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

Started byDmitry Vyukov <dvyukov@google.com>
First post2017-03-03 15:20 +0100
Last post2017-03-03 16:50 +0100
Articles 11 — 3 participants

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  Re: net/dccp: use-after-free in dccp_feat_activate_values Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 15:20 +0100
    Re: net/dccp: use-after-free in dccp_feat_activate_values Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 15:20 +0100
    Re: net/dccp: use-after-free in dccp_feat_activate_values Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 16:20 +0100
      Re: net/dccp: use-after-free in dccp_feat_activate_values Eric Dumazet <edumazet@google.com> - 2017-03-03 16:30 +0100
        Re: net/dccp: use-after-free in dccp_feat_activate_values Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-03 17:10 +0100
          Re: net/dccp: use-after-free in dccp_feat_activate_values Dmitry Vyukov <dvyukov@google.com> - 2017-03-05 14:30 +0100
    Re: net/dccp: use-after-free in dccp_feat_activate_values Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-03 16:30 +0100
      Re: net/dccp: use-after-free in dccp_feat_activate_values Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-03 16:30 +0100
      Re: net/dccp: use-after-free in dccp_feat_activate_values Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 18:00 +0100
    Re: net/dccp: use-after-free in dccp_feat_activate_values Dmitry Vyukov <dvyukov@google.com> - 2017-03-03 16:40 +0100
    Re: net/dccp: use-after-free in dccp_feat_activate_values Eric Dumazet <eric.dumazet@gmail.com> - 2017-03-03 16:50 +0100

#1591973 — Re: net/dccp: use-after-free in dccp_feat_activate_values

FromDmitry Vyukov <dvyukov@google.com>
Date2017-03-03 15:20 +0100
SubjectRe: net/dccp: use-after-free in dccp_feat_activate_values
Message-ID<tgWdQ-2m3-1@gated-at.bofh.it>
On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
> <andreyknvl@google.com> 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.



Cong, where exactly do we need to add bh_lock_sock()?

I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c

==================================================================
BUG: KASAN: use-after-free in dccp_feat_activate_values+0x94c/0xa90
net/dccp/feat.c:1541 at addr ffff880059f18998
Read of size 8 by task syz-executor/3952
CPU: 2 PID: 3952 Comm: syz-executor Not tainted 4.10.0+ #269
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+0x2ee/0x3ef lib/dump_stack.c:51
 kasan_object_err+0x1c/0x70 mm/kasan/report.c:166
 print_address_description mm/kasan/report.c:204 [inline]
 kasan_report_error mm/kasan/report.c:288 [inline]
 kasan_report.part.2+0x198/0x440 mm/kasan/report.c:310
 kasan_report mm/kasan/report.c:331 [inline]
 __asan_report_load8_noabort+0x29/0x30 mm/kasan/report.c:331
 dccp_feat_activate_values+0x94c/0xa90 net/dccp/feat.c:1541
 dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121
 dccp_v6_request_recv_sock+0x1f1/0x17e0 net/dccp/ipv6.c:457
 dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
 dccp_v6_rcv+0x653/0x1d10 net/dccp/ipv6.c:711
 ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
 dst_input include/net/dst.h:492 [inline]
 ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
 __netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
 __netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
 process_backlog+0x11e/0x730 net/core/dev.c:4837
 napi_poll net/core/dev.c:5171 [inline]
 net_rx_action+0xf0a/0x1980 net/core/dev.c:5236
 __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
 do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902
 </IRQ>
 do_softirq.part.21+0x2c0/0x300 kernel/softirq.c:328
 do_softirq kernel/softirq.c:176 [inline]
 __local_bh_enable_ip+0x24c/0x290 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+0xb85/0x2380 net/ipv6/ip6_output.c:124
 ip6_finish_output+0x2f9/0x950 net/ipv6/ip6_output.c:149
 NF_HOOK_COND include/linux/netfilter.h:246 [inline]
 ip6_output+0x1cb/0x8c0 net/ipv6/ip6_output.c:163
 ip6_xmit+0xc36/0x1e80 include/net/dst.h:486
 inet6_csk_xmit+0x320/0x5d0 net/ipv6/inet6_connection_sock.c:139
 dccp_transmit_skb+0xac5/0x10e0 net/dccp/output.c:141
 dccp_xmit_packet+0x20f/0x750 net/dccp/output.c:280
 dccp_write_xmit+0x168/0x1d0 net/dccp/output.c:362
 dccp_sendmsg+0x793/0xb00 net/dccp/proto.c:796
 inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:761
 sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 SYSC_sendto+0x660/0x810 net/socket.c:1685
 SyS_sendto+0x40/0x50 net/socket.c:1653
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x4458d9
RSP: 002b:00007f59f536bb58 EFLAGS: 00000282 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000000000000001a RCX: 00000000004458d9
RDX: 0000000000000037 RSI: 0000000020e62000 RDI: 000000000000001a
RBP: 00000000006e1b90 R08: 0000000020e62fe0 R09: 0000000000000020
R10: 0000000000008000 R11: 0000000000000282 R12: 0000000000708150
R13: 0000000020d0aff8 R14: 0000000000000004 R15: 0000000000000000
Object at ffff880059f18980, in cache kmalloc-64 size: 64
Allocated:
PID = 3932
 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+0xaa/0xd0 mm/kasan/kasan.c:605
 kmem_cache_alloc_trace+0x10b/0x6e0 mm/slab.c:3637
 kmalloc include/linux/slab.h:490 [inline]
 dccp_feat_entry_new+0x20b/0x400 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+0x1f1/0xc50 net/dccp/output.c:423
 dccp_v6_send_response+0x4ec/0xc20 net/dccp/ipv6.c:217
 dccp_v6_conn_request+0xab2/0x1100 net/dccp/ipv6.c:377
 dccp_rcv_state_process+0x50c/0x1650 net/dccp/input.c:606
 dccp_v6_do_rcv+0x20d/0x350 net/dccp/ipv6.c:632
 sk_backlog_rcv include/net/sock.h:896 [inline]
 __sk_receive_skb+0x350/0xca0 net/core/sock.c:479
 dccp_v6_rcv+0xb17/0x1d10 net/dccp/ipv6.c:742
 ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
 dst_input include/net/dst.h:492 [inline]
 ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
 __netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
 __netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
 process_backlog+0x11e/0x730 net/core/dev.c:4837
 napi_poll net/core/dev.c:5171 [inline]
 net_rx_action+0xf0a/0x1980 net/core/dev.c:5236
 __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
Freed:
PID = 24
 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+0x6f/0xb0 mm/kasan/kasan.c:578
 __cache_free mm/slab.c:3513 [inline]
 kfree+0xd3/0x250 mm/slab.c:3830
 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/0xa90 net/dccp/feat.c:1543
 dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121
 dccp_v6_request_recv_sock+0x1f1/0x17e0 net/dccp/ipv6.c:457
 dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
 dccp_v6_rcv+0x653/0x1d10 net/dccp/ipv6.c:711
 ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
 dst_input include/net/dst.h:492 [inline]
 ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
 __netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
 __netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
 process_backlog+0x11e/0x730 net/core/dev.c:4837
 napi_poll net/core/dev.c:5171 [inline]
 net_rx_action+0xf0a/0x1980 net/core/dev.c:5236
 __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
Memory state around the buggy address:
 ffff880059f18880: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
 ffff880059f18900: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff880059f18980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                            ^
 ffff880059f18a00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff880059f18a80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
==================================================================

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#1591976

FromDmitry Vyukov <dvyukov@google.com>
Date2017-03-03 15:20 +0100
Message-ID<tgWdQ-2m3-7@gated-at.bofh.it>
In reply to#1591973
On Fri, Mar 3, 2017 at 3:11 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
> On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>> On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
>> <andreyknvl@google.com> 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.
>
>
>
> Cong, where exactly do we need to add bh_lock_sock()?
>
> I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c
>
> ==================================================================
> BUG: KASAN: use-after-free in dccp_feat_activate_values+0x94c/0xa90
> net/dccp/feat.c:1541 at addr ffff880059f18998
> Read of size 8 by task syz-executor/3952
> CPU: 2 PID: 3952 Comm: syz-executor Not tainted 4.10.0+ #269
> 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+0x2ee/0x3ef lib/dump_stack.c:51
>  kasan_object_err+0x1c/0x70 mm/kasan/report.c:166
>  print_address_description mm/kasan/report.c:204 [inline]
>  kasan_report_error mm/kasan/report.c:288 [inline]
>  kasan_report.part.2+0x198/0x440 mm/kasan/report.c:310
>  kasan_report mm/kasan/report.c:331 [inline]
>  __asan_report_load8_noabort+0x29/0x30 mm/kasan/report.c:331
>  dccp_feat_activate_values+0x94c/0xa90 net/dccp/feat.c:1541
>  dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121
>  dccp_v6_request_recv_sock+0x1f1/0x17e0 net/dccp/ipv6.c:457
>  dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
>  dccp_v6_rcv+0x653/0x1d10 net/dccp/ipv6.c:711
>  ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
>  dst_input include/net/dst.h:492 [inline]
>  ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
>  __netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
>  __netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
>  process_backlog+0x11e/0x730 net/core/dev.c:4837
>  napi_poll net/core/dev.c:5171 [inline]
>  net_rx_action+0xf0a/0x1980 net/core/dev.c:5236
>  __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
>  do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902
>  </IRQ>
>  do_softirq.part.21+0x2c0/0x300 kernel/softirq.c:328
>  do_softirq kernel/softirq.c:176 [inline]
>  __local_bh_enable_ip+0x24c/0x290 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+0xb85/0x2380 net/ipv6/ip6_output.c:124
>  ip6_finish_output+0x2f9/0x950 net/ipv6/ip6_output.c:149
>  NF_HOOK_COND include/linux/netfilter.h:246 [inline]
>  ip6_output+0x1cb/0x8c0 net/ipv6/ip6_output.c:163
>  ip6_xmit+0xc36/0x1e80 include/net/dst.h:486
>  inet6_csk_xmit+0x320/0x5d0 net/ipv6/inet6_connection_sock.c:139
>  dccp_transmit_skb+0xac5/0x10e0 net/dccp/output.c:141
>  dccp_xmit_packet+0x20f/0x750 net/dccp/output.c:280
>  dccp_write_xmit+0x168/0x1d0 net/dccp/output.c:362
>  dccp_sendmsg+0x793/0xb00 net/dccp/proto.c:796
>  inet_sendmsg+0x164/0x5b0 net/ipv4/af_inet.c:761
>  sock_sendmsg_nosec net/socket.c:633 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:643
>  SYSC_sendto+0x660/0x810 net/socket.c:1685
>  SyS_sendto+0x40/0x50 net/socket.c:1653
>  entry_SYSCALL_64_fastpath+0x1f/0xc2
> RIP: 0033:0x4458d9
> RSP: 002b:00007f59f536bb58 EFLAGS: 00000282 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 000000000000001a RCX: 00000000004458d9
> RDX: 0000000000000037 RSI: 0000000020e62000 RDI: 000000000000001a
> RBP: 00000000006e1b90 R08: 0000000020e62fe0 R09: 0000000000000020
> R10: 0000000000008000 R11: 0000000000000282 R12: 0000000000708150
> R13: 0000000020d0aff8 R14: 0000000000000004 R15: 0000000000000000
> Object at ffff880059f18980, in cache kmalloc-64 size: 64
> Allocated:
> PID = 3932
>  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+0xaa/0xd0 mm/kasan/kasan.c:605
>  kmem_cache_alloc_trace+0x10b/0x6e0 mm/slab.c:3637
>  kmalloc include/linux/slab.h:490 [inline]
>  dccp_feat_entry_new+0x20b/0x400 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+0x1f1/0xc50 net/dccp/output.c:423
>  dccp_v6_send_response+0x4ec/0xc20 net/dccp/ipv6.c:217
>  dccp_v6_conn_request+0xab2/0x1100 net/dccp/ipv6.c:377
>  dccp_rcv_state_process+0x50c/0x1650 net/dccp/input.c:606
>  dccp_v6_do_rcv+0x20d/0x350 net/dccp/ipv6.c:632
>  sk_backlog_rcv include/net/sock.h:896 [inline]
>  __sk_receive_skb+0x350/0xca0 net/core/sock.c:479
>  dccp_v6_rcv+0xb17/0x1d10 net/dccp/ipv6.c:742
>  ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
>  dst_input include/net/dst.h:492 [inline]
>  ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
>  __netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
>  __netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
>  process_backlog+0x11e/0x730 net/core/dev.c:4837
>  napi_poll net/core/dev.c:5171 [inline]
>  net_rx_action+0xf0a/0x1980 net/core/dev.c:5236
>  __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
> Freed:
> PID = 24
>  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+0x6f/0xb0 mm/kasan/kasan.c:578
>  __cache_free mm/slab.c:3513 [inline]
>  kfree+0xd3/0x250 mm/slab.c:3830
>  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/0xa90 net/dccp/feat.c:1543
>  dccp_create_openreq_child+0x464/0x610 net/dccp/minisocks.c:121
>  dccp_v6_request_recv_sock+0x1f1/0x17e0 net/dccp/ipv6.c:457
>  dccp_check_req+0x335/0x5a0 net/dccp/minisocks.c:186
>  dccp_v6_rcv+0x653/0x1d10 net/dccp/ipv6.c:711
>  ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
>  dst_input include/net/dst.h:492 [inline]
>  ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
>  NF_HOOK include/linux/netfilter.h:257 [inline]
>  ipv6_rcv+0x12df/0x2380 net/ipv6/ip6_input.c:203
>  __netif_receive_skb_core+0x1ac8/0x33f0 net/core/dev.c:4179
>  __netif_receive_skb+0x2a/0x170 net/core/dev.c:4217
>  process_backlog+0x11e/0x730 net/core/dev.c:4837
>  napi_poll net/core/dev.c:5171 [inline]
>  net_rx_action+0xf0a/0x1980 net/core/dev.c:5236
>  __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
> Memory state around the buggy address:
>  ffff880059f18880: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>  ffff880059f18900: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>>ffff880059f18980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>                             ^
>  ffff880059f18a00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff880059f18a80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================



Hit this while trying to reproduce another WARNING in networking
stack, so now I suspect that it may be an induced WARNING and not sure
if it worth pursuing spending more time on it...


WARNING: CPU: 1 PID: 29691 at net/core/stream.c:198
sk_stream_kill_queues+0x401/0x570 net/core/stream.c:198
Call Trace:
 __dump_stack lib/dump_stack.c:15 [inline]
 dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
 panic+0x1fb/0x412 kernel/panic.c:179
 __warn+0x1c4/0x1e0 kernel/panic.c:539
 warn_slowpath_null+0x2c/0x40 kernel/panic.c:582
 sk_stream_kill_queues+0x401/0x570 net/core/stream.c:198
 inet_csk_destroy_sock+0x175/0x450 net/ipv4/inet_connection_sock.c:708
 dccp_close+0x951/0xc60 net/dccp/proto.c:1067
 inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:431
 sock_release+0x8d/0x1e0 net/socket.c:599
 sock_close+0x16/0x20 net/socket.c:1063
 __fput+0x332/0x7f0 fs/file_table.c:208
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x18a/0x260 kernel/task_work.c:116
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0x18ef/0x28b0 kernel/exit.c:841
 do_group_exit+0x149/0x420 kernel/exit.c:945
 get_signal+0x7e0/0x1820 kernel/signal.c:2313
 do_signal+0xd2/0x2190 arch/x86/kernel/signal.c:807
 exit_to_usermode_loop+0x200/0x2a0 arch/x86/entry/common.c:156
 prepare_exit_to_usermode arch/x86/entry/common.c:190 [inline]
 syscall_return_slowpath+0x4d3/0x570 arch/x86/entry/common.c:259
 entry_SYSCALL_64_fastpath+0xc0/0xc2

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#1592039

FromDmitry Vyukov <dvyukov@google.com>
Date2017-03-03 16:20 +0100
Message-ID<tgX9T-31z-5@gated-at.bofh.it>
In reply to#1591973
On Fri, Mar 3, 2017 at 4:06 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
> On Fri, Mar 3, 2017 at 3:48 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> On Fri, 2017-03-03 at 06:32 -0800, Eric Dumazet wrote:
>>> On Fri, 2017-03-03 at 15:11 +0100, Dmitry Vyukov wrote:
>>> > On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>>> > > On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
>>> > > <andreyknvl@google.com> 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.
>>> >
>>> >
>>> >
>>> > Cong, where exactly do we need to add bh_lock_sock()?
>>> >
>>> > I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c
>>>
>>>
>>> I would try :
>>
>> Or something that would compile. I will take a deeper look after my
>> commute.
>
>
> Something that compiles is definitely better :)
> Reapplied.
>
>
>> diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
>> index 409d0cfd34474812c3bf74f26cd423a3d65ee441..56f883b301ccd610fc24efeac4fb47d3c2f95ecf 100644
>> --- a/net/dccp/ipv4.c
>> +++ b/net/dccp/ipv4.c
>> @@ -482,7 +482,11 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
>>         if (dst == NULL)
>>                 goto out;
>>
>> +       /* DCCP is not ready yet for lockless SYN processing */
>> +       bh_lock_sock((struct sock *)sk);
>>         skb = dccp_make_response(sk, dst, req);
>> +       bh_unlock_sock((struct sock *)sk);
>> +
>>         if (skb != NULL) {
>>                 const struct inet_request_sock *ireq = inet_rsk(req);
>>                 struct dccp_hdr *dh = dccp_hdr(skb);
>> diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
>> index 233b57367758c64c09ed40f7359cb8fcb1918d93..673f45f85b7c755c8165c6274ffb6b1fe5660683 100644
>> --- a/net/dccp/ipv6.c
>> +++ b/net/dccp/ipv6.c
>> @@ -214,7 +214,11 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req
>>                 goto done;
>>         }
>>
>> +       /* DCCP is not ready yet for lockless SYN processing */
>> +       bh_lock_sock((struct sock *)sk);
>>         skb = dccp_make_response(sk, dst, req);
>> +       bh_unlock_sock((struct sock *)sk);
>> +
>>         if (skb != NULL) {
>>                 struct dccp_hdr *dh = dccp_hdr(skb);
>>                 struct ipv6_txoptions *opt;
>>
>>


The first bot that picked this up started spewing:

BUG: spinlock recursion on CPU#1, syz-executor2/9452
 lock: 0xffff8801cd09abc8, .magic: dead4ead, .owner:
syz-executor2/9452, .owner_cpu: 1
CPU: 1 PID: 9452 Comm: syz-executor2 Not tainted 4.10.0+ #14
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:15 [inline]
 dump_stack+0x2ee/0x3ef lib/dump_stack.c:51
 spin_dump+0x14d/0x280 kernel/locking/spinlock_debug.c:67
 spin_bug kernel/locking/spinlock_debug.c:75 [inline]
 debug_spin_lock_before kernel/locking/spinlock_debug.c:84 [inline]
 do_raw_spin_lock+0x3dd/0x5b0 kernel/locking/spinlock_debug.c:135
 __raw_spin_lock include/linux/spinlock_api_smp.h:145 [inline]
 _raw_spin_lock+0x3b/0x50 kernel/locking/spinlock.c:151
 spin_lock include/linux/spinlock.h:302 [inline]
 dccp_v6_send_response+0x4f0/0xc40 net/dccp/ipv6.c:217
 dccp_v6_conn_request+0xab2/0x1100 net/dccp/ipv6.c:379
 dccp_rcv_state_process+0x51d/0x1680 net/dccp/input.c:611
 dccp_v6_do_rcv+0x20d/0x350 net/dccp/ipv6.c:634
 sk_backlog_rcv include/net/sock.h:893 [inline]
 __sk_receive_skb+0x350/0xca0 net/core/sock.c:479
 dccp_v6_rcv+0xb17/0x1d10 net/dccp/ipv6.c:744
 ip6_input_finish+0x45b/0x1700 net/ipv6/ip6_input.c:279
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ip6_input+0xdb/0x580 net/ipv6/ip6_input.c:322
 dst_input include/net/dst.h:507 [inline]
 ip6_rcv_finish+0x194/0x720 net/ipv6/ip6_input.c:69
 NF_HOOK include/linux/netfilter.h:257 [inline]
 ipv6_rcv+0x12d6/0x23b0 net/ipv6/ip6_input.c:203
 __netif_receive_skb_core+0x1fb9/0x3390 net/core/dev.c:4224
 __netif_receive_skb+0x2a/0x170 net/core/dev.c:4262
 process_backlog+0x11e/0x730 net/core/dev.c:4873
 napi_poll net/core/dev.c:5236 [inline]
 net_rx_action+0xeb4/0x1580 net/core/dev.c:5301
 __do_softirq+0x31f/0xbe7 kernel/softirq.c:284
 do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:902
 </IRQ>
 do_softirq.part.21+0x2c0/0x300 kernel/softirq.c:328
 do_softirq kernel/softirq.c:176 [inline]
 __local_bh_enable_ip+0x24c/0x290 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+0xb0c/0x22f0 net/ipv6/ip6_output.c:123
 ip6_finish_output+0x2f9/0x950 net/ipv6/ip6_output.c:148
 NF_HOOK_COND include/linux/netfilter.h:246 [inline]
 ip6_output+0x1cb/0x8c0 net/ipv6/ip6_output.c:162
 ip6_xmit+0xc36/0x1e90 include/net/dst.h:501
 inet6_csk_xmit+0x320/0x5d0 net/ipv6/inet6_connection_sock.c:179
 dccp_transmit_skb+0xac5/0x10e0 net/dccp/output.c:141
 dccp_connect+0x376/0x680 net/dccp/output.c:563
 dccp_v6_connect+0xcbe/0x18c0 net/dccp/ipv6.c:916
 __inet_stream_connect+0x882/0xea0 net/ipv4/af_inet.c:604
 inet_stream_connect+0x55/0xa0 net/ipv4/af_inet.c:665
 SYSC_connect+0x251/0x580 net/socket.c:1579
 SyS_connect+0x24/0x30 net/socket.c:1560
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x44fb79
RSP: 002b:00007fa5aef1ab58 EFLAGS: 00000212 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000020e5afe0 RCX: 000000000044fb79
RDX: 0000000000000020 RSI: 0000000020e5afe0 RDI: 0000000000000005
RBP: 0000000000000005 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000708000
R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000000000

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#1592055

FromEric Dumazet <edumazet@google.com>
Date2017-03-03 16:30 +0100
Message-ID<tgXjA-35T-37@gated-at.bofh.it>
In reply to#1592039
On Fri, Mar 3, 2017 at 7:12 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
> The first bot that picked this up started spewing:
>
> BUG: spinlock recursion on CPU#1, syz-executor2/9452

Yes. The bug is not about locking the listener, but protecting fields
of struct dccp_request_sock

I will provide a patch, once I reach the office and after the breakfast ;)

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#1592099

FromEric Dumazet <eric.dumazet@gmail.com>
Date2017-03-03 17:10 +0100
Message-ID<tgXWi-3BQ-11@gated-at.bofh.it>
In reply to#1592055
On Fri, 2017-03-03 at 07:22 -0800, Eric Dumazet wrote:
> On Fri, Mar 3, 2017 at 7:12 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
> > The first bot that picked this up started spewing:
> >
> > BUG: spinlock recursion on CPU#1, syz-executor2/9452
> 
> Yes. The bug is not about locking the listener, but protecting fields
> of struct dccp_request_sock
> 
> I will provide a patch, once I reach the office and after the breakfast ;)

OK here is what I suggest to fix the races.

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 61d042bbbf607253033d9948b291cab2322814ba..68449293c4b6233c1a1d4133b1819376a9310225 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -163,6 +163,7 @@ struct dccp_request_sock {
 	__u64			 dreq_isr;
 	__u64			 dreq_gsr;
 	__be32			 dreq_service;
+	spinlock_t		 dreq_lock;
 	struct list_head	 dreq_featneg;
 	__u32			 dreq_timestamp_echo;
 	__u32			 dreq_timestamp_time;
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index e267e6f4c9a5566b369a03a600a408e5bd41cbad..abd07a443219853b022bef41cb072e90ff8f07f0 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -142,6 +142,13 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
 	struct dccp_request_sock *dreq = dccp_rsk(req);
 	bool own_req;
 
+	/* TCP/DCCP listeners became lockless.
+	 * DCCP stores complex state in its request_sock, so we need
+	 * a protection for them, now this code runs without being protected
+	 * by the parent (listener) lock.
+	 */
+	spin_lock_bh(&dreq->dreq_lock);
+
 	/* Check for retransmitted REQUEST */
 	if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
 
@@ -156,7 +163,7 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
 			inet_rtx_syn_ack(sk, req);
 		}
 		/* Network Duplicate, discard packet */
-		return NULL;
+		goto out;
 	}
 
 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
@@ -182,20 +189,20 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
 
 	child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
 							 req, &own_req);
-	if (!child)
-		goto listen_overflow;
-
-	return inet_csk_complete_hashdance(sk, child, req, own_req);
+	if (child) {
+		child = inet_csk_complete_hashdance(sk, child, req, own_req);
+		goto out;
+	}
 
-listen_overflow:
-	dccp_pr_debug("listen_overflow!\n");
 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 drop:
 	if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
 		req->rsk_ops->send_reset(sk, skb);
 
 	inet_csk_reqsk_queue_drop(sk, req);
-	return NULL;
+out:
+	spin_unlock_bh(&dreq->dreq_lock);
+	return child;
 }
 
 EXPORT_SYMBOL_GPL(dccp_check_req);
@@ -246,6 +253,7 @@ int dccp_reqsk_init(struct request_sock *req,
 {
 	struct dccp_request_sock *dreq = dccp_rsk(req);
 
+	spin_lock_init(&dreq->dreq_lock);
 	inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
 	inet_rsk(req)->ir_num	   = ntohs(dccp_hdr(skb)->dccph_dport);
 	inet_rsk(req)->acked	   = 0;

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#1592761

FromDmitry Vyukov <dvyukov@google.com>
Date2017-03-05 14:30 +0100
Message-ID<thEoy-Sb-7@gated-at.bofh.it>
In reply to#1592099
On Fri, Mar 3, 2017 at 5:00 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Fri, 2017-03-03 at 07:22 -0800, Eric Dumazet wrote:
>> On Fri, Mar 3, 2017 at 7:12 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
>> > The first bot that picked this up started spewing:
>> >
>> > BUG: spinlock recursion on CPU#1, syz-executor2/9452
>>
>> Yes. The bug is not about locking the listener, but protecting fields
>> of struct dccp_request_sock
>>
>> I will provide a patch, once I reach the office and after the breakfast ;)
>
> OK here is what I suggest to fix the races.

I've applied the patch 2 days ago and it stopped happening since then.
Please mail an official patch.

Tested-by: Dmitry Vyukov <dvyukov@google.com>



> diff --git a/include/linux/dccp.h b/include/linux/dccp.h
> index 61d042bbbf607253033d9948b291cab2322814ba..68449293c4b6233c1a1d4133b1819376a9310225 100644
> --- a/include/linux/dccp.h
> +++ b/include/linux/dccp.h
> @@ -163,6 +163,7 @@ struct dccp_request_sock {
>         __u64                    dreq_isr;
>         __u64                    dreq_gsr;
>         __be32                   dreq_service;
> +       spinlock_t               dreq_lock;
>         struct list_head         dreq_featneg;
>         __u32                    dreq_timestamp_echo;
>         __u32                    dreq_timestamp_time;
> diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
> index e267e6f4c9a5566b369a03a600a408e5bd41cbad..abd07a443219853b022bef41cb072e90ff8f07f0 100644
> --- a/net/dccp/minisocks.c
> +++ b/net/dccp/minisocks.c
> @@ -142,6 +142,13 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
>         struct dccp_request_sock *dreq = dccp_rsk(req);
>         bool own_req;
>
> +       /* TCP/DCCP listeners became lockless.
> +        * DCCP stores complex state in its request_sock, so we need
> +        * a protection for them, now this code runs without being protected
> +        * by the parent (listener) lock.
> +        */
> +       spin_lock_bh(&dreq->dreq_lock);
> +
>         /* Check for retransmitted REQUEST */
>         if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
>
> @@ -156,7 +163,7 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
>                         inet_rtx_syn_ack(sk, req);
>                 }
>                 /* Network Duplicate, discard packet */
> -               return NULL;
> +               goto out;
>         }
>
>         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
> @@ -182,20 +189,20 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
>
>         child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
>                                                          req, &own_req);
> -       if (!child)
> -               goto listen_overflow;
> -
> -       return inet_csk_complete_hashdance(sk, child, req, own_req);
> +       if (child) {
> +               child = inet_csk_complete_hashdance(sk, child, req, own_req);
> +               goto out;
> +       }
>
> -listen_overflow:
> -       dccp_pr_debug("listen_overflow!\n");
>         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
>  drop:
>         if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
>                 req->rsk_ops->send_reset(sk, skb);
>
>         inet_csk_reqsk_queue_drop(sk, req);
> -       return NULL;
> +out:
> +       spin_unlock_bh(&dreq->dreq_lock);
> +       return child;
>  }
>
>  EXPORT_SYMBOL_GPL(dccp_check_req);
> @@ -246,6 +253,7 @@ int dccp_reqsk_init(struct request_sock *req,
>  {
>         struct dccp_request_sock *dreq = dccp_rsk(req);
>
> +       spin_lock_init(&dreq->dreq_lock);
>         inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
>         inet_rsk(req)->ir_num      = ntohs(dccp_hdr(skb)->dccph_dport);
>         inet_rsk(req)->acked       = 0;
>
>

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#1592058

FromEric Dumazet <eric.dumazet@gmail.com>
Date2017-03-03 16:30 +0100
Message-ID<tgX9T-31z-9@gated-at.bofh.it>
In reply to#1591973
On Fri, 2017-03-03 at 06:32 -0800, Eric Dumazet wrote:
> On Fri, 2017-03-03 at 15:11 +0100, Dmitry Vyukov wrote:
> > On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > > On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
> > > <andreyknvl@google.com> 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.
> > 
> > 
> > 
> > Cong, where exactly do we need to add bh_lock_sock()?
> > 
> > I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c
> 
> 
> I would try :

Or something that would compile. I will take a deeper look after my
commute.

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 409d0cfd34474812c3bf74f26cd423a3d65ee441..56f883b301ccd610fc24efeac4fb47d3c2f95ecf 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -482,7 +482,11 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
 	if (dst == NULL)
 		goto out;
 
+	/* DCCP is not ready yet for lockless SYN processing */
+	bh_lock_sock((struct sock *)sk);
 	skb = dccp_make_response(sk, dst, req);
+	bh_unlock_sock((struct sock *)sk);
+
 	if (skb != NULL) {
 		const struct inet_request_sock *ireq = inet_rsk(req);
 		struct dccp_hdr *dh = dccp_hdr(skb);
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 233b57367758c64c09ed40f7359cb8fcb1918d93..673f45f85b7c755c8165c6274ffb6b1fe5660683 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -214,7 +214,11 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req
 		goto done;
 	}
 
+	/* DCCP is not ready yet for lockless SYN processing */
+	bh_lock_sock((struct sock *)sk);
 	skb = dccp_make_response(sk, dst, req);
+	bh_unlock_sock((struct sock *)sk);
+
 	if (skb != NULL) {
 		struct dccp_hdr *dh = dccp_hdr(skb);
 		struct ipv6_txoptions *opt;

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#1592061

FromEric Dumazet <eric.dumazet@gmail.com>
Date2017-03-03 16:30 +0100
Message-ID<tgXjB-35T-45@gated-at.bofh.it>
In reply to#1592058
On Fri, 2017-03-03 at 16:06 +0100, Dmitry Vyukov wrote:

> Something that compiles is definitely better :)
> Reapplied.

Just to be clear : This is not the proper patch. This only reduces the
race.

bh_lock_sock() does not prevent a user process from owning the socket.

We need another protection, probably RCU based, or another spinlock
protecting the fields needed at SYNACK generation.

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#1592139

FromDmitry Vyukov <dvyukov@google.com>
Date2017-03-03 18:00 +0100
Message-ID<tgX9T-31z-11@gated-at.bofh.it>
In reply to#1592058
On Fri, Mar 3, 2017 at 3:48 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Fri, 2017-03-03 at 06:32 -0800, Eric Dumazet wrote:
>> On Fri, 2017-03-03 at 15:11 +0100, Dmitry Vyukov wrote:
>> > On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>> > > On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
>> > > <andreyknvl@google.com> 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.
>> >
>> >
>> >
>> > Cong, where exactly do we need to add bh_lock_sock()?
>> >
>> > I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c
>>
>>
>> I would try :
>
> Or something that would compile. I will take a deeper look after my
> commute.


Something that compiles is definitely better :)
Reapplied.


> diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
> index 409d0cfd34474812c3bf74f26cd423a3d65ee441..56f883b301ccd610fc24efeac4fb47d3c2f95ecf 100644
> --- a/net/dccp/ipv4.c
> +++ b/net/dccp/ipv4.c
> @@ -482,7 +482,11 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
>         if (dst == NULL)
>                 goto out;
>
> +       /* DCCP is not ready yet for lockless SYN processing */
> +       bh_lock_sock((struct sock *)sk);
>         skb = dccp_make_response(sk, dst, req);
> +       bh_unlock_sock((struct sock *)sk);
> +
>         if (skb != NULL) {
>                 const struct inet_request_sock *ireq = inet_rsk(req);
>                 struct dccp_hdr *dh = dccp_hdr(skb);
> diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
> index 233b57367758c64c09ed40f7359cb8fcb1918d93..673f45f85b7c755c8165c6274ffb6b1fe5660683 100644
> --- a/net/dccp/ipv6.c
> +++ b/net/dccp/ipv6.c
> @@ -214,7 +214,11 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req
>                 goto done;
>         }
>
> +       /* DCCP is not ready yet for lockless SYN processing */
> +       bh_lock_sock((struct sock *)sk);
>         skb = dccp_make_response(sk, dst, req);
> +       bh_unlock_sock((struct sock *)sk);
> +
>         if (skb != NULL) {
>                 struct dccp_hdr *dh = dccp_hdr(skb);
>                 struct ipv6_txoptions *opt;
>
>

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#1592070

FromDmitry Vyukov <dvyukov@google.com>
Date2017-03-03 16:40 +0100
Message-ID<tgXtg-3ca-15@gated-at.bofh.it>
In reply to#1591973
On Fri, Mar 3, 2017 at 3:32 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>> > On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
>> > <andreyknvl@google.com> 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.
>>
>>
>>
>> Cong, where exactly do we need to add bh_lock_sock()?
>>
>> I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c
>
>
> I would try :
>
> diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
> index 409d0cfd34474812c3bf74f26cd423a3d65ee441..5a8b5ac5edaaf35428ab04cc810d98310bd169ed 100644
> --- a/net/dccp/ipv4.c
> +++ b/net/dccp/ipv4.c
> @@ -482,7 +482,9 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
>         if (dst == NULL)
>                 goto out;
>
> +       bh_lock_sock(sk);
>         skb = dccp_make_response(sk, dst, req);
> +       bh_unlock_sock(sk);
>         if (skb != NULL) {
>                 const struct inet_request_sock *ireq = inet_rsk(req);
>                 struct dccp_hdr *dh = dccp_hdr(skb);
> diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
> index 233b57367758c64c09ed40f7359cb8fcb1918d93..e89cc88d14c22d411a91afab093e209fcbb816d8 100644
> --- a/net/dccp/ipv6.c
> +++ b/net/dccp/ipv6.c
> @@ -214,7 +214,9 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req
>                 goto done;
>         }
>
> +       bh_lock_sock(sk);
>         skb = dccp_make_response(sk, dst, req);
> +       bh_unlock_sock(sk);
>         if (skb != NULL) {
>                 struct dccp_hdr *dh = dccp_hdr(skb);
>                 struct ipv6_txoptions *opt;


Applied on bots. Thanks!

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#1592074

FromEric Dumazet <eric.dumazet@gmail.com>
Date2017-03-03 16:50 +0100
Message-ID<tgX9T-31z-7@gated-at.bofh.it>
In reply to#1591973
On Fri, 2017-03-03 at 15:11 +0100, Dmitry Vyukov wrote:
> On Mon, Feb 13, 2017 at 11:29 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > On Mon, Feb 13, 2017 at 11:19 AM, Andrey Konovalov
> > <andreyknvl@google.com> 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.
> 
> 
> 
> Cong, where exactly do we need to add bh_lock_sock()?
> 
> I am still seeing this on 4977ab6e92e267afe9d8f78438c3db330ca8434c


I would try :

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 409d0cfd34474812c3bf74f26cd423a3d65ee441..5a8b5ac5edaaf35428ab04cc810d98310bd169ed 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -482,7 +482,9 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
 	if (dst == NULL)
 		goto out;
 
+	bh_lock_sock(sk);
 	skb = dccp_make_response(sk, dst, req);
+	bh_unlock_sock(sk);
 	if (skb != NULL) {
 		const struct inet_request_sock *ireq = inet_rsk(req);
 		struct dccp_hdr *dh = dccp_hdr(skb);
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 233b57367758c64c09ed40f7359cb8fcb1918d93..e89cc88d14c22d411a91afab093e209fcbb816d8 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -214,7 +214,9 @@ static int dccp_v6_send_response(const struct sock *sk, struct request_sock *req
 		goto done;
 	}
 
+	bh_lock_sock(sk);
 	skb = dccp_make_response(sk, dst, req);
+	bh_unlock_sock(sk);
 	if (skb != NULL) {
 		struct dccp_hdr *dh = dccp_hdr(skb);
 		struct ipv6_txoptions *opt;

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