[PATCH 6/8] wifi: mac80211: validate S1G TWT params before driver setup

[Zhao Li]

A received S1G TWT setup frame is length-checked in
ieee80211_process_rx_twt_action() before it is queued: it requires

  skb->len >= IEEE80211_MIN_ACTION_SIZE + sizeof(twt_setup) + 2

and then skb->len >= IEEE80211_MIN_ACTION_SIZE + 3 + twt->length, where
twt->length is attacker-controlled. twt->length can be as small as 3
(the control byte plus the 2-byte req_type) and the frame still passes,
so only those bytes are guaranteed present.

For an individual (non-broadcast) agreement, ieee80211_s1g_rx_twt_setup()
calls drv_add_twt_setup(), and both trace_drv_add_twt_setup() and the
driver ->add_twt_setup() callback read the full struct
ieee80211_twt_params via twt->params (req_type, twt, min_twt_dur,
mantissa, channel). That needs twt->length >= sizeof(twt->control) +
sizeof(struct ieee80211_twt_params) = 15, so with the minimal 3-byte
element they read up to 12 bytes past the end of the frame.

The broadcast path only rejects the agreement and touches req_type,
which is always present, so it is unaffected. For the individual path,
require twt->length to cover the control byte plus a full
ieee80211_twt_params block before calling drv_add_twt_setup(), and drop
the frame otherwise.

Fixes: f5a4c24e689f ("mac80211: introduce individual TWT support in AP mode")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: Codex:gpt-5
Assisted-by: Claude:opus-4.8
Signed-off-by: Zhao Li <enderaoelyther@xxxxxxxxx>
---
 net/mac80211/s1g.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/mac80211/s1g.c b/net/mac80211/s1g.c
index 5af4a0c6c6424..abc338e22e59c 100644
--- a/net/mac80211/s1g.c
+++ b/net/mac80211/s1g.c
@@ -101,6 +101,10 @@ ieee80211_s1g_rx_twt_setup(struct ieee80211_sub_if_data *sdata,
 	struct ieee80211_twt_setup *twt = (void *)mgmt->u.action.s1g.variable;
 	struct ieee80211_twt_params *twt_agrt = (void *)twt->params;
 
+	if (!(twt->control & IEEE80211_TWT_CONTROL_NEG_TYPE_BROADCAST) &&
+	    twt->length < sizeof(twt->control) + sizeof(*twt_agrt))
+		return;
+
 	twt_agrt->req_type &= cpu_to_le16(~IEEE80211_TWT_REQTYPE_REQUEST);
 
 	/* broadcast TWT not supported yet */
-- 
2.50.1 (Apple Git-155)