WARNING: CPU: 0 PID: 7987 at kernel/fork.c:718 __put_task_struct+0x3ef/0x620 kernel/fork.c:718 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 7987 Comm: syz-executor4 Not tainted 4.19.0-rc7-next-20181012+ #93 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 kobject: 'loop1' (0000000018dd2c81): kobject_uevent_env Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x3ab lib/dump_stack.c:113 panic+0x238/0x4e7 kernel/panic.c:184 kobject: 'loop1' (0000000018dd2c81): fill_kobj_path: path = '/devices/virtual/block/loop1' __warn.cold.8+0x163/0x1ba kernel/panic.c:536 report_bug+0x254/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969 RIP: 0010:__put_task_struct+0x3ef/0x620 kernel/fork.c:718 Code: 4c 89 ee e8 c3 a3 7b 00 e9 a1 fe ff ff e8 69 55 37 00 0f 0b e9 7c fd ff ff e8 5d 55 37 00 0f 0b e9 87 fd ff ff e8 51 55 37 00 <0f> 0b e9 d0 fc ff ff e8 45 55 37 00 49 8d 87 90 05 00 00 31 f6 48 RSP: 0018:ffff88017d416fb0 EFLAGS: 00010093 RAX: ffff8801b90ae440 RBX: ffff8801b90ae440 RCX: ffffffff814711cd RDX: 0000000000000000 RSI: ffffffff814714ff RDI: 0000000000000005 RBP: ffff88017d417090 R08: ffff8801b90ae440 R09: ffffed0037215c8c R10: ffffed0037215c8c R11: ffff8801b90ae463 R12: 1ffff1002fa82df9 R13: 0000000000000000 R14: ffff88017d417068 R15: ffff8801d328a340 put_task_struct include/linux/sched/task.h:96 [inline] perf_event_exit_task_context kernel/events/core.c:11108 [inline] perf_event_exit_task+0xca6/0x1070 kernel/events/core.c:11157 do_exit+0x1ae2/0x2610 kernel/exit.c:876 do_group_exit+0x177/0x440 kernel/exit.c:970 get_signal+0x8a8/0x1970 kernel/signal.c:2517 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457569 Code: fd b3 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 b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f446d634cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca RAX: fffffffffffffe00 RBX: 000000000072bf08 RCX: 0000000000457569 RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000072bf08 RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000072bf0c R13: 00007ffe0fb2d8cf R14: 00007f446d6359c0 R15: 0000000000000000 ====================================================== WARNING: possible circular locking dependency detected 4.19.0-rc7-next-20181012+ #93 Not tainted ------------------------------------------------------ syz-executor4/7987 is trying to acquire lock: 000000002c77104b ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70 kernel/locking/semaphore.c:136 but task is already holding lock: 00000000ce208ea0 (&ctx->lock){-...}, at: perf_event_exit_task_context kernel/events/core.c:11098 [inline] 00000000ce208ea0 (&ctx->lock){-...}, at: perf_event_exit_task+0x420/0x1070 kernel/events/core.c:11157 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&ctx->lock){-...}: __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144 perf_event_context_sched_out kernel/events/core.c:3124 [inline] __perf_event_task_sched_out+0xd5c/0x1bf0 kernel/events/core.c:3216 perf_event_task_sched_out include/linux/perf_event.h:1112 [inline] prepare_task_switch kernel/sched/core.c:2615 [inline] context_switch kernel/sched/core.c:2796 [inline] __schedule+0x103b/0x21d0 kernel/sched/core.c:3480 schedule+0xfe/0x460 kernel/sched/core.c:3524 freezable_schedule include/linux/freezer.h:172 [inline] futex_wait_queue_me+0x3f9/0x840 kernel/futex.c:2530 futex_wait+0x45c/0xa50 kernel/futex.c:2645 do_futex+0x31a/0x26d0 kernel/futex.c:3528 __do_sys_futex kernel/futex.c:3589 [inline] __se_sys_futex kernel/futex.c:3557 [inline] __x64_sys_futex+0x472/0x6a0 kernel/futex.c:3557 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&rq->lock){-.-.}: __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144 rq_lock kernel/sched/sched.h:1125 [inline] task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9752 sched_fork+0x443/0xba0 kernel/sched/core.c:2359 copy_process+0x2585/0x8760 kernel/fork.c:1887 _do_fork+0x1cb/0x11c0 kernel/fork.c:2216 kernel_thread+0x34/0x40 kernel/fork.c:2275 rest_init+0x28/0x372 init/main.c:408 arch_call_rest_init+0xe/0x1b start_kernel+0x9f0/0xa2b init/main.c:744 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470 x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #1 (&p->pi_lock){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 try_to_wake_up+0xd2/0x12e0 kernel/sched/core.c:1965 wake_up_process+0x10/0x20 kernel/sched/core.c:2129 __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262 up+0x13c/0x1c0 kernel/locking/semaphore.c:187 __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:243 console_unlock+0x80c/0x1160 kernel/printk/printk.c:2426 vprintk_emit+0x33d/0x930 kernel/printk/printk.c:1921 vprintk_default+0x28/0x30 kernel/printk/printk.c:1962 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 printk+0xa7/0xcf kernel/printk/printk.c:1995 check_stack_usage kernel/exit.c:755 [inline] do_exit.cold.18+0x5b/0x21f kernel/exit.c:916 do_group_exit+0x177/0x440 kernel/exit.c:970 __do_sys_exit_group kernel/exit.c:981 [inline] __se_sys_exit_group kernel/exit.c:979 [inline] __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:979 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 ((console_sem).lock){-.-.}: lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3840 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136 __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:226 console_trylock+0x15/0xa0 kernel/printk/printk.c:2244 console_trylock_spinning kernel/printk/printk.c:1648 [inline] vprintk_emit+0x322/0x930 kernel/printk/printk.c:1920 vprintk_default+0x28/0x30 kernel/printk/printk.c:1962 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 printk+0xa7/0xcf kernel/printk/printk.c:1995 __warn.cold.8+0x73/0x1ba kernel/panic.c:518 report_bug+0x254/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969 __put_task_struct+0x3ef/0x620 kernel/fork.c:718 put_task_struct include/linux/sched/task.h:96 [inline] perf_event_exit_task_context kernel/events/core.c:11108 [inline] perf_event_exit_task+0xca6/0x1070 kernel/events/core.c:11157 do_exit+0x1ae2/0x2610 kernel/exit.c:876 do_group_exit+0x177/0x440 kernel/exit.c:970 get_signal+0x8a8/0x1970 kernel/signal.c:2517 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: (console_sem).lock --> &rq->lock --> &ctx->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ctx->lock); lock(&rq->lock); lock(&ctx->lock); lock((console_sem).lock); *** DEADLOCK *** 2 locks held by syz-executor4/7987: #0: 00000000134f14f1 (&ctx->mutex){+.+.}, at: perf_event_exit_task_context kernel/events/core.c:11091 [inline] #0: 00000000134f14f1 (&ctx->mutex){+.+.}, at: perf_event_exit_task+0x40d/0x1070 kernel/events/core.c:11157 #1: 00000000ce208ea0 (&ctx->lock){-...}, at: perf_event_exit_task_context kernel/events/core.c:11098 [inline] #1: 00000000ce208ea0 (&ctx->lock){-...}, at: perf_event_exit_task+0x420/0x1070 kernel/events/core.c:11157 stack backtrace: CPU: 0 PID: 7987 Comm: syz-executor4 Not tainted 4.19.0-rc7-next-20181012+ #93 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x3ab lib/dump_stack.c:113 print_circular_bug.isra.35.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1861 [inline] check_prevs_add kernel/locking/lockdep.c:1974 [inline] validate_chain kernel/locking/lockdep.c:2345 [inline] __lock_acquire+0x3445/0x4da0 kernel/locking/lockdep.c:3337 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3840 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136 __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:226 console_trylock+0x15/0xa0 kernel/printk/printk.c:2244 console_trylock_spinning kernel/printk/printk.c:1648 [inline] vprintk_emit+0x322/0x930 kernel/printk/printk.c:1920 vprintk_default+0x28/0x30 kernel/printk/printk.c:1962 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398 printk+0xa7/0xcf kernel/printk/printk.c:1995 __warn.cold.8+0x73/0x1ba kernel/panic.c:518 report_bug+0x254/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969 RIP: 0010:__put_task_struct+0x3ef/0x620 kernel/fork.c:718 Code: 4c 89 ee e8 c3 a3 7b 00 e9 a1 fe ff ff e8 69 55 37 00 0f 0b e9 7c fd ff ff e8 5d 55 37 00 0f 0b e9 87 fd ff ff e8 51 55 37 00 <0f> 0b e9 d0 fc ff ff e8 45 55 37 00 49 8d 87 90 05 00 00 31 f6 48 RSP: 0018:ffff88017d416fb0 EFLAGS: 00010093 RAX: ffff8801b90ae440 RBX: ffff8801b90ae440 RCX: ffffffff814711cd RDX: 0000000000000000 RSI: ffffffff814714ff RDI: 0000000000000005 RBP: ffff88017d417090 R08: ffff8801b90ae440 R09: ffffed0037215c8c R10: ffffed0037215c8c R11: ffff8801b90ae463 R12: 1ffff1002fa82df9 R13: 0000000000000000 R14: ffff88017d417068 R15: ffff8801d328a340 put_task_struct include/linux/sched/task.h:96 [inline] perf_event_exit_task_context kernel/events/core.c:11108 [inline] perf_event_exit_task+0xca6/0x1070 kernel/events/core.c:11157 do_exit+0x1ae2/0x2610 kernel/exit.c:876 do_group_exit+0x177/0x440 kernel/exit.c:970 get_signal+0x8a8/0x1970 kernel/signal.c:2517 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816 ? __sanitizer_cov_trac Lost 25 message(s)! Kernel Offset: disabled Rebooting in 86400 seconds..