Currently, the mesh paths associated with a nexthop station are cleaned
up in the following code path:
__sta_info_destroy_part1
synchronize_net()
__sta_info_destroy_part2
-> cleanup_single_sta
-> mesh_sta_cleanup
-> mesh_plink_deactivate
-> mesh_path_flush_by_nexthop
However, there are a couple of problems here:
1) the paths aren't flushed at all if the MPM is running in userspace
(e.g. when using wpa_supplicant or authsae)
2) there is no synchronize_rcu between removing the path and readers
accessing the nexthop, which means the following race is possible:
CPU0 CPU1
~~~~ ~~~~
sta_info_destroy_part1()
synchronize_net()
rcu_read_lock()
mesh_nexthop_resolve()
mpath = mesh_path_lookup()
[...] -> mesh_path_flush_by_nexthop()
sta = rcu_dereference(
mpath->next_hop)
kfree(sta)
access sta <-- CRASH
Fix both of these by unconditionally flushing paths in part1 of sta
destroy. The synchronize_net() will then happen after paths
are flushed, preventing mesh_path_lookup from finding a path with
the to-be-freed nexthop sta.
Also, add a new sta bit and a check in mesh_path_assign_nexthop() to
avoid adding it back between the flush and the synchronize_net().
Fixes this crash:
[ 348.529295] BUG: unable to handle kernel paging request at 00020040
[ 348.530014] IP: [<f929245d>] ieee80211_mps_set_frame_flags+0x40/0xaa
[mac80211]
[ 348.530014] *pde = 00000000
[ 348.530014] Oops: 0000 [#1] PREEMPT
[ 348.530014] Modules linked in: drbg ansi_cprng ctr ccm ppp_generic slhc
ipt_MASQUERADE nf_nat_masquerade_ipv4 8021q ]
[ 348.530014] CPU: 0 PID: 20597 Comm: wget Tainted: G O
4.6.0-rc5-wt=V1 #1
[ 348.530014] Hardware name: To Be Filled By O.E.M./To be filled by O.E.M.,
BIOS 080016 11/07/2014
[ 348.530014] task: f64fa280 ti: f4f9c000 task.ti: f4f9c000
[ 348.530014] EIP: 0060:[<f929245d>] EFLAGS: 00010246 CPU: 0
[ 348.530014] EIP is at ieee80211_mps_set_frame_flags+0x40/0xaa [mac80211]
[ 348.530014] EAX: f4ce63e0 EBX: 00000088 ECX: f3788416 EDX: 00020008
[ 348.530014] ESI: 00000000 EDI: 00000088 EBP: f6409a4c ESP: f6409a40
[ 348.530014] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
[ 348.530014] CR0: 80050033 CR2: 00020040 CR3: 33190000 CR4: 00000690
[ 348.530014] Stack:
[ 348.530014] 00000000 f4ce63e0 f5f9bd80 f6409a64 f9291d80 0000ce67 f5d51e00
f4ce63e0
[ 348.530014] f3788416 f6409a80 f9291dc1 f4ce8320 f4ce63e0 f5d51e00 f4ce63e0
f4ce8320
[ 348.530014] f6409a98 f9277f6f 00000000 00000000 0000007c 00000000 f6409b2c
f9278dd1
[ 348.530014] Call Trace:
[ 348.530014] [<f9291d80>] mesh_nexthop_lookup+0xbb/0xc8 [mac80211]
[ 348.530014] [<f9291dc1>] mesh_nexthop_resolve+0x34/0xd8 [mac80211]
[ 348.530014] [<f9277f6f>] ieee80211_xmit+0x92/0xc1 [mac80211]
[ 348.530014] [<f9278dd1>] __ieee80211_subif_start_xmit+0x807/0x83c [mac80211]
[ 348.530014] [<c04df012>] ? sch_direct_xmit+0xd7/0x1b3
[ 348.530014] [<c022a8c6>] ? __local_bh_enable_ip+0x5d/0x7b
[ 348.530014] [<f956870c>] ? nf_nat_ipv4_out+0x4c/0xd0 [nf_nat_ipv4]
[ 348.530014] [<f957e036>] ? iptable_nat_ipv4_fn+0xf/0xf [iptable_nat]
[ 348.530014] [<c04c6f45>] ? netif_skb_features+0x14d/0x30a
[ 348.530014] [<f9278e10>] ieee80211_subif_start_xmit+0xa/0xe [mac80211]
[ 348.530014] [<c04c769c>] dev_hard_start_xmit+0x1f8/0x267
[ 348.530014] [<c04c7261>] ? validate_xmit_skb.isra.120.part.121+0x10/0x253
[ 348.530014] [<c04defc6>] sch_direct_xmit+0x8b/0x1b3
[ 348.530014] [<c04c7a9c>] __dev_queue_xmit+0x2c8/0x513
[ 348.530014] [<c04c7cfb>] dev_queue_xmit+0xa/0xc
[ 348.530014] [<f91bfc7a>] batadv_send_skb_packet+0xd6/0xec [batman_adv]
[ 348.530014] [<f91bfdc4>] batadv_send_unicast_skb+0x15/0x4a [batman_adv]
[ 348.530014] [<f91b5938>] batadv_dat_send_data+0x27e/0x310 [batman_adv]
[ 348.530014] [<f91c30b5>] ? batadv_tt_global_hash_find.isra.11+0x8/0xa
[batman_adv]
[ 348.530014] [<f91b63f3>] batadv_dat_snoop_outgoing_arp_request+0x208/0x23d
[batman_adv]
[ 348.530014] [<f91c0cd9>] batadv_interface_tx+0x206/0x385 [batman_adv]
[ 348.530014] [<c04c769c>] dev_hard_start_xmit+0x1f8/0x267
[ 348.530014] [<c04c7261>] ? validate_xmit_skb.isra.120.part.121+0x10/0x253
[ 348.530014] [<c04defc6>] sch_direct_xmit+0x8b/0x1b3
[ 348.530014] [<c04c7a9c>] __dev_queue_xmit+0x2c8/0x513
[ 348.530014] [<f80cbd2a>] ? igb_xmit_frame+0x57/0x72 [igb]
[ 348.530014] [<c04c7cfb>] dev_queue_xmit+0xa/0xc
[ 348.530014] [<f843a326>] br_dev_queue_push_xmit+0xeb/0xfb [bridge]
[ 348.530014] [<f843a35f>] br_forward_finish+0x29/0x74 [bridge]
[ 348.530014] [<f843a23b>] ? deliver_clone+0x3b/0x3b [bridge]
[ 348.530014] [<f843a714>] __br_forward+0x89/0xe7 [bridge]
[ 348.530014] [<f843a336>] ? br_dev_queue_push_xmit+0xfb/0xfb [bridge]
[ 348.530014] [<f843a234>] deliver_clone+0x34/0x3b [bridge]
[ 348.530014] [<f843a68b>] ? br_flood+0x95/0x95 [bridge]
[ 348.530014] [<f843a66d>] br_flood+0x77/0x95 [bridge]
[ 348.530014] [<f843a809>] br_flood_forward+0x13/0x1a [bridge]
[ 348.530014] [<f843a68b>] ? br_flood+0x95/0x95 [bridge]
[ 348.530014] [<f843b877>] br_handle_frame_finish+0x392/0x3db [bridge]
[ 348.530014] [<c04e9b2b>] ? nf_iterate+0x2b/0x6b
[ 348.530014] [<f843baa6>] br_handle_frame+0x1e6/0x240 [bridge]
[ 348.530014] [<f843b4e5>] ? br_handle_local_finish+0x6a/0x6a [bridge]
[ 348.530014] [<c04c4ba0>] __netif_receive_skb_core+0x43a/0x66b
[ 348.530014] [<f843b8c0>] ? br_handle_frame_finish+0x3db/0x3db [bridge]
[ 348.530014] [<c023cea4>] ? resched_curr+0x19/0x37
[ 348.530014] [<c0240707>] ? check_preempt_wakeup+0xbf/0xfe
[ 348.530014] [<c0255dec>] ? ktime_get_with_offset+0x5c/0xfc
[ 348.530014] [<c04c4fc1>] __netif_receive_skb+0x47/0x55
[ 348.530014] [<c04c57ba>] netif_receive_skb_internal+0x40/0x5a
[ 348.530014] [<c04c61ef>] napi_gro_receive+0x3a/0x94
[ 348.530014] [<f80ce8d5>] igb_poll+0x6fd/0x9ad [igb]
[ 348.530014] [<c0242bd8>] ? swake_up_locked+0x14/0x26
[ 348.530014] [<c04c5d29>] net_rx_action+0xde/0x250
[ 348.530014] [<c022a743>] __do_softirq+0x8a/0x163
[ 348.530014] [<c022a6b9>] ? __hrtimer_tasklet_trampoline+0x19/0x19
[ 348.530014] [<c021100f>] do_softirq_own_stack+0x26/0x2c
[ 348.530014] <IRQ>
[ 348.530014] [<c022a957>] irq_exit+0x31/0x6f
[ 348.530014] [<c0210eb2>] do_IRQ+0x8d/0xa0
[ 348.530014] [<c058152c>] common_interrupt+0x2c/0x40
[ 348.530014] Code: e7 8c 00 66 81 ff 88 00 75 12 85 d2 75 0e b2 c3 b8 83 e9
29 f9 e8 a7 5f f9 c6 eb 74 66 81 e3 8c 005
[ 348.530014] EIP: [<f929245d>] ieee80211_mps_set_frame_flags+0x40/0xaa
[mac80211] SS:ESP 0068:f6409a40
[ 348.530014] CR2: 0000000000020040
[ 348.530014] ---[ end trace 48556ac26779732e ]---
[ 348.530014] Kernel panic - not syncing: Fatal exception in interrupt
[ 348.530014] Kernel Offset: disabled
Cc: [email protected]
Reported-by: Fred Veldini <[email protected]>
Tested-by: Fred Veldini <[email protected]>
Signed-off-by: Bob Copeland <[email protected]>
---
>From git history, this appears to go back to earliest commits adding
authsae support. I reproduced in a 4.4 kernel, which predates all of
the mesh pathtable rework, though it is harder to hit there than in
the current code.
This is slightly different from the version Fred tested (CCed) --
the version I sent him didn't have the BLOCK_MPATH part, but that
seems necessary to me to prevent re-adding in hwmp_route_info_get().
But I can reproduce the above crash and this patch fixes it for
me.
---
net/mac80211/mesh_pathtbl.c | 4 ++++
net/mac80211/sta_info.c | 10 ++++++++++
net/mac80211/sta_info.h | 2 ++
3 files changed, 16 insertions(+)
diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
index 6db2ddfa0695..798c522b6522 100644
--- a/net/mac80211/mesh_pathtbl.c
+++ b/net/mac80211/mesh_pathtbl.c
@@ -87,6 +87,10 @@ void mesh_path_assign_nexthop(struct mesh_path *mpath,
struct sta_info *sta)
struct ieee80211_hdr *hdr;
unsigned long flags;
+ /* sta is being deleted, don't add back */
+ if (test_sta_flag(sta, WLAN_STA_BLOCK_MPATH))
+ return;
+
rcu_assign_pointer(mpath->next_hop, sta);
spin_lock_irqsave(&mpath->frame_queue.lock, flags);
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 5ccfdbd406bd..f2a1bfa53c04 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -914,6 +914,16 @@ static int __must_check __sta_info_destroy_part1(struct
sta_info *sta)
list_del_rcu(&sta->list);
sta->removed = true;
+ /*
+ * Remove all path table references to the station (and prevent
+ * adding new ones) so that new mesh transmissions won't use it
+ * as a next hop.
+ */
+ if (ieee80211_vif_is_mesh(&sdata->vif)) {
+ set_sta_flag(sta, WLAN_STA_BLOCK_MPATH);
+ mesh_path_flush_by_nexthop(sta);
+ }
+
drv_sta_pre_rcu_remove(local, sta->sdata, sta);
if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN &&
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index c8b8ccc370eb..65ecd3746c3b 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -70,6 +70,7 @@
* @WLAN_STA_MPSP_RECIPIENT: local STA is recipient of a MPSP.
* @WLAN_STA_PS_DELIVER: station woke up, but we're still blocking TX
* until pending frames are delivered
+ * @WLAN_STA_BLOCK_MPATH: block adding this station as a mesh path
*
* @NUM_WLAN_STA_FLAGS: number of defined flags
*/
@@ -100,6 +101,7 @@ enum ieee80211_sta_info_flags {
WLAN_STA_MPSP_OWNER,
WLAN_STA_MPSP_RECIPIENT,
WLAN_STA_PS_DELIVER,
+ WLAN_STA_BLOCK_MPATH,
NUM_WLAN_STA_FLAGS,
};
--
2.6.1
--
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