Subject: KASAN: use-after-free Read in sctp_id2assoc

From: syzbot <[email-masked]>
Date: Thu, 04 Oct 2018 01:48:03 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    4e6d47206c32 tls: Add support for inplace records encryption
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13834b81400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e569aa5632ebd436
dashboard link: https://syzkaller.appspot.com/bug?extid=c7dd55d7aec49d48e49a
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

netlink: 'syz-executor1': attribute type 1 has an invalid length.
==================================================================
BUG: KASAN: use-after-free in sctp_id2assoc+0x3a7/0x3e0  
net/sctp/socket.c:276
Read of size 8 at addr ffff880195b3eb20 by task syz-executor2/15454

CPU: 1 PID: 15454 Comm: syz-executor2 Not tainted 4.19.0-rc5+ #242
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
  print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
  sctp_id2assoc+0x3a7/0x3e0 net/sctp/socket.c:276
  sctp_do_peeloff+0x88/0x530 net/sctp/socket.c:5327
  sctp_getsockopt_peeloff_common.isra.24+0xb5/0x2f0 net/sctp/socket.c:5376
  sctp_getsockopt_peeloff_flags net/sctp/socket.c:5452 [inline]
  sctp_getsockopt+0x17f1/0x7c78 net/sctp/socket.c:7474
  sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:2997
  __sys_getsockopt+0x1ad/0x390 net/socket.c:1939
  __do_sys_getsockopt net/socket.c:1950 [inline]
  __se_sys_getsockopt net/socket.c:1947 [inline]
  __x64_sys_getsockopt+0xbe/0x150 net/socket.c:1947
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457579
Code: 1d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f86d7f8bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000457579
RDX: 000000000000007a RSI: 0000000000000084 RDI: 0000000000000007
RBP: 000000000072c040 R08: 00000000200001c0 R09: 0000000000000000
R10: 0000000020000080 R11: 0000000000000246 R12: 00007f86d7f8c6d4
R13: 00000000004c79b8 R14: 00000000004cdb70 R15: 00000000ffffffff

Allocated by task 15404:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
  kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
  kmalloc include/linux/slab.h:513 [inline]
  kzalloc include/linux/slab.h:707 [inline]
  sctp_association_new+0x12b/0x22a0 net/sctp/associola.c:311
  __sctp_connect+0x6ad/0xda0 net/sctp/socket.c:1209
  __sctp_setsockopt_connectx+0x134/0x190 net/sctp/socket.c:1368
  sctp_setsockopt_connectx net/sctp/socket.c:1400 [inline]
  sctp_setsockopt+0x18e2/0x6da0 net/sctp/socket.c:4359
  sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3038
  __sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
  __do_sys_setsockopt net/socket.c:1913 [inline]
  __se_sys_setsockopt net/socket.c:1910 [inline]
  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 15404:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kfree+0xcf/0x230 mm/slab.c:3813
  sctp_association_destroy net/sctp/associola.c:437 [inline]
  sctp_association_put+0x264/0x350 net/sctp/associola.c:885
  sctp_wait_for_connect+0x444/0x640 net/sctp/socket.c:8677
  __sctp_connect+0xbb3/0xda0 net/sctp/socket.c:1260
  __sctp_setsockopt_connectx+0x134/0x190 net/sctp/socket.c:1368
  sctp_setsockopt_connectx net/sctp/socket.c:1400 [inline]
  sctp_setsockopt+0x18e2/0x6da0 net/sctp/socket.c:4359
  sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3038
  __sys_setsockopt+0x1ba/0x3c0 net/socket.c:1902
  __do_sys_setsockopt net/socket.c:1913 [inline]
  __se_sys_setsockopt net/socket.c:1910 [inline]
  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1910
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff880195b3eb00
  which belongs to the cache kmalloc-4096 of size 4096
The buggy address is located 32 bytes inside of
  4096-byte region [ffff880195b3eb00, ffff880195b3fb00)
The buggy address belongs to the page:
page:ffffea000656cf80 count:1 mapcount:0 mapping:ffff8801da800dc0 index:0x0  
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea0006e66188 ffffea00065b5d08 ffff8801da800dc0
raw: 0000000000000000 ffff880195b3eb00 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff880195b3ea00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff880195b3ea80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff880195b3eb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                ^
  ffff880195b3eb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff880195b3ec00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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