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It then calls ieee80211_free_txskb() before dropping the lock. ieee80211_free_txskb() is not just a passive SKB release. For SKBs with TX status state it can report a dropped frame through cfg80211/nl80211, and that path can reach netlink tap transmit. This is the same reason the pending queue cleanup in ieee80211_do_stop() already unlinks SKBs under the queue lock and frees them after IRQ state is restored. The buggy scenario involves two paths, with each column showing the order within that path: AP_VLAN management TX: AP_VLAN stop: 1. attach ACK-status state 1. clear the running state 2. queue a multicast SKB on 2. take ps->bc_buf.lock with IRQs parent ps->bc_buf disabled 3. unlink the AP_VLAN SKB 4. call ieee80211_free_txskb() Unlink matching AP_VLAN SKBs from ps->bc_buf under the existing lock, but move them to a local free queue. Drop the lock and restore IRQ state before calling ieee80211_free_txskb(). WARNING: kernel/softirq.c:430 at __local_bh_enable_ip Fixes: 397a7a24ef8c ("mac80211: free ps->bc_buf skbs on vlan device stop") Assisted-by: Codex:gpt-5.5 Signed-off-by: Cen Zhang --- net/mac80211/iface.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c index 086272c3ec08..43460a705a6b 100644 --- a/net/mac80211/iface.c +++ b/net/mac80211/iface.c @@ -588,6 +588,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do WARN_ON(!list_empty(&sdata->u.ap.vlans)); } else if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN) { /* remove all packets in parent bc_buf pointing to this dev */ + __skb_queue_head_init(&freeq); ps = &sdata->bss->ps; spin_lock_irqsave(&ps->bc_buf.lock, flags); @@ -595,10 +596,15 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do if (skb->dev == sdata->dev) { __skb_unlink(skb, &ps->bc_buf); local->total_ps_buffered--; - ieee80211_free_txskb(&local->hw, skb); + __skb_queue_tail(&freeq, skb); } } spin_unlock_irqrestore(&ps->bc_buf.lock, flags); + + skb_queue_walk_safe(&freeq, skb, tmp) { + __skb_unlink(skb, &freeq); + ieee80211_free_txskb(&local->hw, skb); + } } if (going_down) -- 2.43.0