[PATCH 5.10/5.15 v2] wifi: mac80211: mesh: release the channel if start fails

[Alexander Martyniuk <alexevgmart@gmail.com>]

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

commit ae97fff6495a8764bc0ef281cfe5444f701e527f upstream.

ieee80211_join_mesh() acquires a channel context and then calls
ieee80211_start_mesh(), which can fail. In that case, the chanctx
isn't released then interface removal will attempt to unassign it
after it's removed from the driver, hitting:

  wlan0: Failed check-sdata-in-driver check, flags: 0x0
  WARNING: net/mac80211/driver-ops.c:366 at drv_unassign_vif_chanctx
   ieee80211_assign_link_chanctx
   __ieee80211_link_release_channel
   ieee80211_link_release_channel
   ieee80211_teardown_sdata
   unregister_netdevice_many_notify
   _cfg80211_unregister_wdev
   ieee80211_remove_interfaces
   ieee80211_unregister_hw
   mac80211_hwsim_del_radio
   hwsim_exit_net

Correctly release the channel on start failures.

Assisted-by: LLM
Reported-by: syzbot+63a84ea9c0f57d6133fa@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=63a84ea9c0f57d6133fa
Fixes: 2b5e19677592 ("mac80211: cache mesh beacon")
Link: https://patch.msgid.link/20260908122838.201719-21-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
[Alexander: No such function ieee80211_link_release_channel(), so
ieee80211_vif_release_channel() is used]
Signed-off-by: Alexander Martyniuk <alexevgmart@gmail.com>
---
Backport fix for CVE-2026-98326
 net/mac80211/cfg.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 29bcb5f6013a..d5865f4083cf 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2311,7 +2311,14 @@ static int ieee80211_join_mesh(struct wiphy *wiphy, struct net_device *dev,
 	if (err)
 		return err;
 
-	return ieee80211_start_mesh(sdata);
+	err = ieee80211_start_mesh(sdata);
+	if (err) {
+		mutex_lock(&sdata->local->mtx);
+		ieee80211_vif_release_channel(sdata);
+		mutex_unlock(&sdata->local->mtx);
+	}
+
+	return err;
 }
 
 static int ieee80211_leave_mesh(struct wiphy *wiphy, struct net_device *dev)
-- 
2.43.0