf, len);
   nl80211_phy2ifname("radio0")			// return static var nif with content "wlan0"
   nl80211_get_scanlist(nif, buf, len);		// tail call
     nl80211_get_mode(nif);
        nl80211_phy2ifname(nif);		// zero out nif

Later we try nl80211_ifadd("") which was supposed to create interface
"tmp.", but that won't happen because nl80211_msg() will put an invalid
ifidx 0 to the nlmsg.

Then iwinfo_ifup() and iwinfo_ifdown() would fail and happily
nl80211_get_scanlist() returned 0 and left *len undefined.

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

SVN-Revision: 42151

package/network/utils/iwinfo/src/iwinfo_lua.c

@@ -362,7 +362,7 @@ static int iwinfo_L_txpwrlist(lua_State *L, int (*func)(const char *, char *, in
 /* Wrapper for scan list */
 static int iwinfo_L_scanlist(lua_State *L, int (*func)(const char *, char *, int *))
 {
-	int i, x, len;
+	int i, x, len = 0;
 	char rv[IWINFO_BUFSIZE];
 	char macstr[18];
 	const char *ifname = luaL_checkstring(L, 1);

package/network/utils/iwinfo/src/iwinfo_nl80211.c

@@ -215,6 +215,9 @@ static struct nl80211_msg_conveyor * nl80211_msg(const char *ifname,
 	int ifidx = -1, phyidx = -1;
 	struct nl80211_msg_conveyor *cv;
 
+	if (ifname == NULL)
+		return NULL;
+
 	if (nl80211_init() < 0)
 		return NULL;
 
@@ -227,7 +230,8 @@ static struct nl80211_msg_conveyor * nl80211_msg(const char *ifname,
 	else
 		ifidx = if_nametoindex(ifname);
 
-	if ((ifidx < 0) && (phyidx < 0))
+	/* Valid ifidx must be greater than 0 */
+	if ((ifidx <= 0) && (phyidx < 0))
 		return NULL;
 
 	cv = nl80211_new(nls->nl80211, cmd, flags);
@@ -500,12 +504,15 @@ static char * nl80211_phy2ifname(const char *ifname)
 	DIR *d;
 	struct dirent *e;
 
+	/* Only accept phy name of the form phy%d or radio%d */
 	if (!ifname)
 		return NULL;
 	else if (!strncmp(ifname, "phy", 3))
 		phyidx = atoi(&ifname[3]);
 	else if (!strncmp(ifname, "radio", 5))
 		phyidx = atoi(&ifname[5]);
+	else
+		return NULL;
 
 	memset(nif, 0, sizeof(nif));