bisecting fixing commit since f8f65382c98a28e3c2b20df9dd4231dca5a11682 building syzkaller on 6b5120a46407f0462e664e15fed3eae5da951c75 testing commit f8f65382c98a28e3c2b20df9dd4231dca5a11682 with gcc (GCC) 8.1.0 run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #4: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #5: crashed: INFO: rcu detected stall in corrupted run #6: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #7: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing current HEAD d6d5df1db6e9d7f8f76d2911707f7d5877251b02 testing commit d6d5df1db6e9d7f8f76d2911707f7d5877251b02 with gcc (GCC) 8.1.0 run #0: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #3: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #4: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #5: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #6: crashed: INFO: rcu detected stall in corrupted run #7: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #8: crashed: INFO: rcu detected stall in corrupted run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl revisions tested: 2, total time: 23m19.180830822s (build: 11m23.690595676s, test: 10m38.818065363s) the crash still happens on HEAD crash: INFO: rcu detected stall in kvm_vcpu_ioctl 8021q: adding VLAN 0 to HW filter on device team0 L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details. hrtimer: interrupt took 46569 ns rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: (detected by 0, t=10502 jiffies, g=5505, q=435) rcu: All QSes seen, last rcu_preempt kthread activity 10502 (4294955621-4294945119), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor2 R running task 26488 7118 5622 0x00000000 Call Trace: sched_show_task.cold.98+0x2e1/0x342 kernel/sched/core.c:5935 print_other_cpu_stall kernel/rcu/tree_stall.h:410 [inline] check_cpu_stall kernel/rcu/tree_stall.h:538 [inline] rcu_pending kernel/rcu/tree.c:2795 [inline] rcu_sched_clock_irq.cold.84+0xb23/0xc3e kernel/rcu/tree.c:2244 update_process_times+0x23/0x50 kernel/time/timer.c:1726 tick_sched_handle+0x77/0x140 kernel/time/tick-sched.c:167 tick_sched_timer+0x43/0x100 kernel/time/tick-sched.c:1299 __run_hrtimer kernel/time/hrtimer.c:1514 [inline] __hrtimer_run_queues+0x332/0xb50 kernel/time/hrtimer.c:1576 hrtimer_interrupt+0x2df/0x760 kernel/time/hrtimer.c:1638 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline] smp_apic_timer_interrupt+0x16f/0x600 arch/x86/kernel/apic/apic.c:1135 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 RIP: 0010:vcpu_enter_guest+0x9f1/0x5540 arch/x86/kvm/x86.c:8194 Code: 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 ba 44 00 00 48 83 3d 3c 47 27 07 00 0f 84 e0 35 00 00 fb 66 0f 1f 44 00 00 <49> 8d be 68 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 RSP: 0018:ffff8881c92ff980 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13 RAX: dffffc0000000000 RBX: ffffffff883321b0 RCX: 0000000000000006 RDX: 1ffffffff1066436 RSI: 0000000000000008 RDI: ffff8881c92e68d4 RBP: ffff8881c92ffa80 R08: 0000000000000006 R09: fffffbfff136e4ee R10: fffffbfff136e4ed R11: ffffffff89b7276f R12: ffff8881bbe300a8 R13: ffffffff883321a8 R14: ffff8881bbe30080 R15: ffff8881bbe300b0 vcpu_run arch/x86/kvm/x86.c:8291 [inline] kvm_arch_vcpu_ioctl_run+0x2e4/0x1350 arch/x86/kvm/x86.c:8498 kvm_vcpu_ioctl+0x507/0xaf0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2768 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x199/0x1160 fs/ioctl.c:696 ksys_ioctl+0x62/0x90 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718 do_syscall_64+0xd0/0x5e0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4571e9 Code: fd b4 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 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f3835d3dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f3835d3e6d4 RCX: 00000000004571e9 RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006 RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004cf7d0 R14: 00000000004c5a59 R15: 0000000000000000 rcu: rcu_preempt kthread starved for 10502 jiffies! g5505 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1 rcu: RCU grace-period kthread stack dump: rcu_preempt R running task 29736 10 2 0x80004000 Call Trace: context_switch kernel/sched/core.c:3384 [inline] __schedule+0x8ca/0x19f0 kernel/sched/core.c:4069 schedule+0xc0/0x260 kernel/sched/core.c:4136 schedule_timeout+0x38b/0xad0 kernel/time/timer.c:1895 rcu_gp_fqs_loop kernel/rcu/tree.c:1639 [inline] rcu_gp_kthread+0x997/0x1820 kernel/rcu/tree.c:1799 kthread+0x334/0x3f0 kernel/kthread.c:255 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352