This patch is based on a BUG as reported by Bongani Hlope at https://lore.kernel.org/all/20260502125824.425d7159@bongani-mini.home.org.za/ When a channel-switch announcement (CSA) beacon is received, cfg80211 queues a wiphy work item that eventually calls mt7921_channel_switch_rx_beacon(). If the station disconnects (or the channel context is otherwise torn down) between the time the work is queued and the time it runs, the driver's dev->new_ctx pointer can already have been cleared to NULL. mt7921_channel_switch_rx_beacon() then dereferences new_ctx unconditionally, triggering a NULL pointer dereference at address 0x0: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:mt7921_channel_switch_rx_beacon+0x1f/0x100 [mt7921_common] The same missing guard exists in mt7925_channel_switch_rx_beacon(), which shares the same code pattern introduced by the same commit. Add an early-return NULL check for dev->new_ctx in both mt7921_channel_switch_rx_beacon() and mt7925_channel_switch_rx_beacon(). When new_ctx is NULL there is no pending channel switch to process, so returning immediately is the correct and safe action. Fixes: 8aa2f59260eb ("wifi: mt76: mt7921: introduce CSA support") Reported-by: Bongani Hlope Oops-Analysis: http://oops.fenrus.org/reports/lkml/20260502125824.425d7159@bongani-mini.home.org.za/report.html Link: https://lore.kernel.org/all/20260502125824.425d7159@bongani-mini.home.org.za/ Signed-off-by: Arjan van de Ven Cc: linux-wireless@vger.kernel.org Cc: linux-mediatek@lists.infradead.org Cc: Felix Fietkau Cc: Lorenzo Bianconi Cc: Ryder Lee --- drivers/net/wireless/mediatek/mt76/mt7921/main.c | 3 +++ drivers/net/wireless/mediatek/mt76/mt7925/main.c | 3 +++ 2 files changed, 6 insertions(+) --- a/drivers/net/wireless/mediatek/mt76/mt7921/main.c +++ b/drivers/net/wireless/mediatek/mt76/mt7921/main.c @@ -1503,6 +1503,9 @@ static void mt7921_channel_switch_rx_beacon(struct ieee80211_hw *hw, struct mt792x_dev *dev = mt792x_hw_dev(hw); struct mt792x_vif *mvif = (struct mt792x_vif *)vif->drv_priv; u16 beacon_interval = vif->bss_conf.beacon_int; + + if (!dev->new_ctx) + return; if (cfg80211_chandef_identical(&chsw->chandef, &dev->new_ctx->def) && --- a/drivers/net/wireless/mediatek/mt76/mt7925/main.c +++ b/drivers/net/wireless/mediatek/mt76/mt7925/main.c @@ -2392,6 +2392,9 @@ static void mt7925_channel_switch_rx_beacon(struct ieee80211_hw *hw, u16 beacon_interval; if (ieee80211_vif_is_mld(vif)) return; + + if (!dev->new_ctx) + return; beacon_interval = vif->bss_conf.beacon_int;