Date:   Thu, 20 Sep 2018 13:54:04 -0700
From:   syzbot <syzbot+f08ac29f2ac8aea19826@...kaller.appspotmail.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, yoshfuji@...ux-ipv6.org
Subject: KMSAN: uninit-value in ip6_parse_tlv

Hello,

syzbot found the following crash on:

HEAD commit:    74ee2200b89f kmsan: bump .config.example to v4.17-rc3
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?x=1426fde7800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4ca1e57bafa8ab1f
dashboard link: https://syzkaller.appspot.com/bug?extid=f08ac29f2ac8aea19826
compiler:       clang version 7.0.0 (trunk 329391)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15574be7800000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1003fc37800000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f08ac29f2ac8aea19826@...kaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KMSAN: uninit-value in ip6_parse_tlv+0x8d5/0xcd0 net/ipv6/exthdrs.c:172
CPU: 1 PID: 4535 Comm: syz-executor786 Not tainted 4.17.0-rc3+ #88
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x185/0x1d0 lib/dump_stack.c:113
  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
  ip6_parse_tlv+0x8d5/0xcd0 net/ipv6/exthdrs.c:172
  ipv6_destopt_rcv+0x50d/0xd90 net/ipv6/exthdrs.c:310
  ip6_input_finish+0xaac/0x2250 net/ipv6/ip6_input.c:284
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ip6_input net/ipv6/ip6_input.c:327 [inline]
  ip6_mc_input+0xa67/0x1080 net/ipv6/ip6_input.c:404
  dst_input include/net/dst.h:450 [inline]
  ip6_rcv_finish+0x46e/0x6e0 net/ipv6/ip6_input.c:71
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ipv6_rcv+0x1e16/0x2340 net/ipv6/ip6_input.c:208
  __netif_receive_skb_core+0x47df/0x4a90 net/core/dev.c:4592
  __netif_receive_skb net/core/dev.c:4657 [inline]
  process_backlog+0x62d/0xe20 net/core/dev.c:5337
  napi_poll net/core/dev.c:5735 [inline]
  net_rx_action+0x7c1/0x1a70 net/core/dev.c:5801
  __do_softirq+0x56d/0x93d kernel/softirq.c:285
  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1046
  </IRQ>
  do_softirq+0xb6/0xf0 kernel/softirq.c:329
  netif_rx_ni net/core/dev.c:4219 [inline]
  dev_loopback_xmit+0x8b0/0x900 net/core/dev.c:3347
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ip6_finish_output2+0x1e24/0x2110 net/ipv6/ip6_output.c:84
  ip6_finish_output+0xae9/0xba0 net/ipv6/ip6_output.c:154
  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
  ip6_output+0x597/0x6c0 net/ipv6/ip6_output.c:171
  dst_output include/net/dst.h:444 [inline]
  ip6_local_out+0x15e/0x1d0 net/ipv6/output_core.c:176
  ip6_send_skb net/ipv6/ip6_output.c:1702 [inline]
  ip6_push_pending_frames+0x218/0x4d0 net/ipv6/ip6_output.c:1722
  rawv6_push_pending_frames net/ipv6/raw.c:616 [inline]
  rawv6_sendmsg+0x4235/0x4fb0 net/ipv6/raw.c:935
  inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg net/socket.c:639 [inline]
  __sys_sendto+0x6c0/0x7e0 net/socket.c:1789
  __do_sys_sendto net/socket.c:1801 [inline]
  __se_sys_sendto net/socket.c:1797 [inline]
  __x64_sys_sendto+0x1a1/0x210 net/socket.c:1797
  do_syscall_64+0x154/0x220 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x43fe79
RSP: 002b:00007ffc475970d8 EFLAGS: 00000216 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fe79
RDX: 0000000000000000 RSI: 0000000020001ffe RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000020003000 R09: 000000000000001c
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004017a0
R13: 0000000000401830 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
  kmsan_slab_alloc+0x10/0x20 mm/kmsan/kmsan.c:321
  slab_post_alloc_hook mm/slab.h:446 [inline]
  slab_alloc_node mm/slub.c:2753 [inline]
  __kmalloc_node_track_caller+0xb32/0x11b0 mm/slub.c:4395
  __kmalloc_reserve net/core/skbuff.c:138 [inline]
  __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
  alloc_skb include/linux/skbuff.h:988 [inline]
  alloc_skb_with_frags+0x1e6/0xb80 net/core/skbuff.c:5254
  sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2088
  sock_alloc_send_skb+0xca/0xe0 net/core/sock.c:2105
  __ip6_append_data+0x33a2/0x4e40 net/ipv6/ip6_output.c:1427
  ip6_append_data+0x40e/0x6b0 net/ipv6/ip6_output.c:1596
  rawv6_sendmsg+0x2740/0x4fb0 net/ipv6/raw.c:928
  inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg net/socket.c:639 [inline]
  __sys_sendto+0x6c0/0x7e0 net/socket.c:1789
  __do_sys_sendto net/socket.c:1801 [inline]
  __se_sys_sendto net/socket.c:1797 [inline]
  __x64_sys_sendto+0x1a1/0x210 net/socket.c:1797
  do_syscall_64+0x154/0x220 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x44/0xa9
==================================================================


---
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