Hello, syzbot found the following issue on: HEAD commit: 4fa640dc Merge tag 'vfio-v5.8-rc7' of git://github.com/awi.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12c738a0900000 kernel config: https://syzkaller.appspot.com/x/.config?x=f87a5e4232fdb267 dashboard link: https://syzkaller.appspot.com/bug?extid=0c6da80218456f1edc36 compiler: gcc (GCC) 10.1.0-syz 20200507 userspace arch: i386 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14e2a437100000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13af00e8900000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+0c6da80218456f1edc36@xxxxxxxxxxxxxxxxxxxxxxxxx INFO: task kworker/0:5:2530 blocked for more than 144 seconds. Not tainted 5.8.0-rc6-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/0:5 D26496 2530 2 0x00004000 Workqueue: events free_ipc Call Trace: context_switch kernel/sched/core.c:3458 [inline] __schedule+0x91f/0x2250 kernel/sched/core.c:4215 schedule+0xd0/0x2a0 kernel/sched/core.c:4290 schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1884 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion+0x163/0x260 kernel/sched/completion.c:138 __wait_rcu_gp+0x217/0x2d0 kernel/rcu/update.c:411 synchronize_rcu+0x10a/0x180 kernel/rcu/tree.c:3430 kern_unmount fs/namespace.c:3861 [inline] kern_unmount+0x67/0xe0 fs/namespace.c:3856 free_ipc_ns ipc/namespace.c:123 [inline] free_ipc+0xbe/0x1b0 ipc/namespace.c:141 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 kthread+0x3b5/0x4a0 kernel/kthread.c:291 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 INFO: task syz-executor643:6834 blocked for more than 144 seconds. Not tainted 5.8.0-rc6-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor643 D24000 6834 6833 0xa0024002 Call Trace: context_switch kernel/sched/core.c:3458 [inline] __schedule+0x91f/0x2250 kernel/sched/core.c:4215 schedule+0xd0/0x2a0 kernel/sched/core.c:4290 schedule_timeout+0x1d8/0x250 kernel/time/timer.c:1884 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion+0x163/0x260 kernel/sched/completion.c:138 rcu_barrier+0x2d1/0x4a0 kernel/rcu/tree.c:3661 netdev_run_todo+0x100/0xac0 net/core/dev.c:9758 tun_detach drivers/net/tun.c:711 [inline] tun_chr_close+0xf5/0x180 drivers/net/tun.c:3423 __fput+0x33c/0x880 fs/file_table.c:281 task_work_run+0xdd/0x190 kernel/task_work.c:135 exit_task_work include/linux/task_work.h:25 [inline] do_exit+0xb72/0x2a40 kernel/exit.c:805 do_group_exit+0x125/0x310 kernel/exit.c:903 __do_sys_exit_group kernel/exit.c:914 [inline] __se_sys_exit_group kernel/exit.c:912 [inline] __ia32_sys_exit_group+0x3a/0x50 kernel/exit.c:912 do_syscall_32_irqs_on+0x3f/0x60 arch/x86/entry/common.c:428 __do_fast_syscall_32 arch/x86/entry/common.c:475 [inline] do_fast_syscall_32+0x7f/0x120 arch/x86/entry/common.c:503 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c RIP: 0023:0xf7fef569 Code: Bad RIP value. RSP: 002b:00000000ffdacd8c EFLAGS: 00000292 ORIG_RAX: 00000000000000fc RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00000000080f7b38 RDX: 0000000000000000 RSI: 00000000080dffbc RDI: 00000000080f7b40 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Showing all locks held in the system: 1 lock held by khungtaskd/1155: #0: ffffffff89bc11c0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:5779 2 locks held by kworker/0:5/2530: #0: ffff8880aa026d38 ((wq_completion)events){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: ffff8880aa026d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic64_set include/asm-generic/atomic-instrumented.h:856 [inline] #0: ffff8880aa026d38 ((wq_completion)events){+.+.}-{0:0}, at: atomic_long_set include/asm-generic/atomic-long.h:41 [inline] #0: ffff8880aa026d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:616 [inline] #0: ffff8880aa026d38 ((wq_completion)events){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8880aa026d38 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x82b/0x1670 kernel/workqueue.c:2240 #1: ffffc9000804fda8 (free_ipc_work){+.+.}-{0:0}, at: process_one_work+0x85f/0x1670 kernel/workqueue.c:2244 1 lock held by in:imklog/6529: #0: ffff88809f8eadf0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe9/0x100 fs/file.c:826 1 lock held by syz-executor643/6834: #0: ffffffff89bc5728 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x44/0x4a0 kernel/rcu/tree.c:3596 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1155 Comm: khungtaskd Not tainted 5.8.0-rc6-syzkaller #0 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+0x18f/0x20d lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline] watchdog+0xd7d/0x1000 kernel/hung_task.c:295 kthread+0x3b5/0x4a0 kernel/kthread.c:291 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.8.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:advance_sched+0x455/0x990 net/sched/sch_taprio.c:747 Code: 08 84 d2 0f 85 99 04 00 00 41 89 6c 24 20 e8 72 be 10 fb 48 b8 00 00 00 00 00 fc ff df 48 8b 54 24 08 48 c1 ea 03 80 3c 02 00 <0f> 85 4c 04 00 00 48 8b 7c 24 18 4c 89 63 e8 e8 d7 64 85 01 48 8d RSP: 0018:ffffc90000007d78 EFLAGS: 00000046 RAX: dffffc0000000000 RBX: ffff88809dc04b40 RCX: ffffffff8662fdea RDX: 1ffff11013b80965 RSI: ffffffff8662fe1e RDI: ffff8880a74c71a0 RBP: 0000000000000a00 R08: 0000000000000001 R09: ffff8880a74c71a3 R10: ffffed1014e98e34 R11: 0000000000000000 R12: ffff8880a74c7180 R13: 1623e9f81cc16400 R14: ffff8880a74c71a0 R15: 1623e9f81cc16400 FS: 0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000080a8270 CR3: 0000000009a79000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <IRQ> __run_hrtimer kernel/time/hrtimer.c:1520 [inline] __hrtimer_run_queues+0x6a9/0xfc0 kernel/time/hrtimer.c:1584 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1646 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline] __sysvec_apic_timer_interrupt+0x142/0x5e0 arch/x86/kernel/apic/apic.c:1097 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711 </IRQ> __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline] sysvec_apic_timer_interrupt+0xe0/0x120 arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585 RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61 Code: ff 4c 89 ef e8 53 c8 ca f9 e9 8e fe ff ff 48 89 df e8 46 c8 ca f9 eb 8a cc cc cc cc e9 07 00 00 00 0f 00 2d 74 5f 60 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 64 5f 60 00 f4 c3 cc cc 55 53 e8 29 RSP: 0018:ffffffff89a07c70 EFLAGS: 00000293 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffffffff89a86580 RSI: ffffffff87e85c48 RDI: ffffffff87e85c1e RBP: ffff8880a7120064 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff8880a7120064 R13: 1ffffffff1340f98 R14: ffff8880a7120065 R15: 0000000000000001 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline] acpi_safe_halt+0x8d/0x110 drivers/acpi/processor_idle.c:111 acpi_idle_do_entry+0x15c/0x1b0 drivers/acpi/processor_idle.c:525 acpi_idle_enter+0x3f9/0xab0 drivers/acpi/processor_idle.c:651 cpuidle_enter_state+0xff/0x960 drivers/cpuidle/cpuidle.c:235 cpuidle_enter+0x4a/0xa0 drivers/cpuidle/cpuidle.c:346 call_cpuidle kernel/sched/idle.c:126 [inline] cpuidle_idle_call kernel/sched/idle.c:214 [inline] do_idle+0x431/0x6d0 kernel/sched/idle.c:276 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:372 start_kernel+0x9cb/0xa06 init/main.c:1043 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 --- This report is generated by a bot. 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