Return-path: Received: from mail-lf0-f53.google.com ([209.85.215.53]:34618 "EHLO mail-lf0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750730AbdALO1S (ORCPT ); Thu, 12 Jan 2017 09:27:18 -0500 Received: by mail-lf0-f53.google.com with SMTP id v186so14091000lfa.1 for ; Thu, 12 Jan 2017 06:27:17 -0800 (PST) From: Michal Kazior To: johannes@sipsolutions.net Cc: linux-wireless@vger.kernel.org, greearb@candelatech.com, mohammed@qti.qualcomm.com, Michal Kazior Subject: [PATCH] mac80211: prevent skb/txq mismatch Date: Thu, 12 Jan 2017 15:28:41 +0100 Message-Id: <1484231321-3179-1-git-send-email-michal.kazior@tieto.com> (sfid-20170112_152721_701014_6C9D03BF) Sender: linux-wireless-owner@vger.kernel.org List-ID: Station structure is considered as not uploaded (to driver) until drv_sta_state() finishes. This call is however done after the structure is attached to mac80211 internal lists and hashes. This means mac80211 can lookup (and use) station structure before it is uploaded to a driver. If this happens (structure exists, but sta->uploaded is false) fast_tx path can still be taken. Deep in the fastpath call the sta->uploaded is checked against to derive "pubsta" argument for ieee80211_get_txq(). If sta->uploaded is false (and sta is actually non-NULL) ieee80211_get_txq() effectively downgraded to vif->txq. At first glance this may look innocent but coerces mac80211 into a state that is almost guaranteed (codel may drop offending skb) to crash because a station-oriented skb gets queued up on vif-oriented txq. The ieee80211_tx_dequeue() ends up looking at info->control.flags and tries to use txq->sta which in the fail case is NULL. It's probably pointless to pretend one can downgrade skb from sta-txq to vif-txq. Only drivers using wake_tx_queue were affected. Example crash dump before fix: Unable to handle kernel paging request at virtual address ffffe26c PC is at ieee80211_tx_dequeue+0x204/0x690 [mac80211] [] (ieee80211_tx_dequeue [mac80211]) from [] (ath10k_mac_tx_push_txq+0x54/0x1c0 [ath10k_core]) [] (ath10k_mac_tx_push_txq [ath10k_core]) from [] (ath10k_htt_txrx_compl_task+0xd78/0x11d0 [ath10k_core]) [] (ath10k_htt_txrx_compl_task [ath10k_core]) [] (ath10k_pci_napi_poll+0x54/0xe8 [ath10k_pci]) [] (ath10k_pci_napi_poll [ath10k_pci]) from [] (net_rx_action+0xac/0x160) Reported-by: Mohammed Shafi Shajakhan Signed-off-by: Michal Kazior --- net/mac80211/tx.c | 17 +++++++---------- 1 file changed, 7 insertions(+), 10 deletions(-) diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c index 4dea18be385c..c77fcf83d004 100644 --- a/net/mac80211/tx.c +++ b/net/mac80211/tx.c @@ -1244,13 +1244,16 @@ ieee80211_tx_prepare(struct ieee80211_sub_if_data *sdata, static struct txq_info *ieee80211_get_txq(struct ieee80211_local *local, struct ieee80211_vif *vif, - struct ieee80211_sta *pubsta, + struct sta_info *sta, struct sk_buff *skb) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data; struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); struct ieee80211_txq *txq = NULL; + if (sta && !sta->uploaded) + return NULL; + if ((info->flags & IEEE80211_TX_CTL_SEND_AFTER_DTIM) || (info->control.flags & IEEE80211_TX_CTRL_PS_RESPONSE)) return NULL; @@ -1258,10 +1261,10 @@ static struct txq_info *ieee80211_get_txq(struct ieee80211_local *local, if (!ieee80211_is_data(hdr->frame_control)) return NULL; - if (pubsta) { + if (sta) { u8 tid = skb->priority & IEEE80211_QOS_CTL_TID_MASK; - txq = pubsta->txq[tid]; + txq = sta->sta.txq[tid]; } else if (vif) { txq = vif->txq; } @@ -1504,23 +1507,17 @@ static bool ieee80211_queue_skb(struct ieee80211_local *local, struct fq *fq = &local->fq; struct ieee80211_vif *vif; struct txq_info *txqi; - struct ieee80211_sta *pubsta; if (!local->ops->wake_tx_queue || sdata->vif.type == NL80211_IFTYPE_MONITOR) return false; - if (sta && sta->uploaded) - pubsta = &sta->sta; - else - pubsta = NULL; - if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN) sdata = container_of(sdata->bss, struct ieee80211_sub_if_data, u.ap); vif = &sdata->vif; - txqi = ieee80211_get_txq(local, vif, pubsta, skb); + txqi = ieee80211_get_txq(local, vif, sta, skb); if (!txqi) return false; -- 2.1.4