Date:   Thu, 04 Jan 2018 04:43:01 -0800
From:   syzbot <syzbot+e6a2cea7e8fc44b2bf7c@...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: KASAN: use-after-free Read in ip_defrag

Hello,

syzkaller hit the following crash on  
6bb8824732f69de0f233ae6b1a8158e149627b38
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.
Unfortunately, I don't have any reproducer for this bug yet.


IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e6a2cea7e8fc44b2bf7c@...kaller.appspotmail.com
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.

==================================================================
BUG: KASAN: use-after-free in ip_frag_queue net/ipv4/ip_fragment.c:413  
[inline]
BUG: KASAN: use-after-free in ip_defrag+0x3d64/0x4140  
net/ipv4/ip_fragment.c:682
Read of size 4 at addr ffff8801d4131100 by task syz-executor2/13372

CPU: 1 PID: 13372 Comm: syz-executor2 Not tainted 4.15.0-rc5+ #170
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:252
  kasan_report_error mm/kasan/report.c:351 [inline]
  kasan_report+0x25b/0x340 mm/kasan/report.c:409
  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
  ip_frag_queue net/ipv4/ip_fragment.c:413 [inline]
  ip_defrag+0x3d64/0x4140 net/ipv4/ip_fragment.c:682
  ip_local_deliver+0x174/0x6e0 net/ipv4/ip_input.c:253
  dst_input include/net/dst.h:449 [inline]
  ip_rcv_finish+0x881/0x19a0 net/ipv4/ip_input.c:397
  NF_HOOK include/linux/netfilter.h:250 [inline]
  ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493
  __netif_receive_skb_core+0x1a3e/0x3450 net/core/dev.c:4499
  __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4564
  netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4638
  napi_frags_finish net/core/dev.c:5079 [inline]
  napi_gro_frags+0x57b/0xad0 net/core/dev.c:5152
  tun_get_user+0x271f/0x3900 drivers/net/tun.c:1791
  tun_chr_write_iter+0xb9/0x160 drivers/net/tun.c:1836
  call_write_iter include/linux/fs.h:1772 [inline]
  do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:653
  do_iter_write+0x154/0x540 fs/read_write.c:932
  vfs_writev+0x18a/0x340 fs/read_write.c:977
  do_writev+0xfc/0x2a0 fs/read_write.c:1012
  SYSC_writev fs/read_write.c:1085 [inline]
  SyS_writev+0x27/0x30 fs/read_write.c:1082
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x4529a1
RSP: 002b:00007fc69300cb80 EFLAGS: 00000293 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 0000000020b92000 RCX: 00000000004529a1
RDX: 0000000000000001 RSI: 00007fc69300cbd0 RDI: 0000000000000012
RBP: 0000000000000042 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000003f R11: 0000000000000293 R12: 00000000006f68a8
R13: 00000000ffffffff R14: 00007fc69300d6d4 R15: 0000000000000000

Allocated by task 3190:
  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
  skb_clone+0x1ae/0x480 net/core/skbuff.c:1279
  dev_queue_xmit_nit+0x40e/0xc40 net/core/dev.c:1948
  xmit_one net/core/dev.c:3004 [inline]
  dev_hard_start_xmit+0x16b/0xac0 net/core/dev.c:3024
  sch_direct_xmit+0x42b/0xe80 net/sched/sch_generic.c:314
  qdisc_restart net/sched/sch_generic.c:380 [inline]
  __qdisc_run+0x571/0x19b0 net/sched/sch_generic.c:388
  __dev_xmit_skb net/core/dev.c:3188 [inline]
  __dev_queue_xmit+0xb1f/0x2590 net/core/dev.c:3489
  dev_queue_xmit+0x17/0x20 net/core/dev.c:3554
  neigh_hh_output include/net/neighbour.h:472 [inline]
  neigh_output include/net/neighbour.h:480 [inline]
  ip_finish_output2+0xeed/0x14f0 net/ipv4/ip_output.c:229
  ip_finish_output+0x85e/0xd10 net/ipv4/ip_output.c:317
  NF_HOOK_COND include/linux/netfilter.h:239 [inline]
  ip_output+0x1cc/0x860 net/ipv4/ip_output.c:405
  dst_output include/net/dst.h:443 [inline]
  ip_local_out+0x95/0x160 net/ipv4/ip_output.c:124
  ip_queue_xmit+0x8c0/0x18e0 net/ipv4/ip_output.c:504
  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:2540
  tcp_push+0x538/0x770 net/ipv4/tcp.c:728
  tcp_sendmsg_locked+0x2870/0x3c40 net/ipv4/tcp.c:1428
  tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1465
  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
  sock_write_iter+0x31a/0x5d0 net/socket.c:907
  call_write_iter include/linux/fs.h:1772 [inline]
  new_sync_write fs/read_write.c:469 [inline]
  __vfs_write+0x684/0x970 fs/read_write.c:482
  vfs_write+0x189/0x510 fs/read_write.c:544
  SYSC_write fs/read_write.c:589 [inline]
  SyS_write+0xef/0x220 fs/read_write.c:581
  entry_SYSCALL_64_fastpath+0x1f/0x96

Freed by task 3190:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
  set_track mm/kasan/kasan.c:459 [inline]
  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
  __cache_free mm/slab.c:3488 [inline]
  kmem_cache_free+0x83/0x2a0 mm/slab.c:3746
  kfree_skbmem+0x1a1/0x1d0 net/core/skbuff.c:582
  __kfree_skb net/core/skbuff.c:642 [inline]
  kfree_skb+0x165/0x4c0 net/core/skbuff.c:659
  packet_rcv_spkt+0x117/0x5b0 net/packet/af_packet.c:1872
  dev_queue_xmit_nit+0x866/0xc40 net/core/dev.c:1980
  xmit_one net/core/dev.c:3004 [inline]
  dev_hard_start_xmit+0x16b/0xac0 net/core/dev.c:3024
  sch_direct_xmit+0x42b/0xe80 net/sched/sch_generic.c:314
  qdisc_restart net/sched/sch_generic.c:380 [inline]
  __qdisc_run+0x571/0x19b0 net/sched/sch_generic.c:388
  __dev_xmit_skb net/core/dev.c:3188 [inline]
  __dev_queue_xmit+0xb1f/0x2590 net/core/dev.c:3489
  dev_queue_xmit+0x17/0x20 net/core/dev.c:3554
  neigh_hh_output include/net/neighbour.h:472 [inline]
  neigh_output include/net/neighbour.h:480 [inline]
  ip_finish_output2+0xeed/0x14f0 net/ipv4/ip_output.c:229
  ip_finish_output+0x85e/0xd10 net/ipv4/ip_output.c:317
  NF_HOOK_COND include/linux/netfilter.h:239 [inline]
  ip_output+0x1cc/0x860 net/ipv4/ip_output.c:405
  dst_output include/net/dst.h:443 [inline]
  ip_local_out+0x95/0x160 net/ipv4/ip_output.c:124
  ip_queue_xmit+0x8c0/0x18e0 net/ipv4/ip_output.c:504
  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:2540
  tcp_push+0x538/0x770 net/ipv4/tcp.c:728
  tcp_sendmsg_locked+0x2870/0x3c40 net/ipv4/tcp.c:1428
  tcp_sendmsg+0x2f/0x50 net/ipv4/tcp.c:1465
  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
  sock_write_iter+0x31a/0x5d0 net/socket.c:907
  call_write_iter include/linux/fs.h:1772 [inline]
  new_sync_write fs/read_write.c:469 [inline]
  __vfs_write+0x684/0x970 fs/read_write.c:482
  vfs_write+0x189/0x510 fs/read_write.c:544
  SYSC_write fs/read_write.c:589 [inline]
  SyS_write+0xef/0x220 fs/read_write.c:581
  entry_SYSCALL_64_fastpath+0x1f/0x96

The buggy address belongs to the object at ffff8801d41310c0
  which belongs to the cache skbuff_head_cache of size 224
The buggy address is located 64 bytes inside of
  224-byte region [ffff8801d41310c0, ffff8801d41311a0)
The buggy address belongs to the page:
page:00000000f21301b4 count:1 mapcount:0 mapping:00000000324eb6c2 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d41310c0 0000000000000000 000000010000000c
raw: ffffea00073f69e0 ffffea000744efa0 ffff8801d986bcc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d4131000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d4131080: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff8801d4131100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                    ^
  ffff8801d4131180: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d4131200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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