From 1d147bfa64293b2723c4fec50922168658e613ba Mon Sep 17 00:00:00 2001 From: Emmanuel Grumbach Date: Thu, 20 Feb 2014 09:22:11 +0200 Subject: mac80211: fix AP powersave TX vs. wakeup race There is a race between the TX path and the STA wakeup: while a station is sleeping, mac80211 buffers frames until it wakes up, then the frames are transmitted. However, the RX and TX path are concurrent, so the packet indicating wakeup can be processed while a packet is being transmitted. This can lead to a situation where the buffered frames list is emptied on the one side, while a frame is being added on the other side, as the station is still seen as sleeping in the TX path. As a result, the newly added frame will not be send anytime soon. It might be sent much later (and out of order) when the station goes to sleep and wakes up the next time. Additionally, it can lead to the crash below. Fix all this by synchronising both paths with a new lock. Both path are not fastpath since they handle PS situations. In a later patch we'll remove the extra skb queue locks to reduce locking overhead. BUG: unable to handle kernel NULL pointer dereference at 000000b0 IP: [] ieee80211_report_used_skb+0x11/0x3e0 [mac80211] *pde = 00000000 Oops: 0000 [#1] SMP DEBUG_PAGEALLOC EIP: 0060:[] EFLAGS: 00210282 CPU: 1 EIP is at ieee80211_report_used_skb+0x11/0x3e0 [mac80211] EAX: e5900da0 EBX: 00000000 ECX: 00000001 EDX: 00000000 ESI: e41d00c0 EDI: e5900da0 EBP: ebe458e4 ESP: ebe458b0 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 CR0: 8005003b CR2: 000000b0 CR3: 25a78000 CR4: 000407d0 DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 DR6: ffff0ff0 DR7: 00000400 Process iperf (pid: 3934, ti=ebe44000 task=e757c0b0 task.ti=ebe44000) iwlwifi 0000:02:00.0: I iwl_pcie_enqueue_hcmd Sending command LQ_CMD (#4e), seq: 0x0903, 92 bytes at 3[3]:9 Stack: e403b32c ebe458c4 00200002 00200286 e403b338 ebe458cc c10960bb e5900da0 ff76a6ec ebe458d8 00000000 e41d00c0 e5900da0 ebe458f0 ff6f1b75 e403b210 ebe4598c ff723dc1 00000000 ff76a6ec e597c978 e403b758 00000002 00000002 Call Trace: [] ieee80211_free_txskb+0x15/0x20 [mac80211] [] invoke_tx_handlers+0x1661/0x1780 [mac80211] [] ieee80211_tx+0x75/0x100 [mac80211] [] ieee80211_xmit+0x8f/0xc0 [mac80211] [] ieee80211_subif_start_xmit+0x4fe/0xe20 [mac80211] [] dev_hard_start_xmit+0x450/0x950 [] sch_direct_xmit+0xa9/0x250 [] __qdisc_run+0x4b/0x150 [] dev_queue_xmit+0x2c2/0xca0 Cc: stable@vger.kernel.org Reported-by: Yaara Rozenblum Signed-off-by: Emmanuel Grumbach Reviewed-by: Stanislaw Gruszka [reword commit log, use a separate lock] Signed-off-by: Johannes Berg --- net/mac80211/sta_info.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'net/mac80211/sta_info.c') diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c index decd30c1e290..62a5f0889583 100644 --- a/net/mac80211/sta_info.c +++ b/net/mac80211/sta_info.c @@ -330,6 +330,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata, rcu_read_unlock(); spin_lock_init(&sta->lock); + spin_lock_init(&sta->ps_lock); INIT_WORK(&sta->drv_unblock_wk, sta_unblock); INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work); mutex_init(&sta->ampdu_mlme.mtx); @@ -1109,6 +1110,8 @@ void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta) skb_queue_head_init(&pending); + /* sync with ieee80211_tx_h_unicast_ps_buf */ + spin_lock(&sta->ps_lock); /* Send all buffered frames to the station */ for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) { int count = skb_queue_len(&pending), tmp; @@ -1128,6 +1131,7 @@ void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta) } ieee80211_add_pending_skbs_fn(local, &pending, clear_sta_ps_flags, sta); + spin_unlock(&sta->ps_lock); /* This station just woke up and isn't aware of our SMPS state */ if (!ieee80211_smps_is_restrictive(sta->known_smps_mode, -- cgit v1.2.3 From 5108ca828017120981880eeec8a9ec369334a899 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 17 Feb 2014 20:49:03 +0100 Subject: mac80211: insert stations before adding to driver There's a race condition in mac80211 because we add stations to the internal lists after adding them to the driver, which means that (for example) the following can happen: 1. a station connects and is added 2. first, it is added to the driver 3. then, it is added to the mac80211 lists If the station goes to sleep between steps 2 and 3, and the firmware/hardware records it as being asleep, mac80211 will never instruct the driver to wake it up again as it never realized it went to sleep since the RX path discarded the frame as a "spurious class 3 frame", no station entry was present yet. Fix this by adding the station in software first, and only then adding it to the driver. That way, any state that the driver changes will be reflected properly in mac80211's station state. The problematic part is the roll-back if the driver fails to add the station, in that case a bit more is needed. To not make that overly complex prevent starting BA sessions in the meantime. Signed-off-by: Johannes Berg --- net/mac80211/sta_info.c | 30 ++++++++++++++++++++++++------ 1 file changed, 24 insertions(+), 6 deletions(-) (limited to 'net/mac80211/sta_info.c') diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c index 62a5f0889583..ffc1ee6a2ec1 100644 --- a/net/mac80211/sta_info.c +++ b/net/mac80211/sta_info.c @@ -91,7 +91,7 @@ static int sta_info_hash_del(struct ieee80211_local *local, return -ENOENT; } -static void cleanup_single_sta(struct sta_info *sta) +static void __cleanup_single_sta(struct sta_info *sta) { int ac, i; struct tid_ampdu_tx *tid_tx; @@ -139,7 +139,14 @@ static void cleanup_single_sta(struct sta_info *sta) ieee80211_purge_tx_queue(&local->hw, &tid_tx->pending); kfree(tid_tx); } +} +static void cleanup_single_sta(struct sta_info *sta) +{ + struct ieee80211_sub_if_data *sdata = sta->sdata; + struct ieee80211_local *local = sdata->local; + + __cleanup_single_sta(sta); sta_info_free(local, sta); } @@ -488,21 +495,26 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU) goto out_err; } - /* notify driver */ - err = sta_info_insert_drv_state(local, sdata, sta); - if (err) - goto out_err; - local->num_sta++; local->sta_generation++; smp_mb(); + /* simplify things and don't accept BA sessions yet */ + set_sta_flag(sta, WLAN_STA_BLOCK_BA); + /* make the station visible */ sta_info_hash_add(local, sta); list_add_rcu(&sta->list, &local->sta_list); + /* notify driver */ + err = sta_info_insert_drv_state(local, sdata, sta); + if (err) + goto out_remove; + set_sta_flag(sta, WLAN_STA_INSERTED); + /* accept BA sessions now */ + clear_sta_flag(sta, WLAN_STA_BLOCK_BA); ieee80211_recalc_min_chandef(sdata); ieee80211_sta_debugfs_add(sta); @@ -523,6 +535,12 @@ static int sta_info_insert_finish(struct sta_info *sta) __acquires(RCU) mesh_accept_plinks_update(sdata); return 0; + out_remove: + sta_info_hash_del(local, sta); + list_del_rcu(&sta->list); + local->num_sta--; + synchronize_net(); + __cleanup_single_sta(sta); out_err: mutex_unlock(&local->sta_mtx); rcu_read_lock(); -- cgit v1.2.3 From e3685e03b40f5ec7926d9a75bf63467fc4071df9 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Thu, 20 Feb 2014 11:19:58 +0100 Subject: mac80211: fix station wakeup powersave race Consider the following (relatively unlikely) scenario: 1) station goes to sleep while frames are buffered in driver 2) driver blocks wakeup (until no more frames are buffered) 3) station wakes up again 4) driver unblocks wakeup In this case, the current mac80211 code will do the following: 1) WLAN_STA_PS_STA set 2) WLAN_STA_PS_DRIVER set 3) - nothing - 4) WLAN_STA_PS_DRIVER cleared As a result, no frames will be delivered to the client, even though it is awake, until it sends another frame to us that triggers ieee80211_sta_ps_deliver_wakeup() in sta_ps_end(). Since we now take the PS spinlock, we can fix this while at the same time removing the complexity with the pending skb queue function. This was broken since my commit 50a9432daeec ("mac80211: fix powersaving clients races") due to removing the clearing of WLAN_STA_PS_STA in the RX path. While at it, fix a cleanup path issue when a station is removed while the driver is still blocking its wakeup. Signed-off-by: Johannes Berg --- net/mac80211/sta_info.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-) (limited to 'net/mac80211/sta_info.c') diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c index ffc1ee6a2ec1..a023b432143b 100644 --- a/net/mac80211/sta_info.c +++ b/net/mac80211/sta_info.c @@ -99,7 +99,8 @@ static void __cleanup_single_sta(struct sta_info *sta) struct ieee80211_local *local = sdata->local; struct ps_data *ps; - if (test_sta_flag(sta, WLAN_STA_PS_STA)) { + if (test_sta_flag(sta, WLAN_STA_PS_STA) || + test_sta_flag(sta, WLAN_STA_PS_DRIVER)) { if (sta->sdata->vif.type == NL80211_IFTYPE_AP || sta->sdata->vif.type == NL80211_IFTYPE_AP_VLAN) ps = &sdata->bss->ps; @@ -109,6 +110,7 @@ static void __cleanup_single_sta(struct sta_info *sta) return; clear_sta_flag(sta, WLAN_STA_PS_STA); + clear_sta_flag(sta, WLAN_STA_PS_DRIVER); atomic_dec(&ps->num_sta_ps); sta_info_recalc_tim(sta); @@ -1090,10 +1092,14 @@ struct ieee80211_sta *ieee80211_find_sta(struct ieee80211_vif *vif, } EXPORT_SYMBOL(ieee80211_find_sta); -static void clear_sta_ps_flags(void *_sta) +/* powersave support code */ +void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta) { - struct sta_info *sta = _sta; struct ieee80211_sub_if_data *sdata = sta->sdata; + struct ieee80211_local *local = sdata->local; + struct sk_buff_head pending; + int filtered = 0, buffered = 0, ac; + unsigned long flags; struct ps_data *ps; if (sdata->vif.type == NL80211_IFTYPE_AP || @@ -1104,20 +1110,6 @@ static void clear_sta_ps_flags(void *_sta) else return; - clear_sta_flag(sta, WLAN_STA_PS_DRIVER); - if (test_and_clear_sta_flag(sta, WLAN_STA_PS_STA)) - atomic_dec(&ps->num_sta_ps); -} - -/* powersave support code */ -void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta) -{ - struct ieee80211_sub_if_data *sdata = sta->sdata; - struct ieee80211_local *local = sdata->local; - struct sk_buff_head pending; - int filtered = 0, buffered = 0, ac; - unsigned long flags; - clear_sta_flag(sta, WLAN_STA_SP); BUILD_BUG_ON(BITS_TO_LONGS(IEEE80211_NUM_TIDS) > 1); @@ -1148,9 +1140,13 @@ void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta) buffered += tmp - count; } - ieee80211_add_pending_skbs_fn(local, &pending, clear_sta_ps_flags, sta); + ieee80211_add_pending_skbs(local, &pending); + clear_sta_flag(sta, WLAN_STA_PS_DRIVER); + clear_sta_flag(sta, WLAN_STA_PS_STA); spin_unlock(&sta->ps_lock); + atomic_dec(&ps->num_sta_ps); + /* This station just woke up and isn't aware of our SMPS state */ if (!ieee80211_smps_is_restrictive(sta->known_smps_mode, sdata->smps_mode) && -- cgit v1.2.3