Date:   Thu, 11 Jan 2018 17:30:17 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     syzbot <syzbot+7b7b518b1228d2743963@...kaller.appspotmail.com>
Cc:     davem <davem@...emloft.net>, LKML <linux-kernel@...r.kernel.org>,
        linux-sctp@...r.kernel.org, network dev <netdev@...r.kernel.org>,
        Neil Horman <nhorman@...driver.com>,
        syzkaller-bugs@...glegroups.com,
        Vlad Yasevich <vyasevich@...il.com>
Subject: Re: general protection fault in sctp_v6_get_dst

On Thu, Jan 11, 2018 at 2:15 AM, syzbot
<syzbot+7b7b518b1228d2743963@...kaller.appspotmail.com> wrote:
> syzkaller has found reproducer for the following crash on
> 61ad64080e039dce99a7f8d89b729bbea995e2f7
> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7b7b518b1228d2743963@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed.
>
> device lo entered promiscuous mode
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 3506 Comm: syzkaller968983 Not tainted 4.15.0-rc7+ #181
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:__read_once_size include/linux/compiler.h:183 [inline]
> RIP: 0010:sctp_v6_get_dst+0x59e/0x1c60 net/sctp/ipv6.c:271
> RSP: 0018:ffff8801db205e20 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8512e05b
> RDX: 000000000000000f RSI: 0000000067cf608c RDI: ffff8801db22376c
> RBP: ffff8801db206190 R08: 1ffff1003b640b05 R09: 0000000000000002
> R10: ffff8801db205cf0 R11: ffffffff8512e008 R12: ffff8801bf884db0
> R13: 000000000000204e R14: ffff8801bfe3e680 R15: ffff8801bf884d80
> FS:  00007f122e219700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020aaff09 CR3: 00000001bfdf0005 CR4: 00000000001606f0
>
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <IRQ>
>  sctp_transport_route+0xa8/0x430 net/sctp/transport.c:293
>  sctp_assoc_add_peer+0x4fe/0x1190 net/sctp/associola.c:655
>  sctp_process_init+0x119/0x2440 net/sctp/sm_make_chunk.c:2341
>  sctp_sf_do_5_1B_init+0x8c9/0xe80 net/sctp/sm_statefuns.c:414
>  sctp_do_sm+0x192/0x6ed0 net/sctp/sm_sideeffect.c:1178
>  sctp_endpoint_bh_rcv+0x379/0x8f0 net/sctp/endpointola.c:456
>  sctp_inq_push+0x23b/0x300 net/sctp/inqueue.c:95
>  sctp_rcv+0x29f3/0x35c0 net/sctp/input.c:267
>  sctp6_rcv+0x15/0x30 net/sctp/ipv6.c:1006
>  ip6_input_finish+0x37e/0x17a0 net/ipv6/ip6_input.c:284
>  NF_HOOK include/linux/netfilter.h:288 [inline]
>  ip6_input+0xdb/0x560 net/ipv6/ip6_input.c:327
>  dst_input include/net/dst.h:449 [inline]
>  ip6_rcv_finish+0x1a9/0x7a0 net/ipv6/ip6_input.c:71
>  NF_HOOK include/linux/netfilter.h:288 [inline]
>  ipv6_rcv+0xf37/0x1fa0 net/ipv6/ip6_input.c:208
>  __netif_receive_skb_core+0x1a41/0x3460 net/core/dev.c:4538
>  __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4603
>  process_backlog+0x203/0x740 net/core/dev.c:5283
>  napi_poll net/core/dev.c:5681 [inline]
>  net_rx_action+0x792/0x1910 net/core/dev.c:5747
>  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
>  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1133
>  </IRQ>
>  do_softirq.part.21+0x14d/0x190 kernel/softirq.c:329
>  do_softirq kernel/softirq.c:177 [inline]
>  __local_bh_enable_ip+0x1ee/0x230 kernel/softirq.c:182
>  local_bh_enable include/linux/bottom_half.h:32 [inline]
>  rcu_read_unlock_bh include/linux/rcupdate.h:727 [inline]
>  ip6_finish_output2+0xba0/0x23a0 net/ipv6/ip6_output.c:121
>  ip6_finish_output+0x698/0xaf0 net/ipv6/ip6_output.c:154
>  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
>  ip6_output+0x1eb/0x840 net/ipv6/ip6_output.c:171
>  dst_output include/net/dst.h:443 [inline]
>  NF_HOOK include/linux/netfilter.h:288 [inline]
>  ip6_xmit+0xd84/0x2090 net/ipv6/ip6_output.c:277
>  sctp_v6_xmit+0x438/0x630 net/sctp/ipv6.c:225
>  sctp_packet_transmit+0x225e/0x3750 net/sctp/output.c:638
>  sctp_outq_flush+0xabb/0x4060 net/sctp/outqueue.c:911
>  sctp_outq_uncork+0x5a/0x70 net/sctp/outqueue.c:776
>  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1807 [inline]
>  sctp_side_effects net/sctp/sm_sideeffect.c:1210 [inline]
>  sctp_do_sm+0x4e0/0x6ed0 net/sctp/sm_sideeffect.c:1181
>  sctp_primitive_ASSOCIATE+0x9d/0xd0 net/sctp/primitive.c:88
>  sctp_sendmsg+0x1d2e/0x33f0 net/sctp/socket.c:2018
>  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:764
>  sock_sendmsg_nosec net/socket.c:628 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:638
>  SYSC_sendto+0x361/0x5c0 net/socket.c:1719
>  SyS_sendto+0x40/0x50 net/socket.c:1687
>  entry_SYSCALL_64_fastpath+0x23/0x9a
> RIP: 0033:0x4456c9
> RSP: 002b:00007f122e218d98 EFLAGS: 00000212 ORIG_RAX: 000000000000002c
> RAX: ffffffffffffffda RBX: 00000000006dac3c RCX: 00000000004456c9
> RDX: 0000000000000001 RSI: 0000000020aaff09 RDI: 0000000000000007
> RBP: 0000000000000000 R08: 0000000020abf000 R09: 000000000000001c
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006dac38
> R13: 0000800000000001 R14: 0100000000000000 R15: 0000000000000008
> Code: 10 00 00 e8 e5 3d 5d fc 48 8b 85 e8 fc ff ff 48 83 c0 78 48 89 c2 48
> 89 85 c0 fc ff ff 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f
> 85 e9 15 00 00 48 8b 85 e8 fc ff ff 4c 8d b5 30
> RIP: __read_once_size include/linux/compiler.h:183 [inline] RSP:
> ffff8801db205e20
> RIP: sctp_v6_get_dst+0x59e/0x1c60 net/sctp/ipv6.c:271 RSP: ffff8801db205e20
> ---[ end trace 63ac71b302800ef4 ]---
>
v4 socket shouldn't have been allowed to bind v6 address, even it's v4mapped.

index de1087d..3595097 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -353,15 +353,14 @@ static struct sctp_af *sctp_sockaddr_af(struct
sctp_sock *opt,
        if (len < sizeof (struct sockaddr))
                return NULL;

+       if (!opt->pf->af_supported(addr->sa.sa_family, opt))
+               return NULL;
+
        /* V4 mapped address are really of AF_INET family */
        if (addr->sa.sa_family == AF_INET6 &&
            ipv6_addr_v4mapped(&addr->v6.sin6_addr)) {
                if (!opt->pf->af_supported(AF_INET, opt))
                        return NULL;
-       } else {
-               /* Does this PF support this AF? */
-               if (!opt->pf->af_supported(addr->sa.sa_family, opt))
-                       return NULL;
        }

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