package/kernel/mac80211/patches/303-mac80211-mesh-flush-mesh-paths-unconditionally.patch

   1 From: Bob Copeland <me@bobcopeland.com>
   2 Date: Sun, 15 May 2016 13:19:16 -0400
   3 Subject: [PATCH] mac80211: mesh: flush mesh paths unconditionally
   4
   5 Currently, the mesh paths associated with a nexthop station are cleaned
   6 up in the following code path:
   7
   8     __sta_info_destroy_part1
   9     synchronize_net()
  10     __sta_info_destroy_part2
  11      -> cleanup_single_sta
  12        -> mesh_sta_cleanup
  13          -> mesh_plink_deactivate
  14            -> mesh_path_flush_by_nexthop
  15
  16 However, there are a couple of problems here:
  17
  18 1) the paths aren't flushed at all if the MPM is running in userspace
  19    (e.g. when using wpa_supplicant or authsae)
  20
  21 2) there is no synchronize_rcu between removing the path and readers
  22    accessing the nexthop, which means the following race is possible:
  23
  24 CPU0                            CPU1
  25 ~~~~                            ~~~~
  26                                 sta_info_destroy_part1()
  27                                 synchronize_net()
  28 rcu_read_lock()
  29 mesh_nexthop_resolve()
  30   mpath = mesh_path_lookup()
  31                                 [...] -> mesh_path_flush_by_nexthop()
  32   sta = rcu_dereference(
  33     mpath->next_hop)
  34                                 kfree(sta)
  35   access sta <-- CRASH
  36
  37 Fix both of these by unconditionally flushing paths before destroying
  38 the sta, and by adding a synchronize_net() after path flush to ensure
  39 no active readers can still dereference the sta.
  40
  41 Fixes this crash:
  42
  43 [  348.529295] BUG: unable to handle kernel paging request at 00020040
  44 [  348.530014] IP: [<f929245d>] ieee80211_mps_set_frame_flags+0x40/0xaa [mac80211]
  45 [  348.530014] *pde = 00000000
  46 [  348.530014] Oops: 0000 [#1] PREEMPT
  47 [  348.530014] Modules linked in: drbg ansi_cprng ctr ccm ppp_generic slhc ipt_MASQUERADE nf_nat_masquerade_ipv4 8021q ]
  48 [  348.530014] CPU: 0 PID: 20597 Comm: wget Tainted: G           O 4.6.0-rc5-wt=V1 #1
  49 [  348.530014] Hardware name: To Be Filled By O.E.M./To be filled by O.E.M., BIOS 080016  11/07/2014
  50 [  348.530014] task: f64fa280 ti: f4f9c000 task.ti: f4f9c000
  51 [  348.530014] EIP: 0060:[<f929245d>] EFLAGS: 00010246 CPU: 0
  52 [  348.530014] EIP is at ieee80211_mps_set_frame_flags+0x40/0xaa [mac80211]
  53 [  348.530014] EAX: f4ce63e0 EBX: 00000088 ECX: f3788416 EDX: 00020008
  54 [  348.530014] ESI: 00000000 EDI: 00000088 EBP: f6409a4c ESP: f6409a40
  55 [  348.530014]  DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
  56 [  348.530014] CR0: 80050033 CR2: 00020040 CR3: 33190000 CR4: 00000690
  57 [  348.530014] Stack:
  58 [  348.530014]  00000000 f4ce63e0 f5f9bd80 f6409a64 f9291d80 0000ce67 f5d51e00 f4ce63e0
  59 [  348.530014]  f3788416 f6409a80 f9291dc1 f4ce8320 f4ce63e0 f5d51e00 f4ce63e0 f4ce8320
  60 [  348.530014]  f6409a98 f9277f6f 00000000 00000000 0000007c 00000000 f6409b2c f9278dd1
  61 [  348.530014] Call Trace:
  62 [  348.530014]  [<f9291d80>] mesh_nexthop_lookup+0xbb/0xc8 [mac80211]
  63 [  348.530014]  [<f9291dc1>] mesh_nexthop_resolve+0x34/0xd8 [mac80211]
  64 [  348.530014]  [<f9277f6f>] ieee80211_xmit+0x92/0xc1 [mac80211]
  65 [  348.530014]  [<f9278dd1>] __ieee80211_subif_start_xmit+0x807/0x83c [mac80211]
  66 [  348.530014]  [<c04df012>] ? sch_direct_xmit+0xd7/0x1b3
  67 [  348.530014]  [<c022a8c6>] ? __local_bh_enable_ip+0x5d/0x7b
  68 [  348.530014]  [<f956870c>] ? nf_nat_ipv4_out+0x4c/0xd0 [nf_nat_ipv4]
  69 [  348.530014]  [<f957e036>] ? iptable_nat_ipv4_fn+0xf/0xf [iptable_nat]
  70 [  348.530014]  [<c04c6f45>] ? netif_skb_features+0x14d/0x30a
  71 [  348.530014]  [<f9278e10>] ieee80211_subif_start_xmit+0xa/0xe [mac80211]
  72 [  348.530014]  [<c04c769c>] dev_hard_start_xmit+0x1f8/0x267
  73 [  348.530014]  [<c04c7261>] ?  validate_xmit_skb.isra.120.part.121+0x10/0x253
  74 [  348.530014]  [<c04defc6>] sch_direct_xmit+0x8b/0x1b3
  75 [  348.530014]  [<c04c7a9c>] __dev_queue_xmit+0x2c8/0x513
  76 [  348.530014]  [<c04c7cfb>] dev_queue_xmit+0xa/0xc
  77 [  348.530014]  [<f91bfc7a>] batadv_send_skb_packet+0xd6/0xec [batman_adv]
  78 [  348.530014]  [<f91bfdc4>] batadv_send_unicast_skb+0x15/0x4a [batman_adv]
  79 [  348.530014]  [<f91b5938>] batadv_dat_send_data+0x27e/0x310 [batman_adv]
  80 [  348.530014]  [<f91c30b5>] ? batadv_tt_global_hash_find.isra.11+0x8/0xa [batman_adv]
  81 [  348.530014]  [<f91b63f3>] batadv_dat_snoop_outgoing_arp_request+0x208/0x23d [batman_adv]
  82 [  348.530014]  [<f91c0cd9>] batadv_interface_tx+0x206/0x385 [batman_adv]
  83 [  348.530014]  [<c04c769c>] dev_hard_start_xmit+0x1f8/0x267
  84 [  348.530014]  [<c04c7261>] ?  validate_xmit_skb.isra.120.part.121+0x10/0x253
  85 [  348.530014]  [<c04defc6>] sch_direct_xmit+0x8b/0x1b3
  86 [  348.530014]  [<c04c7a9c>] __dev_queue_xmit+0x2c8/0x513
  87 [  348.530014]  [<f80cbd2a>] ? igb_xmit_frame+0x57/0x72 [igb]
  88 [  348.530014]  [<c04c7cfb>] dev_queue_xmit+0xa/0xc
  89 [  348.530014]  [<f843a326>] br_dev_queue_push_xmit+0xeb/0xfb [bridge]
  90 [  348.530014]  [<f843a35f>] br_forward_finish+0x29/0x74 [bridge]
  91 [  348.530014]  [<f843a23b>] ? deliver_clone+0x3b/0x3b [bridge]
  92 [  348.530014]  [<f843a714>] __br_forward+0x89/0xe7 [bridge]
  93 [  348.530014]  [<f843a336>] ? br_dev_queue_push_xmit+0xfb/0xfb [bridge]
  94 [  348.530014]  [<f843a234>] deliver_clone+0x34/0x3b [bridge]
  95 [  348.530014]  [<f843a68b>] ? br_flood+0x95/0x95 [bridge]
  96 [  348.530014]  [<f843a66d>] br_flood+0x77/0x95 [bridge]
  97 [  348.530014]  [<f843a809>] br_flood_forward+0x13/0x1a [bridge]
  98 [  348.530014]  [<f843a68b>] ? br_flood+0x95/0x95 [bridge]
  99 [  348.530014]  [<f843b877>] br_handle_frame_finish+0x392/0x3db [bridge]
 100 [  348.530014]  [<c04e9b2b>] ? nf_iterate+0x2b/0x6b
 101 [  348.530014]  [<f843baa6>] br_handle_frame+0x1e6/0x240 [bridge]
 102 [  348.530014]  [<f843b4e5>] ? br_handle_local_finish+0x6a/0x6a [bridge]
 103 [  348.530014]  [<c04c4ba0>] __netif_receive_skb_core+0x43a/0x66b
 104 [  348.530014]  [<f843b8c0>] ? br_handle_frame_finish+0x3db/0x3db [bridge]
 105 [  348.530014]  [<c023cea4>] ? resched_curr+0x19/0x37
 106 [  348.530014]  [<c0240707>] ? check_preempt_wakeup+0xbf/0xfe
 107 [  348.530014]  [<c0255dec>] ? ktime_get_with_offset+0x5c/0xfc
 108 [  348.530014]  [<c04c4fc1>] __netif_receive_skb+0x47/0x55
 109 [  348.530014]  [<c04c57ba>] netif_receive_skb_internal+0x40/0x5a
 110 [  348.530014]  [<c04c61ef>] napi_gro_receive+0x3a/0x94
 111 [  348.530014]  [<f80ce8d5>] igb_poll+0x6fd/0x9ad [igb]
 112 [  348.530014]  [<c0242bd8>] ? swake_up_locked+0x14/0x26
 113 [  348.530014]  [<c04c5d29>] net_rx_action+0xde/0x250
 114 [  348.530014]  [<c022a743>] __do_softirq+0x8a/0x163
 115 [  348.530014]  [<c022a6b9>] ? __hrtimer_tasklet_trampoline+0x19/0x19
 116 [  348.530014]  [<c021100f>] do_softirq_own_stack+0x26/0x2c
 117 [  348.530014]  <IRQ>
 118 [  348.530014]  [<c022a957>] irq_exit+0x31/0x6f
 119 [  348.530014]  [<c0210eb2>] do_IRQ+0x8d/0xa0
 120 [  348.530014]  [<c058152c>] common_interrupt+0x2c/0x40
 121 [  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
 122 [  348.530014] EIP: [<f929245d>] ieee80211_mps_set_frame_flags+0x40/0xaa [mac80211] SS:ESP 0068:f6409a40
 123 [  348.530014] CR2: 0000000000020040
 124 [  348.530014] ---[ end trace 48556ac26779732e ]---
 125 [  348.530014] Kernel panic - not syncing: Fatal exception in interrupt
 126 [  348.530014] Kernel Offset: disabled
 127
 128 Cc: stable@vger.kernel.org
 129 Reported-by: Fred Veldini <fred.veldini@gmail.com>
 130 Tested-by: Fred Veldini <fred.veldini@gmail.com>
 131 Signed-off-by: Bob Copeland <me@bobcopeland.com>
 132 ---
 133
 134 --- a/net/mac80211/mesh.c
 135 +++ b/net/mac80211/mesh.c
 136 @@ -161,6 +161,10 @@ void mesh_sta_cleanup(struct sta_info *s
 137                 del_timer_sync(&sta->mesh->plink_timer);
 138         }
 139
 140 +       /* make sure no readers can access nexthop sta from here on */
 141 +       mesh_path_flush_by_nexthop(sta);
 142 +       synchronize_net();
 143 +
 144         if (changed)
 145                 ieee80211_mbss_info_change_notify(sdata, changed);
 146  }