wifi: mac80211: don't allow injecting frames wider than the chanctx

Frames injected on a monitor interface can carry a radiotap
field requesting a bandwidth, which mac80211 passes down to
the driver regardless of the the actual operational bandwidth.

If the bandwidth requested is too wide, that triggers a warning
in hwsim:

  WARN_ON(hwsim_get_chanwidth(bw) > hwsim_get_chanwidth(confbw))

Drop such frames entirely instead since they cannot be sent.

Assisted-by: LLM
Fixes: 646e76bb5daf ("mac80211: parse VHT info in injected frames")
Reported-by: syzbot+435fdb053cf98bfa5778@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=435fdb053cf98bfa5778
Link: https://patch.msgid.link/20260908122838.201719-13-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

3 files changed, 31 insertions, 4 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 9d1fac6e8082..ed6a5874ff96 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -7638,11 +7638,14 @@ bool ieee80211_tx_prepare_skb(struct ieee80211_hw *hw,
  *
  * @skb: packet injected by userspace
  * @dev: the &struct device of this 802.11 device
+ * @chandef: the channel definition the frame will be transmitted on, or
+ *	%NULL to skip the bandwidth checks
  *
  * Return: %true if the radiotap header was parsed, %false otherwise
  */
 bool ieee80211_parse_tx_radiotap(struct sk_buff *skb,
-				 struct net_device *dev);
+				 struct net_device *dev,
+				 const struct cfg80211_chan_def *chandef);
 
 /**
  * struct ieee80211_noa_data - holds temporary data for tracking P2P NoA state
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 842bfb4a7cb6..ca66eb493ac7 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -991,7 +991,7 @@ static u16 ieee80211_monitor_select_queue(struct net_device *dev,
 	/* reset flags and info before parsing radiotap header */
 	memset(info, 0, sizeof(*info));
 
-	if (!ieee80211_parse_tx_radiotap(skb, dev))
+	if (!ieee80211_parse_tx_radiotap(skb, dev, NULL))
 		return 0; /* doesn't matter, frame will be dropped */
 
 	len_rthdr = ieee80211_get_radiotap_len(skb->data);
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index d155fb319a55..c343ed56506a 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2105,8 +2105,29 @@ static bool ieee80211_validate_radiotap_len(struct sk_buff *skb)
 	return true;
 }
 
+static bool ieee80211_rate_bw_usable(u16 rate_flags,
+				     const struct cfg80211_chan_def *chandef)
+{
+	int width;
+
+	if (!chandef)
+		return true;
+
+	if (rate_flags & IEEE80211_TX_RC_160_MHZ_WIDTH)
+		width = 160;
+	else if (rate_flags & IEEE80211_TX_RC_80_MHZ_WIDTH)
+		width = 80;
+	else if (rate_flags & IEEE80211_TX_RC_40_MHZ_WIDTH)
+		width = 40;
+	else
+		return true;
+
+	return width <= cfg80211_chandef_get_width(chandef);
+}
+
 bool ieee80211_parse_tx_radiotap(struct sk_buff *skb,
-				 struct net_device *dev)
+				 struct net_device *dev,
+				 const struct cfg80211_chan_def *chandef)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct ieee80211_radiotap_iterator iterator;
@@ -2280,6 +2301,9 @@ bool ieee80211_parse_tx_radiotap(struct sk_buff *skb,
 		struct ieee80211_supported_band *sband =
 			local->hw.wiphy->bands[info->band];
 
+		if (!ieee80211_rate_bw_usable(rate_flags, chandef))
+			return false;
+
 		info->control.flags |= IEEE80211_TX_CTRL_RATE_INJECT;
 
 		for (i = 0; i < IEEE80211_TX_MAX_RATES; i++) {
@@ -2479,7 +2503,7 @@ netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb,
 	 * selected chandef above to accurately set injection rates and
 	 * retransmissions.
 	 */
-	if (!ieee80211_parse_tx_radiotap(skb, dev))
+	if (!ieee80211_parse_tx_radiotap(skb, dev, chandef))
 		goto fail_rcu;
 
 	/* remove the injection radiotap header */