From a1d5ff5651ea592c67054233b14b30bf4452999c Mon Sep 17 00:00:00 2001
From: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Date: Tue, 11 May 2021 20:02:44 +0200
Subject: [PATCH] mac80211: properly handle A-MSDUs that start with an RFC 1042 header
Git-commit: a1d5ff5651ea592c67054233b14b30bf4452999c
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git
Patch-mainline: Queued in subsystem maintainer repo
References: CVE-2020-24587 CVE-2020-24586 bsc#1185863 bsc#1185862 bsc#1185859

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 include/net/cfg80211.h |    5 +++--
 net/mac80211/rx.c      |    2 +-
 net/wireless/util.c    |    5 +++--
 3 files changed, 7 insertions(+), 5 deletions(-)

--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -4601,7 +4601,7 @@ unsigned int ieee80211_get_mesh_hdrlen(s
  */
 int ieee80211_data_to_8023_exthdr(struct sk_buff *skb, struct ethhdr *ehdr,
 				  const u8 *addr, enum nl80211_iftype iftype,
-				  u8 data_offset);
+				  u8 data_offset, bool is_amsdu);
 
 /**
  * ieee80211_data_to_8023 - convert an 802.11 data frame to 802.3
@@ -4613,7 +4613,7 @@ int ieee80211_data_to_8023_exthdr(struct
 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, 0);
+	return ieee80211_data_to_8023_exthdr(skb, NULL, addr, iftype, 0, false);
 }
 
 /**
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -2557,7 +2557,7 @@ __ieee80211_rx_h_amsdu(struct ieee80211_
 	if (ieee80211_data_to_8023_exthdr(skb, &ethhdr,
 					  rx->sdata->vif.addr,
 					  rx->sdata->vif.type,
-					  data_offset))
+					  data_offset, true))
 		return RX_DROP_UNUSABLE;
 
 	ieee80211_amsdu_to_8023s(skb, &frame_list, dev->dev_addr,
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -421,7 +421,7 @@ 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,
-				  u8 data_offset)
+				  u8 data_offset, bool is_amsdu)
 {
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 	struct {
@@ -509,7 +510,7 @@ int ieee80211_data_to_8023_exthdr(struct
 	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)))