Subject: KASAN: use-after-free Read in refcount_inc_not_zero

From: syzbot <[email-masked]>
Date: Thu, 02 Nov 2017 10:35:01 -0700

Hello,

syzkaller hit the following crash on  
73d3393ada4f70fa3df5639c8d438f2f034c0ecb
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.

netlink: 1 bytes leftover after parsing attributes in process  
`syz-executor4'.
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:276  
[inline]
BUG: KASAN: use-after-free in atomic_read arch/x86/include/asm/atomic.h:26  
[inline]
BUG: KASAN: use-after-free in refcount_inc_not_zero+0x16e/0x180  
lib/refcount.c:119
Read of size 4 at addr ffff8801c9de8ad8 by task syz-executor6/8757

CPU: 0 PID: 8757 Comm: syz-executor6 Not tainted 4.14.0-rc5+ #138
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:16 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:52
  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
  __read_once_size include/linux/compiler.h:276 [inline]
  atomic_read arch/x86/include/asm/atomic.h:26 [inline]
  refcount_inc_not_zero+0x16e/0x180 lib/refcount.c:119
  refcount_inc+0x15/0x50 lib/refcount.c:152
  sctp_association_hold+0x16/0x20 net/sctp/associola.c:875
  sctp_generate_timeout_event+0x2b0/0x330 net/sctp/sm_sideeffect.c:297
  sctp_generate_t1_init_event+0x1a/0x20 net/sctp/sm_sideeffect.c:330
  call_timer_fn+0x233/0x830 kernel/time/timer.c:1281
  expire_timers kernel/time/timer.c:1320 [inline]
  __run_timers+0x7fd/0xb90 kernel/time/timer.c:1620
  run_timer_softirq+0x4c/0xb0 kernel/time/timer.c:1646
  __do_softirq+0x2d7/0xb85 kernel/softirq.c:284
  invoke_softirq kernel/softirq.c:364 [inline]
  irq_exit+0x1cc/0x200 kernel/softirq.c:405
  exiting_irq arch/x86/include/asm/apic.h:638 [inline]
  smp_apic_timer_interrupt+0x177/0x710 arch/x86/kernel/apic/apic.c:1059
  apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:770
  </IRQ>
RIP: 0010:copy_page+0x7/0x10 arch/x86/lib/copy_page_64.S:17
RSP: 0018:ffff8801d2656e48 EFLAGS: 00010286 ORIG_RAX: ffffffffffffff10
RAX: ffff8801905c0100 RBX: 0000000006290080 RCX: 0000000000000140
RDX: 0000000000000000 RSI: ffff88018a402600 RDI: ffff880172c02600
RBP: ffff8801d2656f98 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000002
R13: ffff880000000000 R14: dffffc0000000000 R15: ffffffffffa20000
  migrate_page+0x149/0x1f0 mm/migrate.c:751
  move_to_new_page+0x3e1/0x8c0 mm/migrate.c:916
  __unmap_and_move+0xad2/0x1190 mm/migrate.c:1087
  unmap_and_move mm/migrate.c:1170 [inline]
  migrate_pages+0x956/0x2610 mm/migrate.c:1404
  do_mbind+0xa98/0xce0 mm/mempolicy.c:1239
  SYSC_mbind mm/mempolicy.c:1341 [inline]
  SyS_mbind+0x13b/0x150 mm/mempolicy.c:1323
  entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x452719
RSP: 002b:00007f37fadc7be8 EFLAGS: 00000212 ORIG_RAX: 00000000000000ed
RAX: ffffffffffffffda RBX: 00000000007580d8 RCX: 0000000000452719
RDX: 0000000000000000 RSI: 0000000000800000 RDI: 00000000203b5000
RBP: 0000000000000082 R08: 0000000000000001 R09: 0000000000000002
R10: 0000000020001ff8 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a6f7ff R14: 00007f37fadc89c0 R15: 0000000000000011

Allocated by task 8763:
  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
  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
  kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3627
  kmalloc include/linux/slab.h:493 [inline]
  kzalloc include/linux/slab.h:666 [inline]
  sctp_association_new+0x114/0x21e0 net/sctp/associola.c:309
  sctp_sendmsg+0x128c/0x31f0 net/sctp/socket.c:1838
  inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:762
  sock_sendmsg_nosec net/socket.c:633 [inline]
  sock_sendmsg+0xca/0x110 net/socket.c:643
  SYSC_sendto+0x352/0x5a0 net/socket.c:1750
  SyS_sendto+0x40/0x50 net/socket.c:1718
  entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 8776:
  save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
  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:3503 [inline]
  kfree+0xca/0x250 mm/slab.c:3820
  sctp_association_destroy net/sctp/associola.c:435 [inline]
  sctp_association_put+0x21c/0x2f0 net/sctp/associola.c:884
  sctp_association_free+0x688/0x930 net/sctp/associola.c:413
  sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:919 [inline]
  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1333 [inline]
  sctp_side_effects net/sctp/sm_sideeffect.c:1200 [inline]
  sctp_do_sm+0x28e7/0x6dd0 net/sctp/sm_sideeffect.c:1171
  sctp_primitive_SHUTDOWN+0xa0/0xd0 net/sctp/primitive.c:104
  sctp_close+0x3c6/0x980 net/sctp/socket.c:1532
  inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
  inet6_release+0x50/0x70 net/ipv6/af_inet6.c:433
  sock_release+0x8d/0x1e0 net/socket.c:597
  sock_close+0x16/0x20 net/socket.c:1126
  __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:112
  exit_task_work include/linux/task_work.h:21 [inline]
  do_exit+0x9b5/0x1ad0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16d0 kernel/signal.c:2334
  do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:808
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
  syscall_return_slowpath+0x42f/0x510 arch/x86/entry/common.c:266
  entry_SYSCALL_64_fastpath+0xbc/0xbe

The buggy address belongs to the object at ffff8801c9de8ac0
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 24 bytes inside of
  4096-byte region [ffff8801c9de8ac0, ffff8801c9de9ac0)
The buggy address belongs to the page:
page:ffffea0007277a00 count:1 mapcount:0 mapping:ffff8801c9de8ac0 index:0x0  
compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801c9de8ac0 0000000000000000 0000000100000001
raw: ffffea000727c9a0 ffffea0007290d20 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c9de8980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801c9de8a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801c9de8a80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                     ^
  ffff8801c9de8b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801c9de8b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
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Please credit me with: Reported-by: syzbot <[email-masked]>

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