------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 9425 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 9425 Comm: syz-executor764 Not tainted 5.6.0-rc3-next-20200228-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+0x188/0x20d lib/dump_stack.c:118
 panic+0x2e3/0x75c kernel/panic.c:221
 __warn.cold+0x2f/0x35 kernel/panic.c:582
 report_bug+0x27b/0x2f0 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+0x12b/0x220 arch/x86/kernel/traps.c:267
 do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
 invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Code: e9 db fe ff ff 48 89 df e8 1c e7 1f fe e9 8a fe ff ff e8 12 c6 e2 fd 48 c7 c7 40 db 71 88 c6 05 b6 a9 f1 06 01 e8 77 91 b4 fd <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
RSP: 0018:ffffc900020b7698 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815c4e91 RDI: fffff52000416ec5
RBP: 0000000000000003 R08: ffff88808bcee040 R09: fffffbfff1852717
R10: fffffbfff1852716 R11: ffffffff8c2938b7 R12: 0000000000008100
R13: ffff8880a8683a04 R14: ffff888097726540 R15: ffff888097726580
 refcount_sub_and_test include/linux/refcount.h:261 [inline]
 sock_wfree+0x1e3/0x240 net/core/sock.c:1973
 sctp_wfree+0x372/0x960 net/sctp/socket.c:9111
 skb_release_head_state+0xe2/0x250 net/core/skbuff.c:651
 skb_release_all+0x11/0x60 net/core/skbuff.c:662
 __kfree_skb net/core/skbuff.c:678 [inline]
 consume_skb net/core/skbuff.c:837 [inline]
 consume_skb+0xf3/0x400 net/core/skbuff.c:831
 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1454 [inline]
 sctp_chunk_put+0x1c0/0x2d0 net/sctp/sm_make_chunk.c:1481
 __sctp_outq_teardown+0x715/0xc60 net/sctp/outqueue.c:257
 sctp_association_free+0x212/0x7e0 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+0x3921/0x4ee0 net/sctp/sm_sideeffect.c:1156
 sctp_primitive_ABORT+0x9b/0xc0 net/sctp/primitive.c:104
 sctp_close+0x22e/0x8a0 net/sctp/socket.c:1512
 inet_release+0xe4/0x1f0 net/ipv4/af_inet.c:427
 __sock_release+0xcd/0x280 net/socket.c:605
 sock_close+0x18/0x20 net/socket.c:1283
 __fput+0x2da/0x850 fs/file_table.c:280
 task_work_run+0x13f/0x1b0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xb53/0x2e10 kernel/exit.c:802
 do_group_exit+0x125/0x340 kernel/exit.c:900
 __do_sys_exit_group kernel/exit.c:911 [inline]
 __se_sys_exit_group kernel/exit.c:909 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:909
 do_syscall_64+0xf6/0x790 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43ef98
Code: Bad RIP value.
RSP: 002b:00007ffc746d2428 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ef98
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004be7a8 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 000000002059aff8 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d01a0 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..