Date:   Wed, 22 Nov 2017 07:58:47 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Craig Gallek <kraig@...gle.com>,
        David Miller <davem@...emloft.net>,
        Networking <netdev@...r.kernel.org>
Subject: Re: Uninitialized value in __sk_nulls_add_node_rcu()

On Wed, Nov 22, 2017 at 5:38 AM, Alexander Potapenko <glider@...gle.com> wrote:
> On Thu, Oct 26, 2017 at 4:56 PM, Alexander Potapenko <glider@...gle.com> wrote:
>> On Thu, Oct 26, 2017 at 4:52 PM, Eric Dumazet <edumazet@...gle.com> wrote:
>>> On Thu, Oct 26, 2017 at 7:47 AM, Eric Dumazet <edumazet@...gle.com> wrote:
>>>> On Thu, Oct 26, 2017 at 7:20 AM, Alexander Potapenko <glider@...gle.com> wrote:
>>>>> On Thu, Oct 26, 2017 at 2:51 PM, Alexander Potapenko <glider@...gle.com> wrote:
>>>>>> Hi David, Eric,
>>>>>>
>>>>>> I've changed KMSAN instrumentation a bit and it's now reporting a new
>>>>>> error (see below) when I SSH into a VM.
>>>>> I've double-checked the old instrumentation and found a bug in it,
>>>>> which led to masking some of the errors on uninitialized bitfields.
>>>>> I now believe this is a true positive report.
>>>>
>>>>
>>>> Please do not top post on netdev
>> Sorry about that.
>>>> A child is cloned from the listener, check sock_copy()
>>>>
>>>> sk_reuseport is part of the copied fields.
>>>>
>>>> You might have some bug at your side ?
>>>>
>>>
>>> Oh these are request socket.
>>>
>>> This is an harmless bug added in commit d894ba18d4e449b3a7f6eb491f16c9e02933736e
>>> ("soreuseport: fix ordering for mixed v4/v6 sockets")
>>>
>>> I will send a patch, but really this has no effect at all.
>> Thanks for clarifying!
>> For me this was a question of the tool's correctness, because until
>> recently I wasn't able to understand whether this is a true bug or
>> not.
> A friendly ping.
> Eric, did you find the time to send the patch?

Not yet, I am still investigating this issue.

Thanks.

>>>>
>>>>>> For |req| allocated by inet_reqsk_alloc() the value of
>>>>>> req_to_sk(req)->sk_reuseport is uninitialized.
>>>>>> Does this look valid?
>>>>>> I'm a bit surprised this didn't show up before, but I couldn't find
>>>>>> any code to initialize sk_reuseport.
>>>>>>
>>>>>> ==================================================================
>>>>>> BUG: KMSAN: use of uninitialized memory in inet_ehash_insert+0xd40/0x1050
>>>>>> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.13.0+ #3288
>>>>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>>>>>> Call Trace:
>>>>>>  <IRQ>
>>>>>>  __dump_stack lib/dump_stack.c:16
>>>>>>  dump_stack+0x185/0x1d0 lib/dump_stack.c:52
>>>>>>  kmsan_report+0x13f/0x1c0 mm/kmsan/kmsan.c:1016
>>>>>>  __msan_warning_32+0x69/0xb0 mm/kmsan/kmsan_instr.c:766
>>>>>>  __sk_nulls_add_node_rcu ./include/net/sock.h:684
>>>>>>  inet_ehash_insert+0xd40/0x1050 net/ipv4/inet_hashtables.c:413
>>>>>>  reqsk_queue_hash_req net/ipv4/inet_connection_sock.c:754
>>>>>>  inet_csk_reqsk_queue_hash_add+0x1cc/0x300 net/ipv4/inet_connection_sock.c:765
>>>>>>  tcp_conn_request+0x31e7/0x36f0 net/ipv4/tcp_input.c:6414
>>>>>>  tcp_v4_conn_request+0x16d/0x220 net/ipv4/tcp_ipv4.c:1314
>>>>>>  tcp_rcv_state_process+0x42a/0x7210 net/ipv4/tcp_input.c:5917
>>>>>>  tcp_v4_do_rcv+0xa6a/0xcd0 net/ipv4/tcp_ipv4.c:1483
>>>>>>  tcp_v4_rcv+0x3de0/0x4ab0 net/ipv4/tcp_ipv4.c:1763
>>>>>>  ip_local_deliver_finish+0x6bb/0xcb0 net/ipv4/ip_input.c:216
>>>>>>  NF_HOOK ./include/linux/netfilter.h:248
>>>>>>  ip_local_deliver+0x3fa/0x480 net/ipv4/ip_input.c:257
>>>>>>  dst_input ./include/net/dst.h:477
>>>>>>  ip_rcv_finish+0x6fb/0x1540 net/ipv4/ip_input.c:397
>>>>>>  NF_HOOK ./include/linux/netfilter.h:248
>>>>>>  ip_rcv+0x10f6/0x15c0 net/ipv4/ip_input.c:488
>>>>>>  __netif_receive_skb_core+0x36f6/0x3f60 net/core/dev.c:4298
>>>>>>  __netif_receive_skb net/core/dev.c:4336
>>>>>>  netif_receive_skb_internal+0x63c/0x19c0 net/core/dev.c:4497
>>>>>>  napi_skb_finish net/core/dev.c:4858
>>>>>>  napi_gro_receive+0x629/0xa50 net/core/dev.c:4889
>>>>>>  e1000_receive_skb drivers/net/ethernet/intel/e1000/e1000_main.c:4018
>>>>>>  e1000_clean_rx_irq+0x1492/0x1d30
>>>>>> drivers/net/ethernet/intel/e1000/e1000_main.c:4474
>>>>>>  e1000_clean+0x43aa/0x5970 drivers/net/ethernet/intel/e1000/e1000_main.c:3819
>>>>>>  napi_poll net/core/dev.c:5500
>>>>>>  net_rx_action+0x73c/0x1820 net/core/dev.c:5566
>>>>>>  __do_softirq+0x4b4/0x8dd kernel/softirq.c:284
>>>>>>  invoke_softirq kernel/softirq.c:364
>>>>>>  irq_exit+0x203/0x240 kernel/softirq.c:405
>>>>>>  exiting_irq+0xe/0x10 ./arch/x86/include/asm/apic.h:638
>>>>>>  do_IRQ+0x15e/0x1a0 arch/x86/kernel/irq.c:263
>>>>>>  common_interrupt+0x86/0x86
>>>>>> ...
>>>>>>  </IRQ>
>>>>>>  arch_cpu_idle+0x20/0x30 arch/x86/kernel/process.c:332
>>>>>>  default_idle_call kernel/sched/idle.c:98
>>>>>>  cpuidle_idle_call kernel/sched/idle.c:156
>>>>>>  do_idle+0x334/0x730 kernel/sched/idle.c:246
>>>>>>  cpu_startup_entry+0x35/0x40 kernel/sched/idle.c:351
>>>>>>  rest_init+0xb8/0xc0 init/main.c:437
>>>>>>  start_kernel+0x4d7/0x530 init/main.c:703
>>>>>>  x86_64_start_reservations arch/x86/kernel/head64.c:318
>>>>>>  x86_64_start_kernel+0x3cd/0x3e0 arch/x86/kernel/head64.c:299
>>>>>>  secondary_startup_64+0x9f/0x9f arch/x86/kernel/head_64.S:219
>>>>>> origin:
>>>>>>  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
>>>>>>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:302
>>>>>>  kmsan_internal_poison_shadow+0xb3/0x1b0 mm/kmsan/kmsan.c:198
>>>>>>  kmsan_kmalloc+0x80/0xe0 mm/kmsan/kmsan.c:337
>>>>>>  kmem_cache_alloc+0x1e2/0x220 mm/slub.c:2756
>>>>>>  reqsk_alloc ./include/net/request_sock.h:88
>>>>>>  inet_reqsk_alloc+0xb8/0x6b0 net/ipv4/tcp_input.c:6231
>>>>>>  tcp_conn_request+0x89d/0x36f0 net/ipv4/tcp_input.c:6330
>>>>>>  tcp_v4_conn_request+0x16d/0x220 net/ipv4/tcp_ipv4.c:1314
>>>>>>  tcp_rcv_state_process+0x42a/0x7210 net/ipv4/tcp_input.c:5917
>>>>>>  tcp_v4_do_rcv+0xa6a/0xcd0 net/ipv4/tcp_ipv4.c:1483
>>>>>>  tcp_v4_rcv+0x3de0/0x4ab0 net/ipv4/tcp_ipv4.c:1763
>>>>>>  ip_local_deliver_finish+0x6bb/0xcb0 net/ipv4/ip_input.c:216
>>>>>>  NF_HOOK ./include/linux/netfilter.h:248
>>>>>> ...
>>>>>> ==================================================================
>>>>>>
>>>>>> --
>>>>>> Alexander Potapenko
>>>>>> Software Engineer
>>>>>>
>>>>>> Google Germany GmbH
>>>>>> Erika-Mann-Straße, 33
>>>>>> 80636 München
>>>>>>
>>>>>> Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
>>>>>> Registergericht und -nummer: Hamburg, HRB 86891
>>>>>> Sitz der Gesellschaft: Hamburg
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Alexander Potapenko
>>>>> Software Engineer
>>>>>
>>>>> Google Germany GmbH
>>>>> Erika-Mann-Straße, 33
>>>>> 80636 München
>>>>>
>>>>> Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
>>>>> Registergericht und -nummer: Hamburg, HRB 86891
>>>>> Sitz der Gesellschaft: Hamburg
>>
>>
>>
>> --
>> Alexander Potapenko
>> Software Engineer
>>
>> Google Germany GmbH
>> Erika-Mann-Straße, 33
>> 80636 München
>>
>> Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
>> Registergericht und -nummer: Hamburg, HRB 86891
>> Sitz der Gesellschaft: Hamburg
>
>
>
> --
> Alexander Potapenko
> Software Engineer
>
> Google Germany GmbH
> Erika-Mann-Straße, 33
> 80636 München
>
> Geschäftsführer: Paul Manicle, Halimah DeLaine Prado
> Registergericht und -nummer: Hamburg, HRB 86891
> Sitz der Gesellschaft: Hamburg

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