Messages in this thread | | | Date | Fri, 1 Sep 2023 18:59:44 +0800 | Subject | Re: [PATCH] ath9k: fix null-ptr-deref in ath_chanctx_event | From | Dongliang Mu <> |
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On 2023/9/1 18:41, 'Toke Høiland-Jørgensen' via HUST OS Kernel Contribution wrote: > Dongliang Mu <dzm91@hust.edu.cn> writes: > >> Smatch reports: >> >> ath_chanctx_event() error: we previously assumed 'vif' could be null >> >> The function ath_chanctx_event can be called with vif argument as NULL. >> If vif is NULL, ath_dbg can trigger a null pointer dereference. >> >> Fix this by adding a null pointer check. >> >> Fixes: 878066e745b5 ("ath9k: Add more debug statements for channel context") >> Signed-off-by: Dongliang Mu <dzm91@hust.edu.cn> >> --- >> drivers/net/wireless/ath/ath9k/channel.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/net/wireless/ath/ath9k/channel.c b/drivers/net/wireless/ath/ath9k/channel.c >> index 571062f2e82a..e343c8962d14 100644 >> --- a/drivers/net/wireless/ath/ath9k/channel.c >> +++ b/drivers/net/wireless/ath/ath9k/channel.c >> @@ -576,7 +576,9 @@ void ath_chanctx_event(struct ath_softc *sc, struct ieee80211_vif *vif, >> if (sc->sched.state != ATH_CHANCTX_STATE_WAIT_FOR_BEACON) >> break; >> >> - ath_dbg(common, CHAN_CTX, "Preparing beacon for vif: %pM\n", vif->addr); >> + if (vif) >> + ath_dbg(common, CHAN_CTX, >> + "Preparing beacon for vif: %pM\n", vif->addr); > Please don't send patches for static checker errors without actually > checking if there is a valid bug. Which there isn't in this case.
Before sending this patch, I searched in the code, there are many call sites of ath_chanctx_event with argument vif as NULL.
Functions calling this function: ath_chanctx_event
File Function Line 0 beacon.c ath9k_beacon_tasklet 459 ath_chanctx_event(sc, vif, ATH_CHANCTX_EVENT_BEACON_PREPARE); 1 channel.c ath_chanctx_check_active 321 ath_chanctx_event(sc, NULL, 2 channel.c ath_chanctx_beacon_sent_ev 781 ath_chanctx_event(sc, NULL, ev); 3 channel.c ath_chanctx_beacon_recv_ev 787 ath_chanctx_event(sc, NULL, ev); 4 channel.c ath_chanctx_timer 1054 ath_chanctx_event(sc, NULL, ATH_CHANCTX_EVENT_TSF_TIMER); 5 channel.c ath_chanctx_set_next 1321 ath_chanctx_event(sc, NULL, ATH_CHANCTX_EVENT_SWITCH); 6 channel.c ath9k_p2p_ps_timer 1566 ath_chanctx_event(sc, NULL, ATH_CHANCTX_EVENT_TSF_TIMER); 7 main.c ath9k_sta_state 1671 ath_chanctx_event(sc, vif, 8 main.c ath9k_remove_chanctx 2577 ath_chanctx_event(sc, NULL, ATH_CHANCTX_EVENT_UNASSIGN); 9 xmit.c ath_tx_edma_tasklet 2749 ath_chanctx_event(sc, NULL,
This NULL parameters would cause some abnormal behaviors.
> Specifically, that branch of the switch statement dereferences the avp > pointer, which will be NULL if 'vif' is. Meaning we will have crashed > way before reaching this statement if vif is indeed NULL. Yeah, you are right. However, no matter where or which variable causing the null-ptr-def crash, the crash is there.
I think this is unexpected.
Let me know if I make any mistakes
> > -Toke >
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