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From:   Johannes Berg <johannes@sipsolutions.net>
To:     linux-wireless@vger.kernel.org
Cc:     stable@vger.kernel.org, Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Subject: [PATCH v4.9 03/10] mac80211: properly handle A-MSDUs that start with an RFC 1042 header
Date:   Mon, 31 May 2021 22:30:14 +0200
Message-Id: <20210531203021.180010-4-johannes@sipsolutions.net>
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From: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>

commit a1d5ff5651ea592c67054233b14b30bf4452999c upstream.

Properly parse A-MSDUs whose first 6 bytes happen to equal a rfc1042
header. This can occur in practice when the destination MAC address
equals AA:AA:03:00:00:00. More importantly, this simplifies the next
patch to mitigate A-MSDU injection attacks.

Cc: stable@vger.kernel.org
Signed-off-by: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Link: https://lore.kernel.org/r/20210511200110.0b2b886492f0.I23dd5d685fe16d3b0ec8106e8f01b59f499dffed@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 include/net/cfg80211.h | 5 +++--
 net/mac80211/rx.c      | 3 ++-
 net/wireless/util.c    | 5 +++--
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 28a0d7a8c142..ba388549b38c 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -4056,7 +4056,8 @@ unsigned int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr);
  * Return: 0 on success. Non-zero on error.
  */
 int ieee80211_data_to_8023_exthdr(struct sk_buff *skb, struct ethhdr *ehdr,
-				  const u8 *addr, enum nl80211_iftype iftype);
+				  const u8 *addr, enum nl80211_iftype iftype,
+				  bool is_amsdu);
 
 /**
  * ieee80211_data_to_8023 - convert an 802.11 data frame to 802.3
@@ -4068,7 +4069,7 @@ int ieee80211_data_to_8023_exthdr(struct sk_buff *skb, struct ethhdr *ehdr,
 static inline int ieee80211_data_to_8023(struct sk_buff *skb, const u8 *addr,
 					 enum nl80211_iftype iftype)
 {
-	return ieee80211_data_to_8023_exthdr(skb, NULL, addr, iftype);
+	return ieee80211_data_to_8023_exthdr(skb, NULL, addr, iftype, false);
 }
 
 /**
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index d3aee2859f0a..6c54941a3265 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2428,7 +2428,8 @@ ieee80211_rx_h_amsdu(struct ieee80211_rx_data *rx)
 
 	if (ieee80211_data_to_8023_exthdr(skb, &ethhdr,
 					  rx->sdata->vif.addr,
-					  rx->sdata->vif.type))
+					  rx->sdata->vif.type,
+					  true))
 		return RX_DROP_UNUSABLE;
 
 	ieee80211_amsdu_to_8023s(skb, &frame_list, dev->dev_addr,
diff --git a/net/wireless/util.c b/net/wireless/util.c
index 262922cf6a0c..8c67b7cf1def 100644
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -421,7 +421,8 @@ unsigned int ieee80211_get_mesh_hdrlen(struct ieee80211s_hdr *meshhdr)
 EXPORT_SYMBOL(ieee80211_get_mesh_hdrlen);
 
 int ieee80211_data_to_8023_exthdr(struct sk_buff *skb, struct ethhdr *ehdr,
-				  const u8 *addr, enum nl80211_iftype iftype)
+				  const u8 *addr, enum nl80211_iftype iftype,
+				  bool is_amsdu)
 {
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 	struct {
@@ -509,7 +510,7 @@ int ieee80211_data_to_8023_exthdr(struct sk_buff *skb, struct ethhdr *ehdr,
 	skb_copy_bits(skb, hdrlen, &payload, sizeof(payload));
 	tmp.h_proto = payload.proto;
 
-	if (likely((ether_addr_equal(payload.hdr, rfc1042_header) &&
+	if (likely((!is_amsdu && ether_addr_equal(payload.hdr, rfc1042_header) &&
 		    tmp.h_proto != htons(ETH_P_AARP) &&
 		    tmp.h_proto != htons(ETH_P_IPX)) ||
 		   ether_addr_equal(payload.hdr, bridge_tunnel_header)))
-- 
2.31.1