mt76_put_vif_phy_link() frees the offchannel mlink with plain kfree() after rcu_assign_pointer(NULL). However, rcu_assign_pointer only prevents future RCU readers from obtaining the pointer -- it does not wait for existing readers that already hold it via rcu_dereference. The TX datapath (e.g. mt7996_mac_write_txwi) dereferences mlink->wcid and mlink->idx under rcu_read_lock. If a TX softirq obtained the pointer via rcu_dereference just before the NULL assignment, it will dereference freed memory after the kfree. struct mt76_vif_link already contains an rcu_head field that is unused at this free site -- a developer oversight, since the adjacent kfree_rcu_mightsleep call for rx_sc in the same function shows the pattern was understood. Replace kfree(mlink) with kfree_rcu(mlink, rcu_head). Fixes: a8f424c1287c ("wifi: mt76: add multi-radio remain_on_channel functions") Signed-off-by: Rajat Gupta --- drivers/net/wireless/mediatek/mt76/channel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/wireless/mediatek/mt76/channel.c b/drivers/net/wireless/mediatek/mt76/channel.c index 05eee6470..6edcb3b8f 100644 --- a/drivers/net/wireless/mediatek/mt76/channel.c +++ b/drivers/net/wireless/mediatek/mt76/channel.c @@ -307,7 +307,7 @@ void mt76_put_vif_phy_link(struct mt76_phy *phy, struct ieee80211_vif *vif, rcu_assign_pointer(mvif->offchannel_link, NULL); dev->drv->vif_link_remove(phy, vif, &vif->bss_conf, mlink); - kfree(mlink); + kfree_rcu(mlink, rcu_head); } void mt76_roc_complete(struct mt76_phy *phy) -- 2.43.0