bisecting fixing commit since 78d697fc93f98054e36a3ab76dca1a88802ba7be building syzkaller on 4a4e0509de520c7139ca2b5606712cbadc550db2 testing commit 78d697fc93f98054e36a3ab76dca1a88802ba7be with gcc (GCC) 8.1.0 kernel signature: 553cf7700bd0e0e3ac72c68fa8387331f2f1bb3e3dfc97fec6c288f932db58e0 all runs: crashed: WARNING: suspicious RCU usage in nf_reinject testing current HEAD 01364dad1d4577e27a57729d41053f661bb8a5b9 testing commit 01364dad1d4577e27a57729d41053f661bb8a5b9 with gcc (GCC) 8.1.0 kernel signature: 54c4ce0abe28fba93cc83383c2c015181b5916da9f4526f0bc39a9af3c5049f2 all runs: crashed: WARNING: suspicious RCU usage in nf_reinject revisions tested: 2, total time: 23m42.002615308s (build: 16m38.753841981s, test: 6m27.978350253s) the crash still happens on HEAD commit msg: Linux 4.14.174 crash: WARNING: suspicious RCU usage in nf_reinject ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ============================= WARNING: suspicious RCU usage 4.14.174-syzkaller #0 Not tainted ----------------------------- net/netfilter/nf_queue.c:227 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by syz-executor.5/7935: #0: (&tsk->futex_exit_mutex){+.+.}, at: [] futex_cleanup_begin+0x18/0x70 kernel/futex.c:3816 #1: (rcu_callback){....}, at: [] __rcu_reclaim kernel/rcu/rcu.h:185 [inline] #1: (rcu_callback){....}, at: [] rcu_do_batch kernel/rcu/tree.c:2699 [inline] #1: (rcu_callback){....}, at: [] invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline] #1: (rcu_callback){....}, at: [] __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline] #1: (rcu_callback){....}, at: [] rcu_process_callbacks+0x8be/0x11e0 kernel/rcu/tree.c:2946 #2: (&(&inst->lock)->rlock){+.-.}, at: [] spin_lock_bh include/linux/spinlock.h:322 [inline] #2: (&(&inst->lock)->rlock){+.-.}, at: [] nfqnl_flush+0x2f/0x270 net/netfilter/nfnetlink_queue.c:232 stack backtrace: CPU: 0 PID: 7935 Comm: syz-executor.5 Not tainted 4.14.174-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 lockdep_rcu_suspicious+0x14a/0x153 kernel/locking/lockdep.c:4665 nf_reinject+0x4e4/0x680 net/netfilter/nf_queue.c:227 nfqnl_flush+0x18d/0x270 net/netfilter/nfnetlink_queue.c:237 instance_destroy_rcu+0x15/0x30 net/netfilter/nfnetlink_queue.c:171 __rcu_reclaim kernel/rcu/rcu.h:195 [inline] rcu_do_batch kernel/rcu/tree.c:2699 [inline] invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline] __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline] rcu_process_callbacks+0x7e0/0x11e0 kernel/rcu/tree.c:2946 __do_softirq+0x246/0x9b0 kernel/softirq.c:288 invoke_softirq kernel/softirq.c:368 [inline] irq_exit+0x15f/0x1a0 kernel/softirq.c:409 exiting_irq arch/x86/include/asm/apic.h:648 [inline] smp_apic_timer_interrupt+0x149/0x5d0 arch/x86/kernel/apic/apic.c:1102 apic_timer_interrupt+0x96/0xa0 arch/x86/entry/entry_64.S:792 RIP: 0010:__mutex_unlock_slowpath+0x19/0x7e0 kernel/locking/mutex.c:1013 RSP: 0018:ffff888089a57a08 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10 RAX: 0000000000000000 RBX: ffff88809eebe400 RCX: 1ffff11013dd7d8e RDX: ffffffff8151b5ef RSI: 0000000000000001 RDI: ffff88809eebf568 RBP: ffff888089a57a20 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: ffff88809eebe400 R12: ffff88809f9cd900 R13: ffff88809eebe400 R14: ffff88809f69ad50 R15: ffff88809eebf508 mutex_unlock+0xd/0x10 kernel/locking/mutex.c:614 futex_cleanup_end kernel/futex.c:3845 [inline] futex_exit_release+0x4f/0x60 kernel/futex.c:3870 exit_mm_release+0x12/0x30 kernel/fork.c:1171 exit_mm kernel/exit.c:500 [inline] do_exit+0x538/0x2cc0 kernel/exit.c:845 do_group_exit+0xf4/0x2f0 kernel/exit.c:955 get_signal+0x2fe/0x1b30 kernel/signal.c:2423 do_signal+0x7f/0x19a0 arch/x86/kernel/signal.c:814 exit_to_usermode_loop+0x114/0x1b0 arch/x86/entry/common.c:160 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline] syscall_return_slowpath arch/x86/entry/common.c:270 [inline] do_syscall_64+0x416/0x5b0 arch/x86/entry/common.c:297 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45c479 RSP: 002b:00007fcf6b633cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000076bf28 RCX: 000000000045c479 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000076bf28 RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000076bf2c R13: 00007ffcc85847df R14: 00007fcf6b6349c0 R15: 000000000076bf2c net_ratelimit: 457 callbacks suppressed ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table net_ratelimit: 1053 callbacks suppressed ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table ip_tables: iptables: counters copy to user failed while replacing table