[PATCH RESEND wireless 02/10] wifi: mac80211: reset the AP_VLAN tailroom counter on ifdown

[Johannes Berg <johannes@sipsolutions.net>]

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

On ifup, AP_VLAN interfaces get crypto_tx_tailroom_needed_cnt from
the AP interface, but it's never decremented again unless the AP is
also brought down. Thus, bringing the same AP_VLAN up again will
increment the counter again and eventually hit the sanity check:

  WARN_ON_ONCE(sdata->crypto_tx_tailroom_needed_cnt !=
               master->crypto_tx_tailroom_needed_cnt);

Reset it on ifdown to avoid that.

Assisted-by: LLM
Fixes: f9dca80b98ca ("mac80211: fix AP_VLAN crypto tailroom calculation")
Reported-by: syzbot+de3ee5362db09487ea37@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=de3ee5362db09487ea37
Link: https://patch.msgid.link/20260904170057.1f4fc05e5663.Ic863c2fea0352a9282006378bc9c9dedbe27c037@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 net/mac80211/iface.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index ca66eb493ac7..889c32fd8de1 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -616,6 +616,8 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do
 		RCU_INIT_POINTER(sdata->vif.bss_conf.chanctx_conf, NULL);
 		/* see comment in the default case below */
 		ieee80211_free_keys(sdata, true);
+		/* increased by AP value on ifup, so reset on ifdown */
+		sdata->crypto_tx_tailroom_needed_cnt = 0;
 		/* no need to tell driver */
 		break;
 	case NL80211_IFTYPE_MONITOR:
-- 
2.55.0