[PATCH 6.6 130/166] wifi: mac80211: always free skb on ieee80211_tx_prepare_skb() failure

Greg Kroah-Hartman
2026-04-24T13:39:02Z

From: Felix Fietkau <nbd@nbd.name>

[ Upstream commit d5ad6ab61cbd89afdb60881f6274f74328af3ee9 ]

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 <nbd@nbd.name>
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 <johannes.berg@intel.com>
[ Exclude changes to drivers/net/wireless/mediatek/mt76/scan.c as this file is first
introduced by commit 31083e38548f("wifi: mt76: add code for emulating hardware scanning")
after linux-6.14.]
Signed-off-by: Li hongliang <1468888505@139.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/ath/ath9k/channel.c | 6 ++----
drivers/net/wireless/virtual/mac80211_hwsim.c | 1 -
include/net/mac80211.h | 4 ++++
net/mac80211/tx.c | 4 +++-
4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/channel.c b/drivers/net/wireless/ath/ath9k/channel.c
index 571062f2e82a7..ba8ec5112afe8 100644
--- a/drivers/net/wireless/ath/ath9k/channel.c
+++ b/drivers/net/wireless/ath/ath9k/channel.c
@@ -1011,7 +1011,7 @@ 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))
@@ -1124,10 +1124,8 @@ 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/virtual/mac80211_hwsim.c b/drivers/net/wireless/virtual/mac80211_hwsim.c
index 1214e7dcc8124..bf12ff0ab06ab 100644
--- a/drivers/net/wireless/virtual/mac80211_hwsim.c
+++ b/drivers/net/wireless/virtual/mac80211_hwsim.c
@@ -2892,7 +2892,6 @@ 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 adaa1b2323d2c..85d785060e761 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -7032,6 +7032,10 @@ 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.
+ * On failure, the skb is freed by this function; callers must not
+ * free it again.
+ *
* Note: must be called under RCU lock
*/
bool ieee80211_tx_prepare_skb(struct ieee80211_hw *hw,
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 7eddcb6f96455..2a708132320c4 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1911,8 +1911,10 @@ 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;
--
2.53.0