Subject: KASAN: slab-out-of-bounds Write in tcp_v6_syn_recv_sock

From: syzbot <[email-masked]>
Date: Tue, 02 Jan 2018 15:58:01 -0800

Hello,

syzkaller hit the following crash on  
61233580f1f33c50e159c50e24d80ffd2ba2e06b
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.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: [email-masked]
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending  
cookies.  Check SNMP counters.
==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:344 [inline]
BUG: KASAN: slab-out-of-bounds in tcp_v6_syn_recv_sock+0x628/0x23a0  
net/ipv6/tcp_ipv6.c:1144
Write of size 160 at addr ffff8801cbdd7460 by task syzkaller545407/3196

CPU: 1 PID: 3196 Comm: syzkaller545407 Not tainted 4.15.0-rc5+ #241
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __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:252
  kasan_report_error mm/kasan/report.c:351 [inline]
  kasan_report+0x25b/0x340 mm/kasan/report.c:409
  check_memory_region_inline mm/kasan/kasan.c:260 [inline]
  check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
  memcpy+0x37/0x50 mm/kasan/kasan.c:303
  memcpy include/linux/string.h:344 [inline]
  tcp_v6_syn_recv_sock+0x628/0x23a0 net/ipv6/tcp_ipv6.c:1144
  tcp_get_cookie_sock+0x102/0x540 net/ipv4/syncookies.c:213
  cookie_v6_check+0x177d/0x2160 net/ipv6/syncookies.c:255
  tcp_v6_cookie_check net/ipv6/tcp_ipv6.c:1008 [inline]
  tcp_v6_do_rcv+0xe4d/0x11c0 net/ipv6/tcp_ipv6.c:1316
  tcp_v6_rcv+0x22ee/0x2b40 net/ipv6/tcp_ipv6.c:1510
  ip6_input_finish+0x36f/0x1700 net/ipv6/ip6_input.c:284
  NF_HOOK include/linux/netfilter.h:250 [inline]
  ip6_input+0xe9/0x560 net/ipv6/ip6_input.c:327
  dst_input include/net/dst.h:466 [inline]
  ip6_rcv_finish+0x1a9/0x7a0 net/ipv6/ip6_input.c:71
  NF_HOOK include/linux/netfilter.h:250 [inline]
  ipv6_rcv+0xf1f/0x1f80 net/ipv6/ip6_input.c:208
  __netif_receive_skb_core+0x1a3e/0x3450 net/core/dev.c:4461
  __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4526
  process_backlog+0x203/0x740 net/core/dev.c:5205
  napi_poll net/core/dev.c:5603 [inline]
  net_rx_action+0x792/0x1910 net/core/dev.c:5669
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285
  do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1115
  </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+0xba6/0x2390 net/ipv6/ip6_output.c:121
  ip6_finish_output+0x2f9/0x920 net/ipv6/ip6_output.c:146
  NF_HOOK_COND include/linux/netfilter.h:239 [inline]
  ip6_output+0x1eb/0x840 net/ipv6/ip6_output.c:163
  dst_output include/net/dst.h:460 [inline]
  NF_HOOK include/linux/netfilter.h:250 [inline]
  ip6_xmit+0xd75/0x2080 net/ipv6/ip6_output.c:269
  inet6_csk_xmit+0x2fc/0x580 net/ipv6/inet6_connection_sock.c:139
  tcp_transmit_skb+0x1b12/0x38b0 net/ipv4/tcp_output.c:1176
  tcp_write_xmit+0x680/0x5190 net/ipv4/tcp_output.c:2367
  __tcp_push_pending_frames+0xa0/0x250 net/ipv4/tcp_output.c:2543
  tcp_send_fin+0x1b0/0xd20 net/ipv4/tcp_output.c:3087
  tcp_close+0xbe0/0xfc0 net/ipv4/tcp.c:2234
  inet_release+0xed/0x1c0 net/ipv4/af_inet.c:426
  inet6_release+0x50/0x70 net/ipv6/af_inet6.c:432
  sock_release+0x8d/0x1e0 net/socket.c:600
  sock_close+0x16/0x20 net/socket.c:1129
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16c0 kernel/signal.c:2335
  do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
  entry_SYSCALL_64_fastpath+0x94/0x96
RIP: 0033:0x4456e9
RSP: 002b:00007fb4de631da8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006dac3c RCX: 00000000004456e9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006dac3c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac38
R13: 0100000000000000 R14: 00007fb4de6329c0 R15: 0000000000000009

Allocated by task 3196:
  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:551
  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3544
  sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1463
  sk_clone_lock+0x152/0x1570 net/core/sock.c:1649
  inet_csk_clone_lock+0x92/0x4f0 net/ipv4/inet_connection_sock.c:781
  tcp_create_openreq_child+0x9b/0x1b70 net/ipv4/tcp_minisocks.c:449
  tcp_v6_syn_recv_sock+0x22d/0x23a0 net/ipv6/tcp_ipv6.c:1123
  tcp_get_cookie_sock+0x102/0x540 net/ipv4/syncookies.c:213
  cookie_v6_check+0x177d/0x2160 net/ipv6/syncookies.c:255
  tcp_v6_cookie_check net/ipv6/tcp_ipv6.c:1008 [inline]
  tcp_v6_do_rcv+0xe4d/0x11c0 net/ipv6/tcp_ipv6.c:1316
  tcp_v6_rcv+0x22ee/0x2b40 net/ipv6/tcp_ipv6.c:1510
  ip6_input_finish+0x36f/0x1700 net/ipv6/ip6_input.c:284
  NF_HOOK include/linux/netfilter.h:250 [inline]
  ip6_input+0xe9/0x560 net/ipv6/ip6_input.c:327
  dst_input include/net/dst.h:466 [inline]
  ip6_rcv_finish+0x1a9/0x7a0 net/ipv6/ip6_input.c:71
  NF_HOOK include/linux/netfilter.h:250 [inline]
  ipv6_rcv+0xf1f/0x1f80 net/ipv6/ip6_input.c:208
  __netif_receive_skb_core+0x1a3e/0x3450 net/core/dev.c:4461
  __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4526
  process_backlog+0x203/0x740 net/core/dev.c:5205
  napi_poll net/core/dev.c:5603 [inline]
  net_rx_action+0x792/0x1910 net/core/dev.c:5669
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8801cbdd6a80
  which belongs to the cache TCP of size 2528
The buggy address is located 0 bytes to the right of
  2528-byte region [ffff8801cbdd6a80, ffff8801cbdd7460)
The buggy address belongs to the page:
page:000000006145927c count:1 mapcount:0 mapping:00000000d41dd7c1  
index:0xffff8801cbdd7ffd compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801cbdd6000 ffff8801cbdd7ffd 0000000100000003
raw: ffffea00074ef120 ffff8801d82b7248 ffff8801d798b640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801cbdd7300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff8801cbdd7380: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801cbdd7400: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
                                                        ^
  ffff8801cbdd7480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801cbdd7500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to [email-masked].

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is  
merged
into any tree, please reply to this email with:
#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
#syz test: git://repo/address.git branch
and provide the patch inline or as an attachment.
To mark this as a duplicate of another syzbot report, please reply with:
#syz dup: exact-subject-of-another-report
If it's a one-off invalid bug report, please reply with:
#syz invalid
Note: if the crash happens again, it will cause creation of a new bug  
report.
Note: all commands must start from beginning of the line in the email body.