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

From: syzbot <[email-masked]>
Date: Wed, 01 Nov 2017 10:55:01 -0700

Hello,

syzkaller hit the following crash on  
25a5d23b47994cdb451dcd2bc8ac310a1492f71b
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: use-after-free in sctp_association_free+0x7b7/0x930  
net/sctp/associola.c:333
Read of size 8 at addr ffff8801d21d4720 by task syzkaller504854/3007

CPU: 0 PID: 3007 Comm: syzkaller504854 Not tainted 4.14.0-rc6+ #62
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __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_load8_noabort+0x14/0x20 mm/kasan/report.c:430
  sctp_association_free+0x7b7/0x930 net/sctp/associola.c:333
  sctp_sendmsg+0x2311/0x31f0 net/sctp/socket.c:2011
  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
  do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
  do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124
RIP: 0023:0xf7fd2c79
RSP: 002b:00000000f5fca1ec EFLAGS: 00000292 ORIG_RAX: 0000000000000171
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020925000
RDX: 0000000000000002 RSI: 0000000000000000 RDI: 00000000209e1000
RBP: 000000000000001c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3007:
  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
  do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
  do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124

Freed by task 3007:
  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_wait_for_sndbuf+0x5e3/0x7c0 net/sctp/socket.c:7836
  sctp_sendmsg+0x2750/0x31f0 net/sctp/socket.c:1935
  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
  do_syscall_32_irqs_on arch/x86/entry/common.c:329 [inline]
  do_fast_syscall_32+0x3f2/0xf05 arch/x86/entry/common.c:391
  entry_SYSENTER_compat+0x51/0x60 arch/x86/entry/entry_64_compat.S:124

The buggy address belongs to the object at ffff8801d21d4700
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 32 bytes inside of
  4096-byte region [ffff8801d21d4700, ffff8801d21d5700)
The buggy address belongs to the page:
page:ffffea0007487500 count:1 mapcount:0 mapping:ffff8801d21d4700 index:0x0  
compound_mapcount: 0
flags: 0x200000000008100(slab|head)
raw: 0200000000008100 ffff8801d21d4700 0000000000000000 0000000100000001
raw: ffffea0007487420 ffff8801dac01a48 ffff8801dac00dc0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801d21d4600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8801d21d4680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801d21d4700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                ^
  ffff8801d21d4780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801d21d4800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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