cfg80211: add helper to find an IE that matches a byte-array

There are a few places where an IE that matches not only the EID, but
also other bytes inside the element, needs to be found.  To simplify
that and reduce the amount of similar code, implement a new helper
function to match the EID and an extra array of bytes.

Additionally, simplify cfg80211_find_vendor_ie() by using the new
match function.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 27 insertions, 31 deletions

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 0358e12be54b..b5bd58d0f731 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -352,52 +352,48 @@ void cfg80211_bss_expire(struct cfg80211_registered_device *rdev)
 	__cfg80211_bss_expire(rdev, jiffies - IEEE80211_SCAN_RESULT_EXPIRE);
 }
 
-const u8 *cfg80211_find_ie(u8 eid, const u8 *ies, int len)
+const u8 *cfg80211_find_ie_match(u8 eid, const u8 *ies, int len,
+				 const u8 *match, int match_len,
+				 int match_offset)
 {
-	while (len > 2 && ies[0] != eid) {
+	/* match_offset can't be smaller than 2, unless match_len is
+	 * zero, in which case match_offset must be zero as well.
+	 */
+	if (WARN_ON((match_len && match_offset < 2) ||
+		    (!match_len && match_offset)))
+		return NULL;
+
+	while (len >= 2 && len >= ies[1] + 2) {
+		if ((ies[0] == eid) &&
+		    (ies[1] + 2 >= match_offset + match_len) &&
+		    !memcmp(ies + match_offset, match, match_len))
+			return ies;
+
 		len -= ies[1] + 2;
 		ies += ies[1] + 2;
 	}
-	if (len < 2)
-		return NULL;
-	if (len < 2 + ies[1])
-		return NULL;
-	return ies;
+
+	return NULL;
 }
-EXPORT_SYMBOL(cfg80211_find_ie);
+EXPORT_SYMBOL(cfg80211_find_ie_match);
 
 const u8 *cfg80211_find_vendor_ie(unsigned int oui, int oui_type,
 				  const u8 *ies, int len)
 {
-	struct ieee80211_vendor_ie *ie;
-	const u8 *pos = ies, *end = ies + len;
-	int ie_oui;
+	const u8 *ie;
+	u8 match[] = { oui >> 16, oui >> 8, oui, oui_type };
+	int match_len = (oui_type < 0) ? 3 : sizeof(match);
 
 	if (WARN_ON(oui_type > 0xff))
 		return NULL;
 
-	while (pos < end) {
-		pos = cfg80211_find_ie(WLAN_EID_VENDOR_SPECIFIC, pos,
-				       end - pos);
-		if (!pos)
-			return NULL;
-
-		ie = (struct ieee80211_vendor_ie *)pos;
-
-		/* make sure we can access ie->len */
-		BUILD_BUG_ON(offsetof(struct ieee80211_vendor_ie, len) != 1);
+	ie = cfg80211_find_ie_match(WLAN_EID_VENDOR_SPECIFIC, ies, len,
+				    match, match_len, 2);
 
-		if (ie->len < sizeof(*ie))
-			goto cont;
+	if (ie && (ie[1] < 4))
+		return NULL;
 
-		ie_oui = ie->oui[0] << 16 | ie->oui[1] << 8 | ie->oui[2];
-		if (ie_oui == oui &&
-		    (oui_type < 0 || ie->oui_type == oui_type))
-			return pos;
-cont:
-		pos += 2 + ie->len;
-	}
-	return NULL;
+	return ie;
 }
 EXPORT_SYMBOL(cfg80211_find_vendor_ie);