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Date: Sun, 9 Sep 2018 12:11:04 -0700
From: Matthew Wilcox <willy@...radead.org>
To: syzbot <syzbot+d86c4426a01f60feddc7@...kaller.appspotmail.com>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>,
Miklos Szeredi <mszeredi@...hat.com>,
Kirill Tkhai <ktkhai@...tuozzo.com>, bcrl@...ck.org,
linux-aio@...ck.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
viro@...iv.linux.org.uk
Subject: Re: possible deadlock in free_ioctx_users
I would be inclined to blame FUSE for this problem.
On Sun, Sep 09, 2018 at 11:41:02AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: f8f65382c98a Merge tag 'for-linus' of git://git.kernel.org..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=113260ae400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
> dashboard link: https://syzkaller.appspot.com/bug?extid=d86c4426a01f60feddc7
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=120baa9e400000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13979cbe400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+d86c4426a01f60feddc7@...kaller.appspotmail.com
>
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
> random: sshd: uninitialized urandom read (32 bytes read)
>
> ========================================================
> WARNING: possible irq lock inversion dependency detected
> 4.19.0-rc2+ #229 Not tainted
> --------------------------------------------------------
> swapper/0/0 just changed the state of lock:
> 00000000c02bddef (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq
> include/linux/spinlock.h:354 [inline]
> 00000000c02bddef (&(&ctx->ctx_lock)->rlock){..-.}, at:
> free_ioctx_users+0xbc/0x710 fs/aio.c:603
> but this lock took another, SOFTIRQ-unsafe lock in the past:
> (&fiq->waitq){+.+.}
>
>
> and interrupts could create inverse lock ordering between them.
>
>
> other info that might help us debug this:
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1
> ---- ----
> lock(&fiq->waitq);
> local_irq_disable();
> lock(&(&ctx->ctx_lock)->rlock);
> lock(&fiq->waitq);
> <Interrupt>
> lock(&(&ctx->ctx_lock)->rlock);
>
> *** DEADLOCK ***
>
> 2 locks held by swapper/0/0:
> #0: 0000000077c9a56b (rcu_callback){....}, at: __rcu_reclaim
> kernel/rcu/rcu.h:226 [inline]
> #0: 0000000077c9a56b (rcu_callback){....}, at: rcu_do_batch
> kernel/rcu/tree.c:2576 [inline]
> #0: 0000000077c9a56b (rcu_callback){....}, at: invoke_rcu_callbacks
> kernel/rcu/tree.c:2880 [inline]
> #0: 0000000077c9a56b (rcu_callback){....}, at: __rcu_process_callbacks
> kernel/rcu/tree.c:2847 [inline]
> #0: 0000000077c9a56b (rcu_callback){....}, at:
> rcu_process_callbacks+0x1012/0x2670 kernel/rcu/tree.c:2864
> #1: 0000000031dcf310 (rcu_read_lock_sched){....}, at:
> percpu_ref_call_confirm_rcu lib/percpu-refcount.c:119 [inline]
> #1: 0000000031dcf310 (rcu_read_lock_sched){....}, at:
> percpu_ref_switch_to_atomic_rcu+0x2b7/0x820 lib/percpu-refcount.c:158
>
> the shortest dependencies between 2nd lock and 1st lock:
> -> (&fiq->waitq){+.+.} ops: 4 {
> HARDIRQ-ON-W at:
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock include/linux/spinlock_api_smp.h:142
> [inline]
> _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
> spin_lock include/linux/spinlock.h:329 [inline]
> flush_bg_queue+0x389/0x650 fs/fuse/dev.c:364
> fuse_request_send_background_locked+0x2f5/0x5a0
> fs/fuse/dev.c:598
> fuse_request_send_background+0x135/0x180
> fs/fuse/dev.c:606
> cuse_send_init fs/fuse/cuse.c:458 [inline]
> cuse_channel_open+0x6b0/0x963 fs/fuse/cuse.c:518
> misc_open+0x3ca/0x560 drivers/char/misc.c:141
> chrdev_open+0x25a/0x710 fs/char_dev.c:417
> do_dentry_open+0x499/0x1250 fs/open.c:771
> vfs_open+0xa0/0xd0 fs/open.c:880
> do_last fs/namei.c:3418 [inline]
> path_openat+0x12bf/0x5160 fs/namei.c:3534
> do_filp_open+0x255/0x380 fs/namei.c:3564
> do_sys_open+0x568/0x700 fs/open.c:1063
> __do_sys_openat fs/open.c:1090 [inline]
> __se_sys_openat fs/open.c:1084 [inline]
> __x64_sys_openat+0x9d/0x100 fs/open.c:1084
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> SOFTIRQ-ON-W at:
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock include/linux/spinlock_api_smp.h:142
> [inline]
> _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
> spin_lock include/linux/spinlock.h:329 [inline]
> flush_bg_queue+0x389/0x650 fs/fuse/dev.c:364
> fuse_request_send_background_locked+0x2f5/0x5a0
> fs/fuse/dev.c:598
> fuse_request_send_background+0x135/0x180
> fs/fuse/dev.c:606
> cuse_send_init fs/fuse/cuse.c:458 [inline]
> cuse_channel_open+0x6b0/0x963 fs/fuse/cuse.c:518
> misc_open+0x3ca/0x560 drivers/char/misc.c:141
> chrdev_open+0x25a/0x710 fs/char_dev.c:417
> do_dentry_open+0x499/0x1250 fs/open.c:771
> vfs_open+0xa0/0xd0 fs/open.c:880
> do_last fs/namei.c:3418 [inline]
> path_openat+0x12bf/0x5160 fs/namei.c:3534
> do_filp_open+0x255/0x380 fs/namei.c:3564
> do_sys_open+0x568/0x700 fs/open.c:1063
> __do_sys_openat fs/open.c:1090 [inline]
> __se_sys_openat fs/open.c:1084 [inline]
> __x64_sys_openat+0x9d/0x100 fs/open.c:1084
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> INITIAL USE at:
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock include/linux/spinlock_api_smp.h:142
> [inline]
> _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
> spin_lock include/linux/spinlock.h:329 [inline]
> flush_bg_queue+0x389/0x650 fs/fuse/dev.c:364
> fuse_request_send_background_locked+0x2f5/0x5a0
> fs/fuse/dev.c:598
> fuse_request_send_background+0x135/0x180
> fs/fuse/dev.c:606
> cuse_send_init fs/fuse/cuse.c:458 [inline]
> cuse_channel_open+0x6b0/0x963 fs/fuse/cuse.c:518
> misc_open+0x3ca/0x560 drivers/char/misc.c:141
> chrdev_open+0x25a/0x710 fs/char_dev.c:417
> do_dentry_open+0x499/0x1250 fs/open.c:771
> vfs_open+0xa0/0xd0 fs/open.c:880
> do_last fs/namei.c:3418 [inline]
> path_openat+0x12bf/0x5160 fs/namei.c:3534
> do_filp_open+0x255/0x380 fs/namei.c:3564
> do_sys_open+0x568/0x700 fs/open.c:1063
> __do_sys_openat fs/open.c:1090 [inline]
> __se_sys_openat fs/open.c:1084 [inline]
> __x64_sys_openat+0x9d/0x100 fs/open.c:1084
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> }
> ... key at: [<ffffffff8b4763c0>] __key.42168+0x0/0x40
> ... acquired at:
> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
> _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
> spin_lock include/linux/spinlock.h:329 [inline]
> aio_poll+0x760/0x1420 fs/aio.c:1747
> io_submit_one+0xab8/0x1090 fs/aio.c:1850
> __do_sys_io_submit fs/aio.c:1916 [inline]
> __se_sys_io_submit fs/aio.c:1887 [inline]
> __x64_sys_io_submit+0x1b9/0x5d0 fs/aio.c:1887
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> -> (&(&ctx->ctx_lock)->rlock){..-.} ops: 2 {
> IN-SOFTIRQ-W at:
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128
> [inline]
> _raw_spin_lock_irq+0x61/0x80
> kernel/locking/spinlock.c:160
> spin_lock_irq include/linux/spinlock.h:354 [inline]
> free_ioctx_users+0xbc/0x710 fs/aio.c:603
> percpu_ref_put_many include/linux/percpu-refcount.h:284
> [inline]
> percpu_ref_put include/linux/percpu-refcount.h:300
> [inline]
> percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123
> [inline]
> percpu_ref_switch_to_atomic_rcu+0x62c/0x820
> lib/percpu-refcount.c:158
> __rcu_reclaim kernel/rcu/rcu.h:236 [inline]
> rcu_do_batch kernel/rcu/tree.c:2576 [inline]
> invoke_rcu_callbacks kernel/rcu/tree.c:2880 [inline]
> __rcu_process_callbacks kernel/rcu/tree.c:2847 [inline]
> rcu_process_callbacks+0xf23/0x2670
> kernel/rcu/tree.c:2864
> __do_softirq+0x30b/0xad8 kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:372 [inline]
> irq_exit+0x17f/0x1c0 kernel/softirq.c:412
> exiting_irq arch/x86/include/asm/apic.h:536 [inline]
> smp_apic_timer_interrupt+0x1cb/0x760
> arch/x86/kernel/apic/apic.c:1056
> apic_timer_interrupt+0xf/0x20
> arch/x86/entry/entry_64.S:864
> native_safe_halt+0x6/0x10
> arch/x86/include/asm/irqflags.h:57
> arch_safe_halt arch/x86/include/asm/paravirt.h:94
> [inline]
> default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
> arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
> default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
> cpuidle_idle_call kernel/sched/idle.c:153 [inline]
> do_idle+0x3db/0x5b0 kernel/sched/idle.c:262
> cpu_startup_entry+0x10c/0x120 kernel/sched/idle.c:368
> rest_init+0xe2/0xe5 init/main.c:442
> start_kernel+0x8f4/0x92f init/main.c:739
> x86_64_start_reservations+0x29/0x2b
> arch/x86/kernel/head64.c:452
> x86_64_start_kernel+0x76/0x79
> arch/x86/kernel/head64.c:433
> secondary_startup_64+0xa4/0xb0
> arch/x86/kernel/head_64.S:242
> INITIAL USE at:
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128
> [inline]
> _raw_spin_lock_irq+0x61/0x80
> kernel/locking/spinlock.c:160
> spin_lock_irq include/linux/spinlock.h:354 [inline]
> aio_poll+0x738/0x1420 fs/aio.c:1746
> io_submit_one+0xab8/0x1090 fs/aio.c:1850
> __do_sys_io_submit fs/aio.c:1916 [inline]
> __se_sys_io_submit fs/aio.c:1887 [inline]
> __x64_sys_io_submit+0x1b9/0x5d0 fs/aio.c:1887
> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
> entry_SYSCALL_64_after_hwframe+0x49/0xbe
> }
> ... key at: [<ffffffff8b3dc960>] __key.50120+0x0/0x40
> ... acquired at:
> mark_lock_irq kernel/locking/lockdep.c:2756 [inline]
> mark_lock+0xa6b/0x1cb0 kernel/locking/lockdep.c:3128
> mark_irqflags kernel/locking/lockdep.c:3006 [inline]
> __lock_acquire+0x15f8/0x4ec0 kernel/locking/lockdep.c:3369
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
> _raw_spin_lock_irq+0x61/0x80 kernel/locking/spinlock.c:160
> spin_lock_irq include/linux/spinlock.h:354 [inline]
> free_ioctx_users+0xbc/0x710 fs/aio.c:603
> percpu_ref_put_many include/linux/percpu-refcount.h:284 [inline]
> percpu_ref_put include/linux/percpu-refcount.h:300 [inline]
> percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
> percpu_ref_switch_to_atomic_rcu+0x62c/0x820 lib/percpu-refcount.c:158
> __rcu_reclaim kernel/rcu/rcu.h:236 [inline]
> rcu_do_batch kernel/rcu/tree.c:2576 [inline]
> invoke_rcu_callbacks kernel/rcu/tree.c:2880 [inline]
> __rcu_process_callbacks kernel/rcu/tree.c:2847 [inline]
> rcu_process_callbacks+0xf23/0x2670 kernel/rcu/tree.c:2864
> __do_softirq+0x30b/0xad8 kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:372 [inline]
> irq_exit+0x17f/0x1c0 kernel/softirq.c:412
> exiting_irq arch/x86/include/asm/apic.h:536 [inline]
> smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1056
> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
> native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57
> arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
> default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
> arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
> default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
> cpuidle_idle_call kernel/sched/idle.c:153 [inline]
> do_idle+0x3db/0x5b0 kernel/sched/idle.c:262
> cpu_startup_entry+0x10c/0x120 kernel/sched/idle.c:368
> rest_init+0xe2/0xe5 init/main.c:442
> start_kernel+0x8f4/0x92f init/main.c:739
> x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:452
> x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:433
> secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242
>
>
> stack backtrace:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0-rc2+ #229
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> <IRQ>
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
> print_irq_inversion_bug.part.35+0x2c7/0x2d6 kernel/locking/lockdep.c:2622
> print_irq_inversion_bug kernel/locking/lockdep.c:2625 [inline]
> check_usage_forwards.cold.57+0x20/0x29 kernel/locking/lockdep.c:2647
> mark_lock_irq kernel/locking/lockdep.c:2756 [inline]
> mark_lock+0xa6b/0x1cb0 kernel/locking/lockdep.c:3128
> mark_irqflags kernel/locking/lockdep.c:3006 [inline]
> __lock_acquire+0x15f8/0x4ec0 kernel/locking/lockdep.c:3369
> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3901
> __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
> _raw_spin_lock_irq+0x61/0x80 kernel/locking/spinlock.c:160
> spin_lock_irq include/linux/spinlock.h:354 [inline]
> free_ioctx_users+0xbc/0x710 fs/aio.c:603
> percpu_ref_put_many include/linux/percpu-refcount.h:284 [inline]
> percpu_ref_put include/linux/percpu-refcount.h:300 [inline]
> percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
> percpu_ref_switch_to_atomic_rcu+0x62c/0x820 lib/percpu-refcount.c:158
> __rcu_reclaim kernel/rcu/rcu.h:236 [inline]
> rcu_do_batch kernel/rcu/tree.c:2576 [inline]
> invoke_rcu_callbacks kernel/rcu/tree.c:2880 [inline]
> __rcu_process_callbacks kernel/rcu/tree.c:2847 [inline]
> rcu_process_callbacks+0xf23/0x2670 kernel/rcu/tree.c:2864
> __do_softirq+0x30b/0xad8 kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:372 [inline]
> irq_exit+0x17f/0x1c0 kernel/softirq.c:412
> exiting_irq arch/x86/include/asm/apic.h:536 [inline]
> smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1056
> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:864
> </IRQ>
> RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57
> Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 43 b9 02 fa 48 8b 45 d8 e9 ca
> fe ff ff 48 89 df e8 32 b9 02 fa eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00
> 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90
> RSP: 0018:ffffffff89407bb8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
> RAX: dffffc0000000000 RBX: 1ffffffff1280f7b RCX: 0000000000000000
> RDX: 1ffffffff12a4538 RSI: 0000000000000001 RDI: ffffffff895229c0
> RBP: ffffffff89407bb8 R08: ffffffff89475fc0 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89407c78
> R13: ffffffff8a3149a0 R14: 0000000000000000 R15: 0000000000000000
> arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
> default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
> arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
> default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
> cpuidle_idle_call kernel/sched/idle.c:153 [inline]
> do_idle+0x3db/0x5b0 kernel/sched/idle.c:262
> cpu_startup_entry+0x10c/0x120 kernel/sched/idle.c:368
> rest_init+0xe2/0xe5 init/main.c:442
> start_kernel+0x8f4/0x92f init/main.c:739
> ? early_idt_handler_common+
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
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