KASAN: slab-out-of-bounds Read in sctp_send_reset_streams

Hello,

syzkaller hit the following crash on  
328b4ed93b69a6f2083d52f31a240a09e5de386a
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


==================================================================
BUG: KASAN: slab-out-of-bounds in sctp_send_reset_streams+0xadf/0xc10  
net/sctp/stream.c:314
Read of size 2 at addr ffff8801d8a6c048 by task syzkaller104411/3085

CPU: 0 PID: 3085 Comm: syzkaller104411 Not tainted 4.15.0-rc2+ #119
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_load2_noabort+0x14/0x20 mm/kasan/report.c:428
  sctp_send_reset_streams+0xadf/0xc10 net/sctp/stream.c:314
  sctp_setsockopt_reset_streams net/sctp/socket.c:3905 [inline]
  sctp_setsockopt+0x70d/0x5d50 net/sctp/socket.c:4195
  compat_sock_common_setsockopt+0x104/0x140 net/core/sock.c:2981
  C_SYSC_setsockopt net/compat.c:403 [inline]
  compat_SyS_setsockopt+0x17c/0x410 net/compat.c:386
  do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
  do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125
RIP: 0023:0xf7f1bc79
RSP: 002b:00000000ff9893bc EFLAGS: 00000282 ORIG_RAX: 000000000000016e
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000000084
RDX: 0000000000000077 RSI: 000000002018b000 RDI: 0000000000000008
RBP: 000000000000001c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3085:
  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
  __do_kmalloc mm/slab.c:3711 [inline]
  __kmalloc_track_caller+0x15e/0x760 mm/slab.c:3726
  memdup_user+0x2c/0x90 mm/util.c:164
  sctp_setsockopt_reset_streams net/sctp/socket.c:3897 [inline]
  sctp_setsockopt+0x6a6/0x5d50 net/sctp/socket.c:4195
  compat_sock_common_setsockopt+0x104/0x140 net/core/sock.c:2981
  C_SYSC_setsockopt net/compat.c:403 [inline]
  compat_SyS_setsockopt+0x17c/0x410 net/compat.c:386
  do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
  do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:125

Freed by task 16:
  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:3491 [inline]
  kfree+0xca/0x250 mm/slab.c:3806
  selinux_cred_free+0x48/0x70 security/selinux/hooks.c:3814
  security_cred_free+0x48/0x80 security/security.c:995
  put_cred_rcu+0x106/0x400 kernel/cred.c:117
  __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
  rcu_do_batch kernel/rcu/tree.c:2758 [inline]
  invoke_rcu_callbacks kernel/rcu/tree.c:3012 [inline]
  __rcu_process_callbacks kernel/rcu/tree.c:2979 [inline]
  rcu_process_callbacks+0xd74/0x17d0 kernel/rcu/tree.c:2996
  __do_softirq+0x29d/0xbb2 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801d8a6c040
  which belongs to the cache kmalloc-32 of size 32
The buggy address is located 8 bytes inside of
  32-byte region [ffff8801d8a6c040, ffff8801d8a6c060)
The buggy address belongs to the page:
page:000000006b05592a count:1 mapcount:0 mapping:000000001ca7267d  
index:0xffff8801d8a6cfc1
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d8a6c000 ffff8801d8a6cfc1 000000010000003f
raw: ffffea000762f920 ffffea00076133e0 ffff8801db0001c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d8a6bf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d8a6bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc

ffff8801d8a6c000: fb fb fb fb fc fc fc fc 00 fc fc fc fc fc fc fc

                                               ^
  ffff8801d8a6c080: fb fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
  ffff8801d8a6c100: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================


---
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