WARNING: refcount bug in sctp_transport

WARNING: refcount bug in sctp_transport_put (3)
Status: upstream: reported on 2021/03/02 11:00
Reported-by: syzbot+9cf577014b7a043dbb0d@syzkaller.appspotmail.com
First crash: 55d, last: 31d

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	WARNING: refcount bug in sctp_transport_put (2)				2	548d	565d	0/22	auto-closed as invalid on 2020/02/20 05:23
upstream	WARNING: refcount bug in sctp_transport_put				5	919d	983d	0/22	auto-closed as invalid on 2019/04/14 11:41

Sample crash report:

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 15189 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Modules linked in:
CPU: 1 PID: 15189 Comm: syz-executor.3 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Code: e9 db fe ff ff 48 89 df e8 cc ed ee fd e9 8a fe ff ff e8 62 5a ab fd 48 c7 c7 00 d8 c1 89 c6 05 c9 55 e9 09 01 e8 8d 64 fc 04 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
RSP: 0018:ffffc900004f8d08 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888013eb1c40 RSI: ffffffff815c49d5 RDI: fffff5200009f193
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bd76e R11: 0000000000000000 R12: ffff88806f95e820
R13: 1ffff9200009f1a9 R14: ffffffff882d1230 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88802cb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 000000000ab17efc CR3: 00000000249c4000 CR4: 0000000000150ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 sctp_transport_put+0x138/0x180 net/sctp/transport.c:325
 call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1431
 expire_timers kernel/time/timer.c:1476 [inline]
 __run_timers.part.0+0x67c/0xa50 kernel/time/timer.c:1745
 __run_timers kernel/time/timer.c:1726 [inline]
 run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1758
 __do_softirq+0x29b/0x9f6 kernel/softirq.c:345
 invoke_softirq kernel/softirq.c:221 [inline]
 __irq_exit_rcu kernel/softirq.c:422 [inline]
 irq_exit_rcu+0x134/0x200 kernel/softirq.c:434
 sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1100
 </IRQ>
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:199
Code: 0f 1f 44 00 00 55 48 8b 74 24 08 48 89 fd 48 83 c7 18 e8 3e f5 50 f8 48 89 ef e8 66 ab 51 f8 e8 f1 34 71 f8 fb bf 01 00 00 00 <e8> 66 79 45 f8 65 8b 05 4f 47 f9 76 85 c0 74 02 5d c3 e8 ab 9c f7
RSP: 0018:ffffc90008f67918 EFLAGS: 00000206
RAX: 000000000002cdf3 RBX: 0000000000000402 RCX: 1ffffffff1b8bd19
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000001
RBP: ffff88802cb35180 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff8179dd88 R11: 0000000000000000 R12: ffff88802cb35180
R13: ffff888014558000 R14: 0000000000000000 R15: ffff888013eb1c40
 finish_lock_switch kernel/sched/core.c:4074 [inline]
 finish_task_switch.isra.0+0x15d/0x810 kernel/sched/core.c:4191
 context_switch kernel/sched/core.c:4325 [inline]
 __schedule+0x919/0x21b0 kernel/sched/core.c:5073
 preempt_schedule_common+0x45/0xc0 kernel/sched/core.c:5233
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
 __raw_spin_unlock include/linux/spinlock_api_smp.h:152 [inline]
 _raw_spin_unlock+0x36/0x40 kernel/locking/spinlock.c:183
 spin_unlock include/linux/spinlock.h:394 [inline]
 task_unlock include/linux/sched/task.h:173 [inline]
 mm_update_next_owner+0x620/0x7a0 kernel/exit.c:425
 exit_mm kernel/exit.c:500 [inline]
 do_exit+0xb02/0x2a60 kernel/exit.c:812
 do_group_exit+0x125/0x310 kernel/exit.c:922
 get_signal+0x42c/0x2100 kernel/signal.c:2777
 arch_do_signal_or_restart+0x2a8/0x1eb0 arch/x86/kernel/signal.c:789
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x148/0x250 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:301
 __do_fast_syscall_32+0x62/0x90 arch/x86/entry/common.c:143
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:165
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7fa3549
Code: Unable to access opcode bytes at RIP 0xf7fa351f.
RSP: 002b:00000000f559d5fc EFLAGS: 00000296 ORIG_RAX: 0000000000000150
RAX: 0000000000000003 RBX: 000000002001d000 RCX: 0000000000000000
RDX: 00000000ffffffff RSI: 00000000ffffffff RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-qemu-upstream-386	2021/03/22 06:19	upstream	0d02ec6b	bea32f74	.config	log	report			info	WARNING: refcount bug in sctp_transport_put
ci-qemu-upstream-386	2021/02/26 10:08	upstream	2c87f7a3	4c37c133	.config	log	report			info	WARNING: refcount bug in sctp_transport_put