Date:   Wed, 22 Nov 2017 14:38:44 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     Eric Dumazet <edumazet@...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 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?
>>>
>>>>> 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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