[Bionic][PATCH 2/2] mac80211: handle deauthentication/disassociation from TDLS peer

[Wen-chien Jesse Sung]

From: Yu Wang <yyuwang at codeaurora.org>

BugLink: https://launchpad.net/bugs/1839105

When receiving a deauthentication/disassociation frame from a TDLS
peer, a station should not disconnect the current AP, but only
disable the current TDLS link if it's enabled.

Without this change, a TDLS issue can be reproduced by following the
steps as below:

1. STA-1 and STA-2 are connected to AP, bidirection traffic is running
   between STA-1 and STA-2.
2. Set up TDLS link between STA-1 and STA-2, stay for a while, then
   teardown TDLS link.
3. Repeat step #2 and monitor the connection between STA and AP.

During the test, one STA may send a deauthentication/disassociation
frame to another, after TDLS teardown, with reason code 6/7, which
means: Class 2/3 frame received from nonassociated STA.

On receive this frame, the receiver STA will disconnect the current
AP and then reconnect. It's not a expected behavior, purpose of this
frame should be disabling the TDLS link, not the link with AP.

Cc: stable at vger.kernel.org
Signed-off-by: Yu Wang <yyuwang at codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg at intel.com>

CVE-2019-0136

(cherry picked from commit 79c92ca42b5a3e0ea172ea2ce8df8e125af237da)
Signed-off-by: Wen-chien Jesse Sung <jesse.sung at canonical.com>
---
 net/mac80211/ieee80211_i.h |  3 +++
 net/mac80211/mlme.c        | 12 +++++++++++-
 net/mac80211/tdls.c        | 23 +++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 61db1fb156ed..7c5fc2b24567 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -2153,6 +2153,9 @@ void ieee80211_tdls_cancel_channel_switch(struct wiphy *wiphy,
 					  const u8 *addr);
 void ieee80211_teardown_tdls_peers(struct ieee80211_sub_if_data *sdata);
 void ieee80211_tdls_chsw_work(struct work_struct *wk);
+void ieee80211_tdls_handle_disconnect(struct ieee80211_sub_if_data *sdata,
+				      const u8 *peer, u16 reason);
+const char *ieee80211_get_reason_code_string(u16 reason_code);
 
 extern const struct ethtool_ops ieee80211_ethtool_ops;
 
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index d20a84b9d1a8..42a33b79fa2f 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2733,7 +2733,7 @@ static void ieee80211_rx_mgmt_auth(struct ieee80211_sub_if_data *sdata,
 #define case_WLAN(type) \
 	case WLAN_REASON_##type: return #type
 
-static const char *ieee80211_get_reason_code_string(u16 reason_code)
+const char *ieee80211_get_reason_code_string(u16 reason_code)
 {
 	switch (reason_code) {
 	case_WLAN(UNSPECIFIED);
@@ -2798,6 +2798,11 @@ static void ieee80211_rx_mgmt_deauth(struct ieee80211_sub_if_data *sdata,
 	if (len < 24 + 2)
 		return;
 
+	if (!ether_addr_equal(mgmt->bssid, mgmt->sa)) {
+		ieee80211_tdls_handle_disconnect(sdata, mgmt->sa, reason_code);
+		return;
+	}
+
 	if (ifmgd->associated &&
 	    ether_addr_equal(mgmt->bssid, ifmgd->associated->bssid)) {
 		const u8 *bssid = ifmgd->associated->bssid;
@@ -2847,6 +2852,11 @@ static void ieee80211_rx_mgmt_disassoc(struct ieee80211_sub_if_data *sdata,
 
 	reason_code = le16_to_cpu(mgmt->u.disassoc.reason_code);
 
+	if (!ether_addr_equal(mgmt->bssid, mgmt->sa)) {
+		ieee80211_tdls_handle_disconnect(sdata, mgmt->sa, reason_code);
+		return;
+	}
+
 	sdata_info(sdata, "disassociated from %pM (Reason: %u=%s)\n",
 		   mgmt->sa, reason_code,
 		   ieee80211_get_reason_code_string(reason_code));
diff --git a/net/mac80211/tdls.c b/net/mac80211/tdls.c
index 6e7aa65cf345..7a32b6820397 100644
--- a/net/mac80211/tdls.c
+++ b/net/mac80211/tdls.c
@@ -1988,3 +1988,26 @@ void ieee80211_tdls_chsw_work(struct work_struct *wk)
 	}
 	rtnl_unlock();
 }
+
+void ieee80211_tdls_handle_disconnect(struct ieee80211_sub_if_data *sdata,
+				      const u8 *peer, u16 reason)
+{
+	struct ieee80211_sta *sta;
+
+	rcu_read_lock();
+	sta = ieee80211_find_sta(&sdata->vif, peer);
+	if (!sta || !sta->tdls) {
+		rcu_read_unlock();
+		return;
+	}
+	rcu_read_unlock();
+
+	tdls_dbg(sdata, "disconnected from TDLS peer %pM (Reason: %u=%s)\n",
+		 peer, reason,
+		 ieee80211_get_reason_code_string(reason));
+
+	ieee80211_tdls_oper_request(&sdata->vif, peer,
+				    NL80211_TDLS_TEARDOWN,
+				    WLAN_REASON_TDLS_TEARDOWN_UNREACHABLE,
+				    GFP_ATOMIC);
+}
-- 
2.20.1