KASAN: use-after-free Write in nf_nat_ipv6_manip_pkt

Hello,

syzbot hit the following crash on net-next commit
1ec010e705934c8acbe7dbf31afc81e60e3d828b (Fri Feb 16 10:03:07 2018 +0000)
tun: export flags, uid, gid, queue information over netlink

So far this crash happened 2 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+10005f4292fc9cc89de7@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: use-after-free in nf_nat_ipv6_manip_pkt+0x47c/0x490  
net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:106
Write of size 16 at addr ffff8801d551e0e0 by task syzkaller546592/4162

CPU: 0 PID: 4162 Comm: syzkaller546592 Not tainted 4.16.0-rc1+ #231
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  print_address_description+0x73/0x250 mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report+0x23b/0x360 mm/kasan/report.c:412
  __asan_report_store_n_noabort+0x12/0x14 mm/kasan/report.c:449
  nf_nat_ipv6_manip_pkt+0x47c/0x490  
net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:106
  nf_nat_packet+0x3cb/0x560 net/netfilter/nf_nat_core.c:506
  nf_nat_ipv6_fn+0x679/0xa80 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:329
  nf_nat_ipv6_local_fn+0x33/0x5d0  
net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:407
  ip6table_nat_local_fn+0x2c/0x40 net/ipv6/netfilter/ip6table_nat.c:69
  nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline]
  nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483
  nf_hook include/linux/netfilter.h:243 [inline]
  __ip6_local_out+0x517/0xaa0 net/ipv6/output_core.c:164
  ip6_local_out+0x2d/0x160 net/ipv6/output_core.c:174
  ip6_send_skb+0xa1/0x330 net/ipv6/ip6_output.c:1677
  ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1697
  rawv6_push_pending_frames net/ipv6/raw.c:616 [inline]
  rawv6_sendmsg+0x2f96/0x40c0 net/ipv6/raw.c:935
  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:639
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
  __sys_sendmsg+0xe5/0x210 net/socket.c:2081
  SYSC_sendmsg net/socket.c:2092 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2088
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x446ea9
RSP: 002b:00007ffc61680508 EFLAGS: 00000217 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000000003e RCX: 0000000000446ea9
RDX: 0000000000000000 RSI: 00000000209f2fc8 RDI: 0000000000000004
RBP: 00007ffc61680618 R08: 0000000000008a7f R09: 0000000000008a7f
R10: 0000000000000000 R11: 0000000000000217 R12: 00007ffc61680618
R13: 0000000000404370 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 4162:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
  __do_kmalloc_node mm/slab.c:3669 [inline]
  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3683
  __kmalloc_reserve.isra.39+0x41/0xd0 net/core/skbuff.c:137
  __alloc_skb+0x13b/0x780 net/core/skbuff.c:205
  alloc_skb include/linux/skbuff.h:986 [inline]
  sock_wmalloc+0x140/0x1d0 net/core/sock.c:1941
  __ip6_append_data.isra.44+0x26b9/0x3390 net/ipv6/ip6_output.c:1416
  ip6_append_data+0x189/0x290 net/ipv6/ip6_output.c:1571
  rawv6_sendmsg+0x1e09/0x40c0 net/ipv6/raw.c:928
  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:639
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
  __sys_sendmsg+0xe5/0x210 net/socket.c:2081
  SYSC_sendmsg net/socket.c:2092 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2088
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b

Freed by task 4162:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
  __cache_free mm/slab.c:3485 [inline]
  kfree+0xd9/0x260 mm/slab.c:3800
  skb_free_head+0x74/0xb0 net/core/skbuff.c:550
  pskb_expand_head+0x36b/0x1210 net/core/skbuff.c:1492
  __pskb_pull_tail+0x14a/0x17f0 net/core/skbuff.c:1875
  skb_make_writable+0x15b/0x750 net/netfilter/core.c:528
  tcp_manip_pkt+0x82/0x2d0 net/netfilter/nf_nat_proto_tcp.c:51
  nf_nat_ipv6_manip_pkt+0x22d/0x490  
net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:99
  nf_nat_packet+0x3cb/0x560 net/netfilter/nf_nat_core.c:506
  nf_nat_ipv6_fn+0x679/0xa80 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:329
  nf_nat_ipv6_local_fn+0x33/0x5d0  
net/ipv6/netfilter/nf_nat_l3proto_ipv6.c:407
  ip6table_nat_local_fn+0x2c/0x40 net/ipv6/netfilter/ip6table_nat.c:69
  nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline]
  nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483
  nf_hook include/linux/netfilter.h:243 [inline]
  __ip6_local_out+0x517/0xaa0 net/ipv6/output_core.c:164
  ip6_local_out+0x2d/0x160 net/ipv6/output_core.c:174
  ip6_send_skb+0xa1/0x330 net/ipv6/ip6_output.c:1677
  ip6_push_pending_frames+0xb3/0xe0 net/ipv6/ip6_output.c:1697
  rawv6_push_pending_frames net/ipv6/raw.c:616 [inline]
  rawv6_sendmsg+0x2f96/0x40c0 net/ipv6/raw.c:935
  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:763
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:639
  ___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
  __sys_sendmsg+0xe5/0x210 net/socket.c:2081
  SYSC_sendmsg net/socket.c:2092 [inline]
  SyS_sendmsg+0x2d/0x50 net/socket.c:2088
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b

The buggy address belongs to the object at ffff8801d551e040
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 160 bytes inside of
  512-byte region [ffff8801d551e040, ffff8801d551e240)
The buggy address belongs to the page:
page:ffffea0007554780 count:1 mapcount:0 mapping:ffff8801d551e040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d551e040 0000000000000000 0000000100000006
raw: ffffea00075763e0 ffffea00075571e0 ffff8801db000940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d551df80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d551e000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb

ffff8801d551e080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

                                                        ^
  ffff8801d551e100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801d551e180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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