linux-kernel - Re: [PATCH] sctp: fully initialize the IPv6 address in sctp_v6_to

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Date:   Tue, 25 Jul 2017 14:34:24 +1200
From:   Xin Long <lucien.xin@...il.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     Dmitriy Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>,
        Vladislav Yasevich <vyasevich@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-sctp@...r.kernel.org
Subject: Re: [PATCH] sctp: fully initialize the IPv6 address in sctp_v6_to_addr()

On Tue, Jul 25, 2017 at 4:27 AM, Alexander Potapenko <glider@...gle.com> wrote:
> On Wed, Jul 19, 2017 at 2:58 AM, Xin Long <lucien.xin@...il.com> wrote:
>> On Wed, Jul 19, 2017 at 3:02 AM, Alexander Potapenko <glider@...gle.com> wrote:
>>> On Tue, Jul 18, 2017 at 4:55 PM, Alexander Potapenko <glider@...gle.com> wrote:
>>>> KMSAN reported use of uninitialized sctp_addr->v4.sin_addr.s_addr and
>>>> sctp_addr->v6.sin6_scope_id in sctp_v6_cmp_addr() (see below).
>>>> Make sure all fields of an IPv6 address are initialized, which
>>>> guarantees that the IPv4 fields are also initialized.
>>> I'm assuming here that the IPv4 address is known to overlap with the
>>> IPv6 one and doesn't need separate initialization.
>>>
>>
>> Ok, addr->v6.sin6_scope_id = 0 will fix the call trace you posted here.
> Sorry for the delay, I somehow missed your question.
>> addr->v6.sin6_flowinfo = 0 is to fix uninitialized
>> sctp_addr->v4.sin_addr.s_addr,
>> I couldn't see how this happens, can you also post the call trace for
>> v4.sin_addr.s_addr ?
> Here it is:
This one is still sctp_addr->v6.sin6_scope_id stuff.
'addr->v6.sin6_flowinfo = 0' is not actually necessay here, since
the two addr's family both are AF_INET6 and sctp_v6_cmp_addr()
doesn't use it in this path.

But  it's fine, It may be good to initialize all members here.

Reviewed-by: Xin Long <lucien.xin@...il.com>

>
> ==================================================================
> BUG: KMSAN: use of uninitialized memory in
> sctp_v6_cmp_addr+0x8d4/0x9f0 net/sctp/ipv6.c:535
> CPU: 2 PID: 17306 Comm: syz-executor1 Not tainted 4.11.0-rc5+ #2944
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
>  dump_stack+0x172/0x1c0 lib/dump_stack.c:42
>  is_logbuf_locked mm/kmsan/kmsan.c:59 [inline]
>  kmsan_report+0x12a/0x180 mm/kmsan/kmsan.c:938
>  native_save_fl arch/x86/include/asm/irqflags.h:18 [inline]
>  arch_local_save_flags arch/x86/include/asm/irqflags.h:72 [inline]
>  arch_local_irq_save arch/x86/include/asm/irqflags.h:113 [inline]
>  __msan_warning_32+0x61/0xb0 mm/kmsan/kmsan_instr.c:467
>  sctp_v6_cmp_addr+0x8d4/0x9f0 net/sctp/ipv6.c:535
>  sctp_v6_get_dst+0x8c7/0x1630 net/sctp/ipv6.c:297
>  sctp_transport_route+0x101/0x570 net/sctp/transport.c:292
>  sctp_assoc_add_peer+0x66d/0x16f0 net/sctp/associola.c:651
>  sctp_sendmsg+0x35a5/0x4f90 net/sctp/socket.c:1871
>  inet_sendmsg+0x498/0x670 net/ipv4/af_inet.c:762
>  sock_sendmsg_nosec net/socket.c:633 [inline]
>  sock_sendmsg net/socket.c:643 [inline]
>  SYSC_sendto+0x608/0x710 net/socket.c:1696
>  SyS_sendto+0x8a/0xb0 net/socket.c:1664
>  entry_SYSCALL_64_fastpath+0x13/0x94
> RIP: 0033:0x44b479
> RSP: 002b:00007f28a5bb2c08 EFLAGS: 00000286 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 0000000020000000 RCX: 000000000044b479
> RDX: 0000000000000001 RSI: 0000000020036000 RDI: 0000000000000005
> RBP: 0000000000708000 R08: 00000000206e4000 R09: 000000000000001c
> R10: 0000000000000000 R11: 0000000000000286 R12: 00000000ffffffff
> R13: 0000000000003760 R14: 00000000006e5820 R15: 0000000000ff9000
> origin description: ----dst_saddr@...p_v6_get_dst
> local variable created at:
>  sctp_v6_get_dst+0x91/0x1630 net/sctp/ipv6.c:236
>  sctp_transport_route+0x101/0x570 net/sctp/transport.c:292
> ==================================================================
>
>
>> Thanks
>
>
>
> --
> Alexander Potapenko
> Software Engineer
>
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