WARNING: refcount bug in l2tp_session

Title	Replies (including bot)	Last reply
WARNING: refcount bug in l2tp_session_free	0 (1)	2020/08/07 07:30

------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 6980 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: 6980 Comm: syz-executor.1 Not tainted 5.8.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1f0/0x31e lib/dump_stack.c:118 panic+0x264/0x7a0 kernel/panic.c:231 __warn+0x227/0x250 kernel/panic.c:600 report_bug+0x1b1/0x2e0 lib/bug.c:198 handle_bug+0x42/0x80 arch/x86/kernel/traps.c:235 exc_invalid_op+0x16/0x40 arch/x86/kernel/traps.c:255 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:540 RIP: 0010:refcount_warn_saturate+0x15b/0x1a0 lib/refcount.c:28 Code: c7 2a 86 14 89 31 c0 e8 d3 f2 a8 fd 0f 0b eb 85 e8 2a 32 d7 fd c6 05 43 cc eb 05 01 48 c7 c7 56 86 14 89 31 c0 e8 b5 f2 a8 fd <0f> 0b e9 64 ff ff ff e8 09 32 d7 fd c6 05 23 cc eb 05 01 48 c7 c7 RSP: 0018:ffffc90000da8de8 EFLAGS: 00010246 RAX: d0e66feebea22600 RBX: 0000000000000003 RCX: ffff888086b3c200 RDX: 0000000080000102 RSI: 0000000080000102 RDI: 0000000000000000 RBP: 0000000000000003 R08: ffffffff815dd389 R09: ffffed1015d241c3 R10: ffffed1015d241c3 R11: 0000000000000000 R12: ffff888000f3f040 R13: dffffc0000000000 R14: ffff8880a9256800 R15: ffff888000f3f0c0 l2tp_tunnel_dec_refcount include/linux/refcount.h:274 [inline] l2tp_session_free+0x1a5/0x1f0 net/l2tp/l2tp_core.c:1570 __sk_destruct+0x50/0x770 net/core/sock.c:1786 rcu_do_batch kernel/rcu/tree.c:2414 [inline] rcu_core+0x816/0x1120 kernel/rcu/tree.c:2641 __do_softirq+0x268/0x80c kernel/softirq.c:292 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711 </IRQ> __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline] do_softirq_own_stack+0xe0/0x1a0 arch/x86/kernel/irq_64.c:77 invoke_softirq kernel/softirq.c:387 [inline] __irq_exit_rcu+0x1e1/0x1f0 kernel/softirq.c:417 irq_exit_rcu+0x6/0x50 kernel/softirq.c:429 sysvec_apic_timer_interrupt+0x117/0x130 arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585 RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline] RIP: 0010:_raw_spin_unlock_irq+0x57/0x80 kernel/locking/spinlock.c:199 Code: 00 00 00 00 fc ff df 80 3c 08 00 74 0c 48 c7 c7 08 c8 4b 89 e8 da 40 93 f9 48 83 3d aa 67 2b 01 00 74 25 fb 66 0f 1f 44 00 00 <bf> 01 00 00 00 e8 af 38 30 f9 65 8b 05 94 9d e1 77 85 c0 74 02 5b RSP: 0018:ffffc90004957cb8 EFLAGS: 00000282 RAX: 1ffffffff1297901 RBX: ffff8880ae9358c0 RCX: dffffc0000000000 RDX: 0000000040000000 RSI: 0000000000000000 RDI: ffffffff8820602f RBP: ffffc90004957d18 R08: ffffffff817a3350 R09: ffffed1015d26b19 R10: ffffed1015d26b19 R11: 0000000000000000 R12: ffff8880ae9358c0 R13: ffff888086b3c200 R14: ffff8880ae936308 R15: dffffc0000000000 finish_task_switch+0x24f/0x550 kernel/sched/core.c:3297 context_switch kernel/sched/core.c:3461 [inline] __schedule+0x859/0xcf0 kernel/sched/core.c:4219 schedule+0x188/0x220 kernel/sched/core.c:4294 freezable_schedule include/linux/freezer.h:172 [inline] do_nanosleep+0x1ae/0x680 kernel/time/hrtimer.c:1879 hrtimer_nanosleep kernel/time/hrtimer.c:1932 [inline] __do_sys_nanosleep kernel/time/hrtimer.c:1966 [inline] __se_sys_nanosleep+0x3d5/0x5c0 kernel/time/hrtimer.c:1953 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45a870 Code: c0 5b 5d c3 66 0f 1f 44 00 00 8b 04 24 48 83 c4 18 5b 5d c3 66 0f 1f 44 00 00 83 3d e1 f5 84 00 00 75 14 b8 23 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 54 d1 fb ff c3 48 83 ec 08 e8 8a 46 00 00 RSP: 002b:00007ffd534d3838 EFLAGS: 00000246 ORIG_RAX: 0000000000000023 RAX: ffffffffffffffda RBX: 0000000000145c62 RCX: 000000000045a870 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007ffd534d3840 RBP: 0000000000001962 R08: 0000000000000001 R09: 0000000001ead940 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000008 R13: 00007ffd534d3890 R14: 0000000000145c30 R15: 00007ffd534d38a0 Kernel Offset: disabled Rebooting in 86400 seconds..