[PATCH 4.9 20/43] mac80211: drop data frames without key on encrypted links

Sasha Levin
2021-08-24T17:36:58Z

From: Johannes Berg <johannes.berg@intel.com>

commit a0761a301746ec2d92d7fcb82af69c0a6a4339aa upstream.

If we know that we have an encrypted link (based on having had
a key configured for TX in the past) then drop all data frames
in the key selection handler if there's no key anymore.

This fixes an issue with mac80211 internal TXQs - there we can
buffer frames for an encrypted link, but then if the key is no
longer there when they're dequeued, the frames are sent without
encryption. This happens if a station is disconnected while the
frames are still on the TXQ.

Detecting that a link should be encrypted based on a first key
having been configured for TX is fine as there are no use cases
for a connection going from with encryption to no encryption.
With extended key IDs, however, there is a case of having a key
configured for only decryption, so we can't just trigger this
behaviour on a key being configured.

Cc: stable@vger.kernel.org
Reported-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200326150855.6865c7f28a14.I9fb1d911b064262d33e33dfba730cdeef83926ca@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[pali: Backported to 4.19 and older versions]
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/mac80211/debugfs_sta.c | 1 +
net/mac80211/key.c | 1 +
net/mac80211/sta_info.h | 1 +
net/mac80211/tx.c | 12 +++++++++---
4 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index 14ec63a02669..91b94ac9a88a 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -80,6 +80,7 @@ static const char * const sta_flag_names[] = {
FLAG(MPSP_OWNER),
FLAG(MPSP_RECIPIENT),
FLAG(PS_DELIVER),
+ FLAG(USES_ENCRYPTION),
#undef FLAG
};

diff --git a/net/mac80211/key.c b/net/mac80211/key.c
index 4e23f240f599..a0d9507cb6a7 100644
--- a/net/mac80211/key.c
+++ b/net/mac80211/key.c
@@ -334,6 +334,7 @@ static void ieee80211_key_replace(struct ieee80211_sub_if_data *sdata,
if (sta) {
if (pairwise) {
rcu_assign_pointer(sta->ptk[idx], new);
+ set_sta_flag(sta, WLAN_STA_USES_ENCRYPTION);
sta->ptk_idx = idx;
ieee80211_check_fast_xmit(sta);
} else {
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index fd31c4db1282..0909332965bc 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -100,6 +100,7 @@ enum ieee80211_sta_info_flags {
WLAN_STA_MPSP_OWNER,
WLAN_STA_MPSP_RECIPIENT,
WLAN_STA_PS_DELIVER,
+ WLAN_STA_USES_ENCRYPTION,

NUM_WLAN_STA_FLAGS,
};
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index eebbddccb47b..48d0dd0beaa5 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -588,10 +588,13 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;

- if (unlikely(info->flags & IEEE80211_TX_INTFL_DONT_ENCRYPT))
+ if (unlikely(info->flags & IEEE80211_TX_INTFL_DONT_ENCRYPT)) {
tx->key = NULL;
- else if (tx->sta &&
- (key = rcu_dereference(tx->sta->ptk[tx->sta->ptk_idx])))
+ return TX_CONTINUE;
+ }
+
+ if (tx->sta &&
+ (key = rcu_dereference(tx->sta->ptk[tx->sta->ptk_idx])))
tx->key = key;
else if (ieee80211_is_group_privacy_action(tx->skb) &&
(key = rcu_dereference(tx->sdata->default_multicast_key)))
@@ -652,6 +655,9 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
if (!skip_hw && tx->key &&
tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
info->control.hw_key = &tx->key->conf;
+ } else if (!ieee80211_is_mgmt(hdr->frame_control) && tx->sta &&
+ test_sta_flag(tx->sta, WLAN_STA_USES_ENCRYPTION)) {
+ return TX_DROP;
}

return TX_CONTINUE;
--
2.30.2