Re: net/dccp: use-after-free in dccp_feat_activate_values

[Cong Wang]

On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
<andreyknvl@xxxxxxxxxx> wrote:
> Hi,
>
> I've got the following error report while fuzzing the kernel with syzkaller.
>
> On commit 926af6273fc683cd98cd0ce7bf0d04a02eed6742.
>
> A reproducer and .config are attached.
> Note, that it takes quite some time to trigger the bug (up to 10 minutes).
>
> BUG: KASAN: use-after-free in dccp_feat_activate_values+0x967/0xab0
> net/dccp/feat.c:1541 at addr ffff88003713be68
> Read of size 8 by task syz-executor2/8457
> CPU: 2 PID: 8457 Comm: syz-executor2 Not tainted 4.10.0-rc7+ #127
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  <IRQ>
>  __dump_stack lib/dump_stack.c:15 [inline]
>  dump_stack+0x292/0x398 lib/dump_stack.c:51
>  kasan_object_err+0x1c/0x70 mm/kasan/report.c:162
>  print_address_description mm/kasan/report.c:200 [inline]
>  kasan_report_error mm/kasan/report.c:289 [inline]
>  kasan_report.part.1+0x20e/0x4e0 mm/kasan/report.c:311
>  kasan_report mm/kasan/report.c:332 [inline]
>  __asan_report_load8_noabort+0x29/0x30 mm/kasan/report.c:332
>  dccp_feat_activate_values+0x967/0xab0 net/dccp/feat.c:1541
>  dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121
>  dccp_v6_request_recv_sock+0x1f6/0x1960 net/dccp/ipv6.c:457
>  dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
>  dccp_v6_rcv+0x69e/0x1d00 net/dccp/ipv6.c:711
>  ip6_input_finish+0x46d/0x17a0 net/ipv6/ip6_input.c:279
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ip6_input+0xdb/0x590 net/ipv6/ip6_input.c:322
>  dst_input include/net/dst.h:507 [inline]
>  ip6_rcv_finish+0x289/0x890 net/ipv6/ip6_input.c:69
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ipv6_rcv+0x12ec/0x23d0 net/ipv6/ip6_input.c:203
>  __netif_receive_skb_core+0x1ae5/0x3400 net/core/dev.c:4190
>  __netif_receive_skb+0x2a/0x170 net/core/dev.c:4228
>  process_backlog+0xe5/0x6c0 net/core/dev.c:4839
>  napi_poll net/core/dev.c:5202 [inline]
>  net_rx_action+0xe70/0x1900 net/core/dev.c:5267
>  __do_softirq+0x2fb/0xb7d kernel/softirq.c:284
>  do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902


Seems there is a race condition between iterating dccp_feat_entry
and freeing it, bh_lock_sock() seems not held in this path.


>  </IRQ>
>  do_softirq.part.17+0x1e8/0x230 kernel/softirq.c:328
>  do_softirq kernel/softirq.c:176 [inline]
>  __local_bh_enable_ip+0x1f2/0x200 kernel/softirq.c:181
>  local_bh_enable include/linux/bottom_half.h:31 [inline]
>  rcu_read_unlock_bh include/linux/rcupdate.h:971 [inline]
>  ip6_finish_output2+0xbb0/0x23d0 net/ipv6/ip6_output.c:123
>  ip6_finish_output+0x302/0x960 net/ipv6/ip6_output.c:148
>  NF_HOOK_COND include/linux/netfilter.h:246 [inline]
>  ip6_output+0x1cb/0x8d0 net/ipv6/ip6_output.c:162
>  ip6_xmit+0xcdf/0x20d0 include/net/dst.h:501
>  inet6_csk_xmit+0x320/0x5f0 net/ipv6/inet6_connection_sock.c:179
>  dccp_transmit_skb+0xb09/0x1120 net/dccp/output.c:141
>  dccp_xmit_packet+0x215/0x760 net/dccp/output.c:280
>  dccp_write_xmit+0x168/0x1d0 net/dccp/output.c:362
>  dccp_sendmsg+0x79c/0xb10 net/dccp/proto.c:796
>  inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:744
>  sock_sendmsg_nosec net/socket.c:635 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:645
>  SYSC_sendto+0x660/0x810 net/socket.c:1687
>  SyS_sendto+0x40/0x50 net/socket.c:1655
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: 0033:0x4458b9
> RSP: 002b:00007f8ceb77bb58 EFLAGS: 00000282 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 0000000000000017 RCX: 00000000004458b9
> RDX: 0000000000000023 RSI: 0000000020e60000 RDI: 0000000000000017
> RBP: 00000000006e1b90 R08: 00000000200f9fe1 R09: 0000000000000020
> R10: 0000000000008010 R11: 0000000000000282 R12: 00000000007080a8
> R13: 0000000000000000 R14: 00007f8ceb77c9c0 R15: 00007f8ceb77c700
> Object at ffff88003713be50, in cache kmalloc-64 size: 64
> Allocated:
> PID = 8446
>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>  set_track mm/kasan/kasan.c:514 [inline]
>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:605
>  kmem_cache_alloc_trace+0x82/0x270 mm/slub.c:2738
>  kmalloc include/linux/slab.h:490 [inline]
>  dccp_feat_entry_new+0x214/0x410 net/dccp/feat.c:467
>  dccp_feat_push_change+0x38/0x220 net/dccp/feat.c:487
>  __feat_register_sp+0x223/0x2f0 net/dccp/feat.c:741
>  dccp_feat_propagate_ccid+0x22b/0x2b0 net/dccp/feat.c:949
>  dccp_feat_server_ccid_dependencies+0x1b3/0x250 net/dccp/feat.c:1012
>  dccp_make_response+0x1f1/0xc90 net/dccp/output.c:423
>  dccp_v6_send_response+0x4ec/0xc20 net/dccp/ipv6.c:217
>  dccp_v6_conn_request+0xaba/0x11b0 net/dccp/ipv6.c:377
>  dccp_rcv_state_process+0x51e/0x1650 net/dccp/input.c:606
>  dccp_v6_do_rcv+0x213/0x350 net/dccp/ipv6.c:632
>  sk_backlog_rcv include/net/sock.h:893 [inline]
>  __sk_receive_skb+0x36f/0xcc0 net/core/sock.c:479
>  dccp_v6_rcv+0xba5/0x1d00 net/dccp/ipv6.c:742
>  ip6_input_finish+0x46d/0x17a0 net/ipv6/ip6_input.c:279
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ip6_input+0xdb/0x590 net/ipv6/ip6_input.c:322
>  dst_input include/net/dst.h:507 [inline]
>  ip6_rcv_finish+0x289/0x890 net/ipv6/ip6_input.c:69
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ipv6_rcv+0x12ec/0x23d0 net/ipv6/ip6_input.c:203
>  __netif_receive_skb_core+0x1ae5/0x3400 net/core/dev.c:4190
>  __netif_receive_skb+0x2a/0x170 net/core/dev.c:4228
>  process_backlog+0xe5/0x6c0 net/core/dev.c:4839
>  napi_poll net/core/dev.c:5202 [inline]
>  net_rx_action+0xe70/0x1900 net/core/dev.c:5267
>  __do_softirq+0x2fb/0xb7d kernel/softirq.c:284
> Freed:
> PID = 15
>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>  set_track mm/kasan/kasan.c:514 [inline]
>  kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:578
>  slab_free_hook mm/slub.c:1355 [inline]
>  slab_free_freelist_hook mm/slub.c:1377 [inline]
>  slab_free mm/slub.c:2954 [inline]
>  kfree+0xe8/0x2b0 mm/slub.c:3874
>  dccp_feat_entry_destructor.part.4+0x48/0x60 net/dccp/feat.c:418
>  dccp_feat_entry_destructor net/dccp/feat.c:416 [inline]
>  dccp_feat_list_pop net/dccp/feat.c:541 [inline]
>  dccp_feat_activate_values+0x57f/0xab0 net/dccp/feat.c:1543
>  dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121
>  dccp_v6_request_recv_sock+0x1f6/0x1960 net/dccp/ipv6.c:457
>  dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
>  dccp_v6_rcv+0x69e/0x1d00 net/dccp/ipv6.c:711
>  ip6_input_finish+0x46d/0x17a0 net/ipv6/ip6_input.c:279
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ip6_input+0xdb/0x590 net/ipv6/ip6_input.c:322
>  dst_input include/net/dst.h:507 [inline]
>  ip6_rcv_finish+0x289/0x890 net/ipv6/ip6_input.c:69
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ipv6_rcv+0x12ec/0x23d0 net/ipv6/ip6_input.c:203
>  __netif_receive_skb_core+0x1ae5/0x3400 net/core/dev.c:4190
>  __netif_receive_skb+0x2a/0x170 net/core/dev.c:4228
>  process_backlog+0xe5/0x6c0 net/core/dev.c:4839
>  napi_poll net/core/dev.c:5202 [inline]
>  net_rx_action+0xe70/0x1900 net/core/dev.c:5267
>  __do_softirq+0x2fb/0xb7d kernel/softirq.c:284
> Memory state around the buggy address:
>  ffff88003713bd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88003713bd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>ffff88003713be00: fc fc fc fc fc fc fc fc fc fc fb fb fb fb fb fb
>                                                           ^
>  ffff88003713be80: fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff88003713bf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
> Disabling lock debugging due to kernel taint
> Kernel panic - not syncing: panic_on_warn set ...