2021-05-31 20:32:14

by Johannes Berg

Subject: [PATCH v4.9 03/10] mac80211: properly handle A-MSDUs that start with an RFC 1042 header

From: Mathy Vanhoef <[email protected]>

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: [email protected]
Signed-off-by: Mathy Vanhoef <[email protected]>
Link: https://lore.kernel.org/r/20210511200110.0b2b886492f0.I23dd5d685fe16d3b0ec8106e8f01b59f499dffed@changeid
Signed-off-by: Johannes Berg <[email protected]>
---
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