Return-path: Received: from mail2.candelatech.com ([208.74.158.173]:47740 "EHLO mail2.candelatech.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932203AbcHSNej (ORCPT ); Fri, 19 Aug 2016 09:34:39 -0400 Message-ID: <57B70AED.2010200@candelatech.com> (sfid-20160819_153446_739844_BFCBC91A) Date: Fri, 19 Aug 2016 06:34:37 -0700 From: Ben Greear MIME-Version: 1.0 To: Michal Kazior CC: "ath10k@lists.infradead.org" , linux-wireless Subject: Re: [PATCH 1/3] ath10k: Ensure there are no stale ar->txqs entries. References: <1471569995-10028-1-git-send-email-greearb@candelatech.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-wireless-owner@vger.kernel.org List-ID: On 08/18/2016 11:59 PM, Michal Kazior wrote: > On 19 August 2016 at 03:26, wrote: >> From: Ben Greear >> >> I was seeing kernel crashes due to accessing freed memory >> while debugging a 9984 firmware that was crashing often. >> >> This patch fixes the crashes. I am not certain if there >> is a better way or not. >> >> Signed-off-by: Ben Greear >> --- >> drivers/net/wireless/ath/ath10k/mac.c | 10 ++++++++++ >> 1 file changed, 10 insertions(+) >> >> diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c >> index 5659ef1..916119c 100644 >> --- a/drivers/net/wireless/ath/ath10k/mac.c >> +++ b/drivers/net/wireless/ath/ath10k/mac.c >> @@ -4172,8 +4172,10 @@ static void ath10k_mac_txq_init(struct ieee80211_txq *txq) >> static void ath10k_mac_txq_unref(struct ath10k *ar, struct ieee80211_txq *txq) >> { >> struct ath10k_txq *artxq = (void *)txq->drv_priv; >> + struct ath10k_txq *tmp, *walker; >> struct ath10k_skb_cb *cb; >> struct sk_buff *msdu; >> + struct ieee80211_txq *txq_tmp; >> int msdu_id; >> >> if (!txq) >> @@ -4182,6 +4184,14 @@ static void ath10k_mac_txq_unref(struct ath10k *ar, struct ieee80211_txq *txq) >> spin_lock_bh(&ar->txqs_lock); >> if (!list_empty(&artxq->list)) >> list_del_init(&artxq->list); >> + >> + /* Remove from ar->txqs in case it still exists there. */ >> + list_for_each_entry_safe(walker, tmp, &ar->txqs, list) { >> + txq_tmp = container_of((void *)walker, struct ieee80211_txq, >> + drv_priv); >> + if (txq_tmp == txq) >> + list_del(&walker->list); >> + } > > How could this even happen? All artxq->list accesses (add/del) are > protected by txqs_lock so this shouldn't happen, no? > > Do you perhaps have the logic around txqs reworked in your tree? I don't have any significant changes as far as I can tell. I can build you a buggy 9984 firmware to reproduce the problem if you want... Maybe the upstream patch could WARN_ON in this case to see if anyone else ever hits it? I did see a comment in the mac80211 about some assumptions on the driver with regard to station teardown...I am not 100% sure ath10k meets that assumption, so maybe that is why I could see this problem. Thanks, Ben -- Ben Greear Candela Technologies Inc http://www.candelatech.com