Skip to content
  1. Aug 15, 2021
  2. Aug 10, 2021
  3. Aug 08, 2021
    • Greg Kroah-Hartman's avatar
    • Ziyang Xuan's avatar
      can: raw: raw_setsockopt(): fix raw_rcv panic for sock UAF · 19a3982a
      Ziyang Xuan authored
      commit 54f93336 upstream.
      
      We get a bug during ltp can_filter test as following.
      
      ===========================================
      [60919.264984] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
      [60919.265223] PGD 8000003dda726067 P4D 8000003dda726067 PUD 3dda727067 PMD 0
      [60919.265443] Oops: 0000 [#1] SMP PTI
      [60919.265550] CPU: 30 PID: 3638365 Comm: can_filter Kdump: loaded Tainted: G        W         4.19.90+ #1
      [60919.266068] RIP: 0010:selinux_socket_sock_rcv_skb+0x3e/0x200
      [60919.293289] RSP: 0018:ffff8d53bfc03cf8 EFLAGS: 00010246
      [60919.307140] RAX: 0000000000000000 RBX: 000000000000001d RCX: 0000000000000007
      [60919.320756] RDX: 0000000000000001 RSI: ffff8d5104a8ed00 RDI: ffff8d53bfc03d30
      [60919.334319] RBP: ffff8d9338056800 R08: ffff8d53bfc29d80 R09: 0000000000000001
      [60919.347969] R10: ffff8d53bfc03ec0 R11: ffffb8526ef47c98 R12: ffff8d53bfc03d30
      [60919.350320] perf: interrupt took too long (3063 > 2500), lowering kernel.perf_event_max_sample_rate to 65000
      [60919.361148] R13: 0000000000000001 R14: ffff8d53bcf90000 R15: 0000000000000000
      [60919.361151] FS:  00007fb78b6b3600(0000) GS:ffff8d53bfc00000(0000) knlGS:0000000000000000
      [60919.400812] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
      [60919.413730] CR2: 0000000000000010 CR3: 0000003e3f784006 CR4: 00000000007606e0
      [60919.426479] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
      [60919.439339] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
      [60919.451608] PKRU: 55555554
      [60919.463622] Call Trace:
      [60919.475617]  <IRQ>
      [60919.487122]  ? update_load_avg+0x89/0x5d0
      [60919.498478]  ? update_load_avg+0x89/0x5d0
      [60919.509822]  ? account_entity_enqueue+0xc5/0xf0
      [60919.520709]  security_sock_rcv_skb+0x2a/0x40
      [60919.531413]  sk_filter_trim_cap+0x47/0x1b0
      [60919.542178]  ? kmem_cache_alloc+0x38/0x1b0
      [60919.552444]  sock_queue_rcv_skb+0x17/0x30
      [60919.562477]  raw_rcv+0x110/0x190 [can_raw]
      [60919.572539]  can_rcv_filter+0xbc/0x1b0 [can]
      [60919.582173]  can_receive+0x6b/0xb0 [can]
      [60919.591595]  can_rcv+0x31/0x70 [can]
      [60919.600783]  __netif_receive_skb_one_core+0x5a/0x80
      [60919.609864]  process_backlog+0x9b/0x150
      [60919.618691]  net_rx_action+0x156/0x400
      [60919.627310]  ? sched_clock_cpu+0xc/0xa0
      [60919.635714]  __do_softirq+0xe8/0x2e9
      [60919.644161]  do_softirq_own_stack+0x2a/0x40
      [60919.652154]  </IRQ>
      [60919.659899]  do_softirq.part.17+0x4f/0x60
      [60919.667475]  __local_bh_enable_ip+0x60/0x70
      [60919.675089]  __dev_queue_xmit+0x539/0x920
      [60919.682267]  ? finish_wait+0x80/0x80
      [60919.689218]  ? finish_wait+0x80/0x80
      [60919.695886]  ? sock_alloc_send_pskb+0x211/0x230
      [60919.702395]  ? can_send+0xe5/0x1f0 [can]
      [60919.708882]  can_send+0xe5/0x1f0 [can]
      [60919.715037]  raw_sendmsg+0x16d/0x268 [can_raw]
      
      It's because raw_setsockopt() concurrently with
      unregister_netdevice_many(). Concurrent scenario as following.
      
      	cpu0						cpu1
      raw_bind
      raw_setsockopt					unregister_netdevice_many
      						unlist_netdevice
      dev_get_by_index				raw_notifier
      raw_enable_filters				......
      can_rx_register
      can_rcv_list_find(..., net->can.rx_alldev_list)
      
      ......
      
      sock_close
      raw_release(sock_a)
      
      ......
      
      can_receive
      can_rcv_filter(net->can.rx_alldev_list, ...)
      raw_rcv(skb, sock_a)
      BUG
      
      After unlist_netdevice(), dev_get_by_index() return NULL in
      raw_setsockopt(). Function raw_enable_filters() will add sock
      and can_filter to net->can.rx_alldev_list. Then the sock is closed.
      Followed by, we sock_sendmsg() to a new vcan device use the same
      can_filter. Protocol stack match the old receiver whose sock has
      been released on net->can.rx_alldev_list in can_rcv_filter().
      Function raw_rcv() uses the freed sock. UAF BUG is triggered.
      
      We can find that the key issue is that net_device has not been
      protected in raw_setsockopt(). Use rtnl_lock to protect net_device
      in raw_setsockopt().
      
      Fixes: c18ce101 ("[CAN]: Add raw protocol")
      Link: https://lore.kernel.org/r/20210722070819.1048263-1-william.xuanziyang@huawei.com
      
      
      Cc: linux-stable <stable@vger.kernel.org>
      Signed-off-by: default avatarZiyang Xuan <william.xuanziyang@huawei.com>
      Acked-by: default avatarOliver Hartkopp <socketcan@hartkopp.net>
      Signed-off-by: default avatarMarc Kleine-Budde <mkl@pengutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      19a3982a