===============================
[ INFO: suspicious RCU usage. ]
4.9.111-g03c70fe #10 Not tainted
-------------------------------
kernel/rcu/tree_plugin.h:678 Illegal synchronize_rcu() in RCU read-side critical section!
capability: warning: `syz-executor3' uses 32-bit capabilities (legacy support in use)

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
3 locks held by syz-executor5/7769:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff815ecfad>] seq_read+0xdd/0x12e0 fs/seq_file.c:178
 #1:  (rcu_read_lock){......}, at: [<ffffffff835e1230>] igmp6_mcf_seq_start+0x0/0x550 net/ipv6/mcast.c:2840
 #2:  (rcu_callback){......}, at: [<ffffffff8128784e>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128784e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128784e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128784e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128784e>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037

stack backtrace:
CPU: 0 PID: 7769 Comm: syz-executor5 Not tainted 4.9.111-g03c70fe #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db207d98 ffffffff81eb2729 ffff8801a51ee000 0000000000000000
 0000000000000002 ffffffff83c6df20 ffff8801c156cdd8 ffff8801db207dc8
 ffffffff81426090 ffff8801c156cc80 ffff8801a9348848 ffff8801a9348048
Call Trace:
 <IRQ> [   77.494624]  [<ffffffff81eb2729>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [   77.494624]  [<ffffffff81eb2729>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81426090>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff812840e8>] synchronize_rcu+0x68/0x90 kernel/rcu/tree_plugin.h:675
 [<ffffffff836bbeda>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bc267>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836bcb22>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff83020095>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff8128776e>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff8128776e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff8128776e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff8128776e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff8128776e>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff839ff8bb>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff839f9cdc>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:843
 <EOI> [   77.596471]  [<ffffffff81149819>] do_softirq.part.14+0x99/0xb0 kernel/softirq.c:328
 [<ffffffff811498f6>] do_softirq arch/x86/include/asm/preempt.h:22 [inline]
 [<ffffffff811498f6>] __local_bh_enable_ip+0xc6/0xd0 kernel/softirq.c:181
 [<ffffffff839f8740>] __raw_read_unlock_bh include/linux/rwlock_api_smp.h:251 [inline]
 [<ffffffff839f8740>] _raw_read_unlock_bh+0x30/0x40 kernel/locking/spinlock.c:279
 [<ffffffff835e165b>] igmp6_mcf_get_first net/ipv6/mcast.c:2770 [inline]
 [<ffffffff835e165b>] igmp6_mcf_get_idx net/ipv6/mcast.c:2809 [inline]
 [<ffffffff835e165b>] igmp6_mcf_seq_start+0x42b/0x550 net/ipv6/mcast.c:2820
 [<ffffffff815ed175>] seq_read+0x2a5/0x12e0 fs/seq_file.c:235
 [<ffffffff816d57e9>] proc_reg_read+0xf9/0x180 fs/proc/inode.c:202
 [<ffffffff8156f3e5>] do_loop_readv_writev.part.18+0xd5/0x280 fs/read_write.c:718
 [<ffffffff81574597>] do_loop_readv_writev fs/read_write.c:707 [inline]
 [<ffffffff81574597>] compat_do_readv_writev+0x567/0x7a0 fs/read_write.c:1091
IPVS: set_ctl: invalid protocol: 0 255.255.255.255:0
 [<ffffffff815748b2>] compat_readv+0xe2/0x150 fs/read_write.c:1120
 [<ffffffff81574c42>] do_compat_preadv64+0x152/0x180 fs/read_write.c:1169
 [<ffffffff815771db>] C_SYSC_preadv fs/read_write.c:1189 [inline]
 [<ffffffff815771db>] compat_SyS_preadv+0x3b/0x50 fs/read_write.c:1183
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff839fa3d0>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137
ODEBUG: object ffff8801db207d20 is NOT on stack ffff8801a8a08000, but annotated
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7769 at lib/debugobjects.c:303 debug_object_is_on_stack lib/debugobjects.c:303 [inline]
WARNING: CPU: 0 PID: 7769 at lib/debugobjects.c:303 __debug_object_init.cold.10+0x6b/0x2b0 lib/debugobjects.c:329