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* [PATCH wireless-next] net: cfg80211: Validate monitor channel set against radio usage
@ 2026-09-18 17:07 Rory Little
  2026-09-21  9:04 ` Johannes Berg
  2026-09-21 12:04 ` [syzbot ci] " syzbot ci
  0 siblings, 2 replies; 11+ messages in thread
From: Rory Little @ 2026-09-18 17:07 UTC (permalink / raw)
  To: Johannes Berg; +Cc: linux-wireless, Dylan Eskew

Current logic only looks globally at interface counts to validate that a
monitor can have its channel configured. This works to ensure that the
wiphy is not pulled off the channel currently being used by another
active interface, but fails to allow for the case where the channels in
use on the other active interface and the desired channel for the
monitor fall on disjoint sets of radios.

Instead, search for any interface which would cause conflict, otherwise
allowing for the configuration.

Suggested-by: Dylan Eskew <dylan.eskew@candelatech.com>
Signed-off-by: Rory Little <roryl@candelatech.com>
---
 net/wireless/chan.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index 1071e823108b..e417649a543a 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -1810,13 +1810,38 @@ bool cfg80211_reg_check_beaconing(struct wiphy *wiphy,
 }
 EXPORT_SYMBOL(cfg80211_reg_check_beaconing);
 
+static bool cfg80211_can_set_monitor_channel(struct cfg80211_registered_device *rdev,
+					     struct cfg80211_chan_def *chandef)
+{
+	struct wireless_dev *wdev;
+	int radio_idx;
+
+	lockdep_assert_held(&rdev->wiphy.mtx);
+
+	if (cfg80211_has_monitors_only(rdev))
+		return true;
+
+	radio_idx = cfg80211_get_radio_idx_by_chan(&rdev->wiphy, chandef->chan);
+
+	list_for_each_entry(wdev, &rdev->wiphy.wdev_list, list) {
+		if (wdev->iftype == NL80211_IFTYPE_MONITOR)
+			continue;
+		if (!wdev->netdev)
+			continue;
+		if (rdev_get_radio_mask(rdev, wdev->netdev) & BIT(radio_idx))
+			return false;
+	}
+
+	return true;
+}
+
 int cfg80211_set_monitor_channel(struct cfg80211_registered_device *rdev,
 				 struct net_device *dev,
 				 struct cfg80211_chan_def *chandef)
 {
 	if (!rdev->ops->set_monitor_channel)
 		return -EOPNOTSUPP;
-	if (!cfg80211_has_monitors_only(rdev))
+	if (!cfg80211_can_set_monitor_channel(rdev, chandef))
 		return -EBUSY;
 
 	return rdev_set_monitor_channel(rdev, dev, chandef);
-- 
2.52.0


^ permalink raw reply related	[flat|nested] 11+ messages in thread
* [PATCH wireless-next] net: cfg80211: Validate monitor channel set against radio usage
@ 2026-09-17 22:12 Rory Little
  2026-09-20 10:49 ` [syzbot ci] " syzbot ci
  0 siblings, 1 reply; 11+ messages in thread
From: Rory Little @ 2026-09-17 22:12 UTC (permalink / raw)
  To: Johannes Berg; +Cc: linux-wireless, Dylan Eskew

Current logic only looks globally at interface counts to validate that a
monitor can have its channel configured. This works to ensure that the
wiphy is not pulled off the channel currently being used by another
active interface, but fails to allow for the case where the channels in
use on the other active interface and the desired channel for the
monitor fall on disjoint sets of radios.

Instead, search for any interface which would cause conflict, otherwise
allowing for the configuration.

Suggested-by: Dylan Eskew <dylan.eskew@candelatech.com>
Signed-off-by: Rory Little <roryl@candelatech.com>
---
 net/wireless/chan.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/net/wireless/chan.c b/net/wireless/chan.c
index 1071e823108b..e417649a543a 100644
--- a/net/wireless/chan.c
+++ b/net/wireless/chan.c
@@ -1810,13 +1810,38 @@ bool cfg80211_reg_check_beaconing(struct wiphy *wiphy,
 }
 EXPORT_SYMBOL(cfg80211_reg_check_beaconing);
 
+static bool cfg80211_can_set_monitor_channel(struct cfg80211_registered_device *rdev,
+					     struct cfg80211_chan_def *chandef)
+{
+	struct wireless_dev *wdev;
+	int radio_idx;
+
+	lockdep_assert_held(&rdev->wiphy.mtx);
+
+	if (cfg80211_has_monitors_only(rdev))
+		return true;
+
+	radio_idx = cfg80211_get_radio_idx_by_chan(&rdev->wiphy, chandef->chan);
+
+	list_for_each_entry(wdev, &rdev->wiphy.wdev_list, list) {
+		if (wdev->iftype == NL80211_IFTYPE_MONITOR)
+			continue;
+		if (!wdev->netdev)
+			continue;
+		if (rdev_get_radio_mask(rdev, wdev->netdev) & BIT(radio_idx))
+			return false;
+	}
+
+	return true;
+}
+
 int cfg80211_set_monitor_channel(struct cfg80211_registered_device *rdev,
 				 struct net_device *dev,
 				 struct cfg80211_chan_def *chandef)
 {
 	if (!rdev->ops->set_monitor_channel)
 		return -EOPNOTSUPP;
-	if (!cfg80211_has_monitors_only(rdev))
+	if (!cfg80211_can_set_monitor_channel(rdev, chandef))
 		return -EBUSY;
 
 	return rdev_set_monitor_channel(rdev, dev, chandef);
-- 
2.52.0


^ permalink raw reply related	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2026-09-21 21:15 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-09-18 17:07 [PATCH wireless-next] net: cfg80211: Validate monitor channel set against radio usage Rory Little
2026-09-21  9:04 ` Johannes Berg
2026-09-21 18:46   ` [PATCH wireless-next v2] net: cfg80211: validate " Rory Little
2026-09-21 18:59     ` Johannes Berg
2026-09-21 20:17       ` Rory Little
2026-09-21 20:20         ` Johannes Berg
2026-09-21 20:55           ` Rory Little
2026-09-21 21:04     ` [PATCH wireless-next v3] wifi: " Rory Little
2026-09-21 18:46   ` [PATCH wireless-next] net: cfg80211: Validate " Rory Little
2026-09-21 12:04 ` [syzbot ci] " syzbot ci
  -- strict thread matches above, loose matches on Subject: below --
2026-09-17 22:12 [PATCH wireless-next] " Rory Little
2026-09-20 10:49 ` [syzbot ci] " syzbot ci

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