------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 8754 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 8754 Comm: syz-executor.3 Not tainted 5.6.0-rc6-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+0x1e9/0x30e lib/dump_stack.c:118
 panic+0x264/0x7a0 kernel/panic.c:221
 __warn+0x209/0x210 kernel/panic.c:582
 report_bug+0x1ac/0x2d0 lib/bug.c:195
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0xca/0x1c0 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+0x15b/0x1a0 lib/refcount.c:28
Code: c7 14 01 d1 88 31 c0 e8 d3 33 b3 fd 0f 0b eb 85 e8 5a 55 e0 fd c6 05 2e 81 b1 05 01 48 c7 c7 40 01 d1 88 31 c0 e8 b5 33 b3 fd <0f> 0b e9 64 ff ff ff e8 39 55 e0 fd c6 05 0e 81 b1 05 01 48 c7 c7
RSP: 0018:ffffc900026c78e0 EFLAGS: 00010246
RAX: da8df1ad4b417000 RBX: 0000000000000003 RCX: ffff8880a33ac040
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff815e17a6 R09: ffffed1015d06618
R10: ffffed1015d06618 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff88809fa2e000 R14: ffff88809d8dd040 R15: 1ffff11011714eb0
 sctp_wfree+0x3b1/0x710 net/sctp/socket.c:9111
 skb_release_head_state+0xfb/0x210 net/core/skbuff.c:651
 skb_release_all net/core/skbuff.c:662 [inline]
 __kfree_skb+0x22/0x1c0 net/core/skbuff.c:678
 sctp_chunk_destroy net/sctp/sm_make_chunk.c:1454 [inline]
 sctp_chunk_put+0x17b/0x200 net/sctp/sm_make_chunk.c:1481
 __sctp_outq_teardown+0x80a/0x9d0 net/sctp/outqueue.c:257
 sctp_association_free+0x21e/0x7c0 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+0x3c01/0x5560 net/sctp/sm_sideeffect.c:1156
 sctp_primitive_ABORT+0x93/0xc0 net/sctp/primitive.c:104
 sctp_close+0x231/0x770 net/sctp/socket.c:1512
 inet_release+0x135/0x180 net/ipv4/af_inet.c:427
 __sock_release net/socket.c:605 [inline]
 sock_close+0xd8/0x260 net/socket.c:1283
 __fput+0x2d8/0x730 fs/file_table.c:280
 task_work_run+0x176/0x1b0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:164 [inline]
 prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:195
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4163e1
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:00007fff26ffb810 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000009 RCX: 00000000004163e1
RDX: 0000000000000000 RSI: 0000000000001edc RDI: 0000000000000008
RBP: 0000000000000001 R08: 00000000718cdedc R09: 00000000718cdee0
R10: 00007fff26ffb8f0 R11: 0000000000000293 R12: 000000000076bf00
R13: 0000000000771318 R14: 000000000002cda7 R15: 000000000076bf0c
Kernel Offset: disabled
Rebooting in 86400 seconds..