refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 8846 at lib/refcount.c:28 refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 8846 Comm: syz-executor.4 Not tainted 5.6.0-rc5-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 d4 00 d1 88 31 c0 e8 33 1f b3 fd 0f 0b eb 85 e8 2a 4a e0 fd c6 05 4e 70 b1 05 01 48 c7 c7 00 01 d1 88 31 c0 e8 15 1f b3 fd <0f> 0b e9 64 ff ff ff e8 09 4a e0 fd c6 05 2e 70 b1 05 01 48 c7 c7
RSP: 0018:ffffc900039a7598 EFLAGS: 00010246
RAX: 353b8d265c78c300 RBX: 0000000000000003 RCX: ffff88809654c300
RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff815e16d6 R09: fffffbfff15dbb2e
R10: fffffbfff15dbb2e R11: 0000000000000000 R12: ffff8880a771c400
R13: ffff8880a35a0000 R14: 1ffff11014ee3880 R15: dffffc0000000000
 sctp_wfree+0x436/0x7e0 net/sctp/socket.c:9127
 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+0x2aa/0x7d0 net/sctp/socket.c:1526
 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
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x5ef/0x1f80 kernel/exit.c:801
 do_group_exit+0x15e/0x2c0 kernel/exit.c:899
 get_signal+0x13cf/0x1d60 kernel/signal.c:2739
 do_signal+0x33/0x610 arch/x86/kernel/signal.c:813
 exit_to_usermode_loop arch/x86/entry/common.c:160 [inline]
 prepare_exit_to_usermode+0x32a/0x600 arch/x86/entry/common.c:195
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45c4a9
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb1cfc2ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: 0000000000000003 RBX: 00007fb1cfc2b6d4 RCX: 000000000045c4a9
RDX: 000000000000007a RSI: 0000000000000084 RDI: 0000000000000004
RBP: 000000000076c060 R08: 000000002034f000 R09: 0000000000000000
R10: 000000002059aff8 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000001a4 R14: 00000000004d1fc0 R15: 000000000076c06c
Kernel Offset: disabled
Rebooting in 86400 seconds..