bisecting cause commit starting from f8f65382c98a28e3c2b20df9dd4231dca5a11682 building syzkaller on 6b5120a46407f0462e664e15fed3eae5da951c75 testing commit f8f65382c98a28e3c2b20df9dd4231dca5a11682 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 kvm_vcpu_ioctl 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 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 release v4.18 testing commit 94710cac0ef4ee177a63b5227664b38c95bbf703 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 kvm_vcpu_ioctl 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 corrupted 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 kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.17 testing commit 29dcea88779c856c7dc92040a0c01233263101d4 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 kvm_vcpu_ioctl 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 release v4.16 testing commit 0adb32858b0bddf4ada5f364a84ed60b196dbcda 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 kvm_vcpu_ioctl run #3: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #4: crashed: INFO: rcu detected stall in corrupted run #5: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #6: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #7: crashed: INFO: rcu detected stall in corrupted run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.15 testing commit d8a5b80568a9cb66810e75b182018e9edb68e8ff 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 corrupted run #4: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #5: crashed: unregister_netdevice: waiting for DEV to become free run #6: crashed: unregister_netdevice: waiting for DEV to become free run #7: OK run #8: OK run #9: OK testing release v4.14 testing commit bebc6082da0a9f5d47a1ea2edc099bf671058bd4 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 kvm_vcpu_ioctl 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 corrupted run #5: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #6: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #7: crashed: INFO: rcu detected stall in corrupted run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.13 testing commit 569dbb88e80deb68974ef6fdd6a13edb9d686261 with gcc (GCC) 8.1.0 all runs: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.12 testing commit 6f7da290413ba713f0cdd9ff1a2a9bb129ef4f6c 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 kvm_vcpu_ioctl run #2: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #3: crashed: INFO: rcu detected stall in corrupted 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 release v4.11 testing commit a351e9b9fc24e982ec2f0e76379a49826036da12 with gcc (GCC) 7.3.0 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 corrupted 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 corrupted run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.10 testing commit c470abd4fde40ea6a0846a2beab642a578c0b8cd with gcc (GCC) 5.5.0 run #0: crashed: INFO: rcu detected stall in corrupted 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 corrupted run #5: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #6: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #7: crashed: INFO: rcu detected stall in corrupted run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in corrupted testing release v4.9 testing commit 69973b830859bc6529a7a0468ba0d80ee5117826 with gcc (GCC) 5.5.0 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 corrupted run #3: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #4: crashed: INFO: rcu detected stall in corrupted 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 corrupted run #8: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.8 testing commit c8d2bc9bc39ebea8437fd974fdbc21847bb897a3 with gcc (GCC) 5.5.0 run #0: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl 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 release v4.7 testing commit 523d939ef98fd712632d93a5a2b588e477a7565e with gcc (GCC) 5.5.0 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 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 testing release v4.6 testing commit 2dcd0af568b0cf583645c8a317dd12e344b1c72a with gcc (GCC) 5.5.0 run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in corrupted 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 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 testing release v4.5 testing commit b562e44f507e863c6792946e4e1b1449fbbac85d with gcc (GCC) 5.5.0 run #0: crashed: BUG: unable to handle kernel NULL pointer dereference in kvm_apic_set_version run #1: crashed: INFO: rcu detected stall in corrupted 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 corrupted run #5: crashed: INFO: rcu detected stall in corrupted 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 kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl testing release v4.4 testing commit afd2ff9b7e1b367172f18ba7f693dfb62bdcb2dc with gcc (GCC) 5.5.0 run #0: crashed: INFO: rcu detected stall in corrupted run #1: crashed: INFO: rcu detected stall in corrupted run #2: crashed: INFO: rcu detected stall in corrupted run #3: crashed: INFO: rcu detected stall in corrupted run #4: crashed: INFO: rcu detected stall in corrupted 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 corrupted run #8: crashed: INFO: rcu detected stall in corrupted run #9: crashed: INFO: rcu detected stall in corrupted testing release v4.3 testing commit 6a13feb9c82803e2b815eca72fa7a9f5561d7861 with gcc (GCC) 5.5.0 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 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 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 testing release v4.2 testing commit 64291f7db5bd8150a74ad2036f1037e6a0428df2 with gcc (GCC) 5.5.0 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 kvm_vcpu_ioctl run #9: crashed: INFO: rcu detected stall in corrupted testing release v4.1 testing commit b953c0d234bc72e8489d3bf51a276c5c4ec85345 with gcc (GCC) 5.5.0 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 corrupted run #3: crashed: INFO: rcu detected stall in kvm_vcpu_ioctl run #4: crashed: INFO: rcu detected stall in corrupted 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 corrupted run #8: crashed: INFO: rcu detected stall in corrupted run #9: crashed: INFO: rcu detected stall in corrupted revisions tested: 19, total time: 3h19m41.128235833s (build: 1h20m5.850751286s, test: 1h53m36.757104712s) the crash already happened on the oldest tested release crash: INFO: rcu detected stall in corrupted bridge0: port 1(bridge_slave_0) entered forwarding state bridge0: port 2(bridge_slave_1) entered forwarding state bridge0: port 1(bridge_slave_0) entered forwarding state bridge0: port 2(bridge_slave_1) entered forwarding state bridge0: port 1(bridge_slave_0) entered forwarding state INFO: rcu_preempt detected stalls on CPUs/tasks: INFO: rcu_sched detected stalls on CPUs/tasks: (detected by 1, t=10502 jiffies, g=-285, c=-286, q=1) All QSes seen, last rcu_sched kthread activity 10502 (4294954879-4294944377), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor1 R running task 13408 6312 4554 0x00000000 ffff880212ed0b90 ffff88021fd03d98 ffffffff811a8e12 0000000000002906 ffffffff8325e340 fffffffffffffee3 0000000000000000 ffff88021fd03e28 ffffffff811efa69 0000000000000000 0000000000000000 ffff88021fd00000 Call Trace: <IRQ> [<ffffffff811a8e12>] sched_show_task+0xf2/0x1a0 kernel/sched/core.c:4545 [<ffffffff811efa69>] print_other_cpu_stall kernel/rcu/tree.c:1226 [inline] [<ffffffff811efa69>] check_cpu_stall kernel/rcu/tree.c:1332 [inline] [<ffffffff811efa69>] __rcu_pending kernel/rcu/tree.c:3422 [inline] [<ffffffff811efa69>] rcu_pending kernel/rcu/tree.c:3486 [inline] [<ffffffff811efa69>] rcu_check_callbacks+0xd69/0xd70 kernel/rcu/tree.c:2703 [<ffffffff811f5f04>] update_process_times+0x34/0x60 kernel/time/timer.c:1396 [<ffffffff812087e0>] tick_sched_handle.isra.22+0x20/0x60 kernel/time/tick-sched.c:151 [<ffffffff81208a9c>] tick_sched_timer+0x3c/0x80 kernel/time/tick-sched.c:1124 [<ffffffff811f6b06>] __run_hrtimer+0xe6/0x760 kernel/time/hrtimer.c:1220 [<ffffffff811f7dd3>] hrtimer_interrupt+0x103/0x230 kernel/time/hrtimer.c:1299 [<ffffffff810beba5>] local_apic_timer_interrupt+0x35/0x60 arch/x86/kernel/apic/apic.c:890 [<ffffffff810bedfc>] smp_apic_timer_interrupt+0x3c/0x50 arch/x86/kernel/apic/apic.c:914 [<ffffffff826686b3>] apic_timer_interrupt+0x73/0x80 arch/x86/kernel/entry_64.S:923 <EOI> [<ffffffff8104cff9>] ? __vmx_complete_interrupts.part.76+0xb9/0xc0 arch/x86/kvm/vmx.c:8094 [<ffffffff8102216f>] vcpu_enter_guest arch/x86/kvm/x86.c:6398 [inline] [<ffffffff8102216f>] vcpu_run arch/x86/kvm/x86.c:6479 [inline] [<ffffffff8102216f>] kvm_arch_vcpu_ioctl_run+0xfef/0x1aa0 arch/x86/kvm/x86.c:6634 [<ffffffff81008c34>] kvm_vcpu_ioctl+0x314/0x7b0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2130 [<ffffffff8131bd18>] vfs_ioctl fs/ioctl.c:43 [inline] [<ffffffff8131bd18>] do_vfs_ioctl+0x2d8/0x510 fs/ioctl.c:607 [<ffffffff8131bfd1>] SYSC_ioctl fs/ioctl.c:622 [inline] [<ffffffff8131bfd1>] SyS_ioctl+0x81/0xa0 fs/ioctl.c:613 [<ffffffff82667772>] system_call_fastpath+0x16/0x7a rcu_sched kthread starved for 10502 jiffies! (detected by 0, t=10526 jiffies, g=391, c=390, q=473) All QSes seen, last rcu_preempt kthread activity 10527 (4294954904-4294944377), jiffies_till_next_fqs=1, root ->qsmask 0x0 syz-executor2 R running task 13328 6382 4555 0x00000000 ffff88020ff02150 ffff88021fc03d98 ffffffff811a8e12 000000000000291f ffffffff8325d280 0000000000000187 0000000000000000 ffff88021fc03e28 ffffffff811efa69 0000000000000000 0000000000000000 ffff88021fc00000 Call Trace: <IRQ> [<ffffffff811a8e12>] sched_show_task+0xf2/0x1a0 kernel/sched/core.c:4545 [<ffffffff811efa69>] print_other_cpu_stall kernel/rcu/tree.c:1226 [inline] [<ffffffff811efa69>] check_cpu_stall kernel/rcu/tree.c:1332 [inline] [<ffffffff811efa69>] __rcu_pending kernel/rcu/tree.c:3422 [inline] [<ffffffff811efa69>] rcu_pending kernel/rcu/tree.c:3486 [inline] [<ffffffff811efa69>] rcu_check_callbacks+0xd69/0xd70 kernel/rcu/tree.c:2703 [<ffffffff811f5f04>] update_process_times+0x34/0x60 kernel/time/timer.c:1396 [<ffffffff812087e0>] tick_sched_handle.isra.22+0x20/0x60 kernel/time/tick-sched.c:151 [<ffffffff81208a9c>] tick_sched_timer+0x3c/0x80 kernel/time/tick-sched.c:1124 [<ffffffff811f6b06>] __run_hrtimer+0xe6/0x760 kernel/time/hrtimer.c:1220 [<ffffffff811f7dd3>] hrtimer_interrupt+0x103/0x230 kernel/time/hrtimer.c:1299 [<ffffffff810beba5>] local_apic_timer_interrupt+0x35/0x60 arch/x86/kernel/apic/apic.c:890 [<ffffffff810bedfc>] smp_apic_timer_interrupt+0x3c/0x50 arch/x86/kernel/apic/apic.c:914 [<ffffffff826686b3>] apic_timer_interrupt+0x73/0x80 arch/x86/kernel/entry_64.S:923 <EOI> [<ffffffff8104cff9>] ? __vmx_complete_interrupts.part.76+0xb9/0xc0 arch/x86/kvm/vmx.c:8094 [<ffffffff8102216f>] vcpu_enter_guest arch/x86/kvm/x86.c:6398 [inline] [<ffffffff8102216f>] vcpu_run arch/x86/kvm/x86.c:6479 [inline] [<ffffffff8102216f>] kvm_arch_vcpu_ioctl_run+0xfef/0x1aa0 arch/x86/kvm/x86.c:6634 [<ffffffff81008c34>] kvm_vcpu_ioctl+0x314/0x7b0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2130 [<ffffffff8131bd18>] vfs_ioctl fs/ioctl.c:43 [inline] [<ffffffff8131bd18>] do_vfs_ioctl+0x2d8/0x510 fs/ioctl.c:607 [<ffffffff8131bfd1>] SYSC_ioctl fs/ioctl.c:622 [inline] [<ffffffff8131bfd1>] SyS_ioctl+0x81/0xa0 fs/ioctl.c:613 [<ffffffff82667772>] system_call_fastpath+0x16/0x7a rcu_preempt kthread starved for 10547 jiffies!