| Message ID | 1463332756-31423-1-git-send-email-me@bobcopeland.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Johannes Berg |
| Headers | show |
On Sun, 2016-05-15 at 13:19 -0400, Bob Copeland wrote: > 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 before destroying > the sta, and by adding a synchronize_net() after path flush to ensure > no active readers can still dereference the sta. > [...] Applied, thanks for the fix and the detailed description! johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c index 4c6404e1ad6e..21b1fdf5d01d 100644 --- a/net/mac80211/mesh.c +++ b/net/mac80211/mesh.c @@ -161,6 +161,10 @@ void mesh_sta_cleanup(struct sta_info *sta) del_timer_sync(&sta->mesh->plink_timer); } + /* make sure no readers can access nexthop sta from here on */ + mesh_path_flush_by_nexthop(sta); + synchronize_net(); + if (changed) ieee80211_mbss_info_change_notify(sdata, changed); }
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 before destroying the sta, and by adding a synchronize_net() after path flush to ensure no active readers can still dereference the sta. 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: stable@vger.kernel.org Reported-by: Fred Veldini <fred.veldini@gmail.com> Tested-by: Fred Veldini <fred.veldini@gmail.com> Signed-off-by: Bob Copeland <me@bobcopeland.com> --- v1: "mac80211: mesh: flush paths early in sta destroy" v2: Dropped block_mpath bit, just do this in part2 so that sta_info_get is guaranteed not to return the to-be-deleted sta, and add a second synchronize_rcu to wait for concurrent readers. Changed title. net/mac80211/mesh.c | 4 ++++ 1 file changed, 4 insertions(+)