From d5ad6ab61cbd89afdb60881f6274f74328af3ee9 Mon Sep 17 00:00:00 2001 From: Felix Fietkau Date: Sat, 14 Mar 2026 06:54:55 +0000 Subject: [PATCH] wifi: mac80211: always free skb on ieee80211_tx_prepare_skb() failure ieee80211_tx_prepare_skb() has three error paths, but only two of them free the skb. The first error path (ieee80211_tx_prepare() returning TX_DROP) does not free it, while invoke_tx_handlers() failure and the fragmentation check both do. Add kfree_skb() to the first error path so all three are consistent, and remove the now-redundant frees in callers (ath9k, mt76, mac80211_hwsim) to avoid double-free. Document the skb ownership guarantee in the function's kdoc. Signed-off-by: Felix Fietkau Link: https://patch.msgid.link/20260314065455.2462900-1-nbd@nbd.name Fixes: 06be6b149f7e ("mac80211: add ieee80211_tx_prepare_skb() helper function") Signed-off-by: Johannes Berg --- drivers/net/wireless/ath/ath9k/channel.c | 6 ++---- drivers/net/wireless/mediatek/mt76/scan.c | 4 +--- drivers/net/wireless/virtual/mac80211_hwsim.c | 1 - include/net/mac80211.h | 4 +++- net/mac80211/tx.c | 4 +++- 5 files changed, 9 insertions(+), 10 deletions(-) diff --git a/drivers/net/wireless/ath/ath9k/channel.c b/drivers/net/wireless/ath/ath9k/channel.c index 121e51ce1bc0..8b27d8cc086a 100644 --- a/drivers/net/wireless/ath/ath9k/channel.c +++ b/drivers/net/wireless/ath/ath9k/channel.c @@ -1006,7 +1006,7 @@ static void ath_scan_send_probe(struct ath_softc *sc, skb_set_queue_mapping(skb, IEEE80211_AC_VO); if (!ieee80211_tx_prepare_skb(sc->hw, vif, skb, band, NULL)) - goto error; + return; txctl.txq = sc->tx.txq_map[IEEE80211_AC_VO]; if (ath_tx_start(sc->hw, skb, &txctl)) @@ -1119,10 +1119,8 @@ ath_chanctx_send_vif_ps_frame(struct ath_softc *sc, struct ath_vif *avp, skb->priority = 7; skb_set_queue_mapping(skb, IEEE80211_AC_VO); - if (!ieee80211_tx_prepare_skb(sc->hw, vif, skb, band, &sta)) { - dev_kfree_skb_any(skb); + if (!ieee80211_tx_prepare_skb(sc->hw, vif, skb, band, &sta)) return false; - } break; default: return false; diff --git a/drivers/net/wireless/mediatek/mt76/scan.c b/drivers/net/wireless/mediatek/mt76/scan.c index ff9176cdee3d..63b0447e55c1 100644 --- a/drivers/net/wireless/mediatek/mt76/scan.c +++ b/drivers/net/wireless/mediatek/mt76/scan.c @@ -63,10 +63,8 @@ mt76_scan_send_probe(struct mt76_dev *dev, struct cfg80211_ssid *ssid) rcu_read_lock(); - if (!ieee80211_tx_prepare_skb(phy->hw, vif, skb, band, NULL)) { - ieee80211_free_txskb(phy->hw, skb); + if (!ieee80211_tx_prepare_skb(phy->hw, vif, skb, band, NULL)) goto out; - } info = IEEE80211_SKB_CB(skb); if (req->no_cck) diff --git a/drivers/net/wireless/virtual/mac80211_hwsim.c b/drivers/net/wireless/virtual/mac80211_hwsim.c index f6b890dea7e0..1b6e55eb81a2 100644 --- a/drivers/net/wireless/virtual/mac80211_hwsim.c +++ b/drivers/net/wireless/virtual/mac80211_hwsim.c @@ -3021,7 +3021,6 @@ static void hw_scan_work(struct work_struct *work) hwsim->tmp_chan->band, NULL)) { rcu_read_unlock(); - kfree_skb(probe); continue; } diff --git a/include/net/mac80211.h b/include/net/mac80211.h index 7f9d96939a4e..adce2144a678 100644 --- a/include/net/mac80211.h +++ b/include/net/mac80211.h @@ -7407,7 +7407,9 @@ void ieee80211_report_wowlan_wakeup(struct ieee80211_vif *vif, * @band: the band to transmit on * @sta: optional pointer to get the station to send the frame to * - * Return: %true if the skb was prepared, %false otherwise + * Return: %true if the skb was prepared, %false otherwise. + * On failure, the skb is freed by this function; callers must not + * free it again. * * Note: must be called under RCU lock */ diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 8cdbd417d7be..b7aedaab8483 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -1899,8 +1899,10 @@ bool ieee80211_tx_prepare_skb(struct ieee80211_hw *hw, struct ieee80211_tx_data tx; struct sk_buff *skb2; - if (ieee80211_tx_prepare(sdata, &tx, NULL, skb) == TX_DROP) + if (ieee80211_tx_prepare(sdata, &tx, NULL, skb) == TX_DROP) { + kfree_skb(skb); return false; + } info->band = band; info->control.vif = vif;