------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 11437 at lib/refcount.c:28 refcount_warn_saturate+0x1dc/0x1f0 lib/refcount.c:28
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 11437 Comm: syz-executor.1 Not tainted 5.6.0-rc2-next-20200224-syzkaller #0
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+0x197/0x210 lib/dump_stack.c:118
 panic+0x2e3/0x75c kernel/panic.c:221
 __warn.cold+0x2f/0x3e kernel/panic.c:582
 report_bug+0x289/0x300 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:175 [inline]
 fixup_bug arch/x86/kernel/traps.c:170 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:refcount_warn_saturate+0x1dc/0x1f0 lib/refcount.c:28
Code: e9 d8 fe ff ff 48 89 df e8 11 73 10 fe e9 85 fe ff ff e8 47 45 d1 fd 48 c7 c7 40 cd 91 88 c6 05 81 96 fc 06 01 e8 63 65 a1 fd <0f> 0b e9 ac fe ff ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 55 48
RSP: 0018:ffffc90006e17720 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815ee766 RDI: fffff52000dc2ed6
RBP: ffffc90006e17730 R08: ffff888091c2c080 R09: ffffed1015d06661
R10: ffffed1015d06660 R11: ffff8880ae833307 R12: 0000000000000003
R13: ffff8880a24fca44 R14: 0000000000008100 R15: ffff888093bb3540
 refcount_sub_and_test include/linux/refcount.h:261 [inline]
 sock_wfree+0x1f8/0x260 net/core/sock.c:1973
 sctp_wfree+0x389/0x990 net/sctp/socket.c:9111
 skb_release_head_state+0xeb/0x260 net/core/skbuff.c:651
 skb_release_all+0x16/0x60 net/core/skbuff.c:662
 __kfree_skb net/core/skbuff.c:678 [inline]
 consume_skb net/core/skbuff.c:837 [inline]
 consume_skb+0xfb/0x410 net/core/skbuff.c:831
 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1454 [inline]
 sctp_chunk_put+0x1d4/0x2f0 net/sctp/sm_make_chunk.c:1481
 sctp_chunk_free+0x56/0x70 net/sctp/sm_make_chunk.c:1468
 __sctp_outq_teardown+0x71f/0xc60 net/sctp/outqueue.c:257
 sctp_outq_free+0x16/0x20 net/sctp/outqueue.c:277
 sctp_association_free+0x208/0x7e0 net/sctp/associola.c:339
 sctp_cmd_delete_tcb net/sctp/sm_sideeffect.c:930 [inline]
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1318 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1185 [inline]
 sctp_do_sm+0x3ba6/0x5340 net/sctp/sm_sideeffect.c:1156
 sctp_primitive_ABORT+0xa0/0xd0 net/sctp/primitive.c:104
 sctp_close+0x259/0x960 net/sctp/socket.c:1512
 inet_release+0xed/0x200 net/ipv4/af_inet.c:427
 __sock_release+0xce/0x280 net/socket.c:605
 sock_close+0x1e/0x30 net/socket.c:1283
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x676/0x790 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x415fe1
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffc6b4a0cc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000415fe1
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000001 R08: 000000006e71b375 R09: 000000006e71b379
R10: 00007ffc6b4a0da0 R11: 0000000000000293 R12: 000000000076bf20
R13: 00000000007708b0 R14: 000000000004ff0f R15: 000000000076bf2c
Kernel Offset: disabled
Rebooting in 86400 seconds..