[PATCH 3.2 022/106] mac80211: strictly check mesh address extension mode

[Ben Hutchings]

3.2.93-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx>

commit 5667c86acf021e6dcf02584408b4484a273ac68f upstream.

Mesh forwarding path checks for address extension mode to fetch
appropriate proxied address and MPP address. Existing condition
that looks for 6 address format is not strict enough so that
frames with improper values are processed and invalid entries
are added into MPP table. Fix that by adding a stricter check before
processing the packet.

Per IEEE Std 802.11s-2011 spec. Table 7-6g1 lists address extension
mode 0x3 as reserved one. And also Table Table 9-13 does not specify
0x3 as valid address field.

Fixes: 9b395bc3be1c ("mac80211: verify that skb data is present")
Signed-off-by: Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
[bwh: Backported to 3.2: add mesh_flags variable in ieee80211_data_to_8023(),
 added separately upstream]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/mac80211/rx.c   |  3 ++-
 net/wireless/util.c | 10 ++++++----
 2 files changed, 8 insertions(+), 5 deletions(-)

--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1959,7 +1959,8 @@ ieee80211_rx_h_mesh_fwding(struct ieee80
 		if (is_multicast_ether_addr(hdr->addr1)) {
 			mpp_addr = hdr->addr3;
 			proxied_addr = mesh_hdr->eaddr1;
-		} else if (mesh_hdr->flags & MESH_FLAGS_AE_A5_A6) {
+		} else if ((mesh_hdr->flags & MESH_FLAGS_AE) ==
+			    MESH_FLAGS_AE_A5_A6) {
 			/* has_a4 already checked in ieee80211_rx_mesh_check */
 			mpp_addr = hdr->addr4;
 			proxied_addr = mesh_hdr->eaddr2;
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -360,12 +360,15 @@ int ieee80211_data_to_8023(struct sk_buf
 		if (iftype == NL80211_IFTYPE_MESH_POINT) {
 			struct ieee80211s_hdr *meshdr =
 				(struct ieee80211s_hdr *) (skb->data + hdrlen);
+			u8 mesh_flags;
+
 			/* make sure meshdr->flags is on the linear part */
 			if (!pskb_may_pull(skb, hdrlen + 1))
 				return -1;
-			if (meshdr->flags & MESH_FLAGS_AE_A4)
+			mesh_flags = meshdr->flags & MESH_FLAGS_AE;
+			if (mesh_flags == MESH_FLAGS_AE_A4)
 				return -1;
-			if (meshdr->flags & MESH_FLAGS_AE_A5_A6) {
+			if (mesh_flags == MESH_FLAGS_AE_A5_A6) {
 				skb_copy_bits(skb, hdrlen +
 					offsetof(struct ieee80211s_hdr, eaddr1),
 				       	dst, ETH_ALEN);
@@ -386,12 +389,15 @@ int ieee80211_data_to_8023(struct sk_buf
 		if (iftype == NL80211_IFTYPE_MESH_POINT) {
 			struct ieee80211s_hdr *meshdr =
 				(struct ieee80211s_hdr *) (skb->data + hdrlen);
+			u8 mesh_flags;
+
 			/* make sure meshdr->flags is on the linear part */
 			if (!pskb_may_pull(skb, hdrlen + 1))
 				return -1;
-			if (meshdr->flags & MESH_FLAGS_AE_A5_A6)
+			mesh_flags = meshdr->flags & MESH_FLAGS_AE;
+			if (mesh_flags == MESH_FLAGS_AE_A5_A6)
 				return -1;
-			if (meshdr->flags & MESH_FLAGS_AE_A4)
+			if (mesh_flags == MESH_FLAGS_AE_A4)
 				skb_copy_bits(skb, hdrlen +
 					offsetof(struct ieee80211s_hdr, eaddr1),
 					src, ETH_ALEN);