The brcmf_btcoex_detach() only shuts down the btcoex timer, if the flag timer_on is false. However, the brcmf_btcoex_timerfunc(), which runs as timer handler, sets timer_on to false. This creates a critical race condition: 1.If brcmf_btcoex_detach() is called while brcmf_btcoex_timerfunc() is executing, it may observe timer_on as false and skip the call to timer_shutdown_sync(). 2.The brcmf_btcoex_timerfunc() may then reschedule the brcmf_btcoex_info worker after the cancel_work_sync() has been executed. 3.Subsequently, the brcmf_btcoex_info structure is freed. 4.Finally, the rescheduled worker attempts to execute, leading to use-after-free bugs by accessing the freed brcmf_btcoex_info object. The following diagram illustrates this sequence of events: cpu0 cpu1 brcmf_btcoex_detach | brcmf_btcoex_timerfunc | bt_local->timer_on = false; if (cfg->btcoex->timer_on) | ... | cancel_work_sync(); | ... | schedule_work() //reschedule kfree(cfg->btcoex);//free | | brcmf_btcoex_handler() //worker | btci-> //use To resolve this race condition, drop the conditional check and call timer_shutdown_sync() directly. It can deactivate the timer reliably, regardless of its current state. Once stopped, the timer_on state is then set to false. Fixes: 61730d4dfffc ("brcmfmac: support critical protocol API for DHCP") Signed-off-by: Duoming Zhou --- drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c index 69ef8cf203d2..67c0c5a92f99 100644 --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/btcoex.c @@ -393,10 +393,8 @@ void brcmf_btcoex_detach(struct brcmf_cfg80211_info *cfg) if (!cfg->btcoex) return; - if (cfg->btcoex->timer_on) { - cfg->btcoex->timer_on = false; - timer_shutdown_sync(&cfg->btcoex->timer); - } + timer_shutdown_sync(&cfg->btcoex->timer); + cfg->btcoex->timer_on = false; cancel_work_sync(&cfg->btcoex->work); -- 2.34.1