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

From: syzbot <[email-masked]>
Date: Tue, 08 May 2018 06:58:02 -0700

Hello,

syzbot found the following crash on:

HEAD commit:    f142f08bf7ec Fix typo in comment.
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1159ade7800000
kernel config:  https://syzkaller.appspot.com/x/.config?x=31f4b3733894ef79
dashboard link: https://syzkaller.appspot.com/bug?extid=141d898c5f24489db4aa
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]

RDX: 0000000000000008 RSI: 0000000020000000 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000015
R13: 000000000000071e R14: 00000000006feb70 R15: 0000000000000007
==================================================================
BUG: KASAN: use-after-free in sctp_cmd_interpreter  
net/sctp/sm_sideeffect.c:1817 [inline]
BUG: KASAN: use-after-free in sctp_side_effects  
net/sctp/sm_sideeffect.c:1220 [inline]
BUG: KASAN: use-after-free in sctp_do_sm+0x6015/0x7160  
net/sctp/sm_sideeffect.c:1191
Read of size 1 at addr ffff8801c7883cb8 by task syz-executor6/18616

CPU: 1 PID: 18616 Comm: syz-executor6 Not tainted 4.17.0-rc4+ #38
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+0x1b9/0x294 lib/dump_stack.c:113
  print_address_description+0x6c/0x20b mm/kasan/report.c:256
  kasan_report_error mm/kasan/report.c:354 [inline]
  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1817 [inline]
  sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline]
  sctp_do_sm+0x6015/0x7160 net/sctp/sm_sideeffect.c:1191
  sctp_assoc_bh_rcv+0x30f/0x520 net/sctp/associola.c:1065
  sctp_inq_push+0x263/0x320 net/sctp/inqueue.c:95
  sctp_backlog_rcv+0x192/0xc00 net/sctp/input.c:350
  sk_backlog_rcv include/net/sock.h:909 [inline]
  __release_sock+0x12f/0x3a0 net/core/sock.c:2335
  release_sock+0xa4/0x2b0 net/core/sock.c:2850
  sctp_sendmsg+0x13cc/0x1d70 net/sctp/socket.c:2128
  inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:639
  sock_write_iter+0x35a/0x5a0 net/socket.c:908
  call_write_iter include/linux/fs.h:1784 [inline]
  new_sync_write fs/read_write.c:474 [inline]
  __vfs_write+0x64d/0x960 fs/read_write.c:487
  vfs_write+0x1f8/0x560 fs/read_write.c:549
  ksys_write+0xf9/0x250 fs/read_write.c:598
  __do_sys_write fs/read_write.c:610 [inline]
  __se_sys_write fs/read_write.c:607 [inline]
  __x64_sys_write+0x73/0xb0 fs/read_write.c:607
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455979
RSP: 002b:00007f6fad842c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f6fad8436d4 RCX: 0000000000455979
RDX: 0000000000000008 RSI: 0000000020000000 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000015
R13: 000000000000071e R14: 00000000006feb70 R15: 0000000000000007

Allocated by task 18616:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
  kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
  kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
  kmem_cache_zalloc include/linux/slab.h:691 [inline]
  sctp_chunkify+0xce/0x400 net/sctp/sm_make_chunk.c:1355
  sctp_rcv+0xc65/0x3a60 net/sctp/input.c:221
  sctp6_rcv+0x15/0x30 net/sctp/ipv6.c:1045
  ip6_input_finish+0x3ff/0x1a30 net/ipv6/ip6_input.c:284
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ip6_input+0xe1/0x5e0 net/ipv6/ip6_input.c:327
  dst_input include/net/dst.h:450 [inline]
  ip6_rcv_finish+0x29c/0xa10 net/ipv6/ip6_input.c:71
  NF_HOOK include/linux/netfilter.h:288 [inline]
  ipv6_rcv+0xed6/0x22a0 net/ipv6/ip6_input.c:208
  __netif_receive_skb_core+0x26f5/0x3630 net/core/dev.c:4592
  __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:4657
  process_backlog+0x219/0x760 net/core/dev.c:5337
  napi_poll net/core/dev.c:5735 [inline]
  net_rx_action+0x7b7/0x1930 net/core/dev.c:5801
  __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285

Freed by task 18616:
  save_stack+0x43/0xd0 mm/kasan/kasan.c:448
  set_track mm/kasan/kasan.c:460 [inline]
  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
  __cache_free mm/slab.c:3498 [inline]
  kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
  sctp_chunk_destroy net/sctp/sm_make_chunk.c:1481 [inline]
  sctp_chunk_put+0x321/0x440 net/sctp/sm_make_chunk.c:1504
  sctp_ulpevent_make_rcvmsg+0x955/0xd40 net/sctp/ulpevent.c:718
  sctp_ulpq_tail_data+0xa8/0x12b0 net/sctp/ulpqueue.c:108
  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1478 [inline]
  sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline]
  sctp_do_sm+0x1658/0x7160 net/sctp/sm_sideeffect.c:1191
  sctp_assoc_bh_rcv+0x30f/0x520 net/sctp/associola.c:1065
  sctp_inq_push+0x263/0x320 net/sctp/inqueue.c:95
  sctp_backlog_rcv+0x192/0xc00 net/sctp/input.c:350
  sk_backlog_rcv include/net/sock.h:909 [inline]
  __release_sock+0x12f/0x3a0 net/core/sock.c:2335
  release_sock+0xa4/0x2b0 net/core/sock.c:2850
  sctp_sendmsg+0x13cc/0x1d70 net/sctp/socket.c:2128
  inet_sendmsg+0x19f/0x690 net/ipv4/af_inet.c:798
  sock_sendmsg_nosec net/socket.c:629 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:639
  sock_write_iter+0x35a/0x5a0 net/socket.c:908
  call_write_iter include/linux/fs.h:1784 [inline]
  new_sync_write fs/read_write.c:474 [inline]
  __vfs_write+0x64d/0x960 fs/read_write.c:487
  vfs_write+0x1f8/0x560 fs/read_write.c:549
  ksys_write+0xf9/0x250 fs/read_write.c:598
  __do_sys_write fs/read_write.c:610 [inline]
  __se_sys_write fs/read_write.c:607 [inline]
  __x64_sys_write+0x73/0xb0 fs/read_write.c:607
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801c7883bc0
  which belongs to the cache sctp_chunk of size 256
The buggy address is located 248 bytes inside of
  256-byte region [ffff8801c7883bc0, ffff8801c7883cc0)
The buggy address belongs to the page:
page:ffffea00071e20c0 count:1 mapcount:0 mapping:ffff8801c7883080 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801c7883080 0000000000000000 000000010000000c
raw: ffffea000723a220 ffff8801cdb66f48 ffff8801cdb65600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8801c7883b80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
  ffff8801c7883c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801c7883c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
                                         ^
  ffff8801c7883d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8801c7883d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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