linux-kernel - Re: possible deadlock in __wake_up_common

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Date:   Wed, 2 Jan 2019 13:51:01 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     syzbot <syzbot+93d94a001cfbce9e60e1@...kaller.appspotmail.com>,
        aarcange@...hat.com, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux@...inikbrodowski.net, mhocko@...e.com,
        rientjes@...gle.com, syzkaller-bugs@...glegroups.com,
        xieyisheng1@...wei.com, zhongjiang@...wei.com,
        Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: possible deadlock in __wake_up_common_lock

On 1/2/19 9:51 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    f346b0becb1b Merge branch 'akpm' (patches from Andrew)
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1510cefd400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c255c77ba370fe7c
> dashboard link: https://syzkaller.appspot.com/bug?extid=93d94a001cfbce9e60e1
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+93d94a001cfbce9e60e1@...kaller.appspotmail.com
> 
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 4.20.0+ #297 Not tainted
> ------------------------------------------------------
> syz-executor0/8529 is trying to acquire lock:
> 000000005e7fb829 (&pgdat->kswapd_wait){....}, at:  
> __wake_up_common_lock+0x19e/0x330 kernel/sched/wait.c:120

>From the backtrace at the end of report I see it's coming from

>   wakeup_kswapd+0x5f0/0x930 mm/vmscan.c:3982
>   steal_suitable_fallback+0x538/0x830 mm/page_alloc.c:2217

This wakeup_kswapd is new due to Mel's 1c30844d2dfe ("mm: reclaim small
amounts of memory when an external fragmentation event occurs") so CC Mel.

> but task is already holding lock:
> 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: spin_lock  
> include/linux/spinlock.h:329 [inline]
> 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: rmqueue_bulk  
> mm/page_alloc.c:2548 [inline]
> 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: __rmqueue_pcplist  
> mm/page_alloc.c:3021 [inline]
> 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: rmqueue_pcplist  
> mm/page_alloc.c:3050 [inline]
> 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: rmqueue  
> mm/page_alloc.c:3072 [inline]
> 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at:  
> get_page_from_freelist+0x1bae/0x52a0 mm/page_alloc.c:3491
> 
> which lock already depends on the new lock.

However, I don't understand why lockdep thinks it's a problem. IIRC it
doesn't like that we are locking pgdat->kswapd_wait.lock while holding
zone->lock. That means it has learned that the opposite order also
exists, e.g. somebody would take zone->lock while manipulating the wait
queue? I don't see where but I admit I'm not good at reading lockdep
splats, so CCing Peterz and Ingo as well. Keeping rest of mail for
reference.

> the existing dependency chain (in reverse order) is:
> 
> -> #4 (&(&zone->lock)->rlock){-.-.}:
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>         rmqueue mm/page_alloc.c:3082 [inline]
>         get_page_from_freelist+0x9eb/0x52a0 mm/page_alloc.c:3491
>         __alloc_pages_nodemask+0x4f3/0xde0 mm/page_alloc.c:4529
>         __alloc_pages include/linux/gfp.h:473 [inline]
>         alloc_page_interleave+0x25/0x1c0 mm/mempolicy.c:1988
>         alloc_pages_current+0x1bf/0x210 mm/mempolicy.c:2104
>         alloc_pages include/linux/gfp.h:509 [inline]
>         depot_save_stack+0x3f1/0x470 lib/stackdepot.c:260
>         save_stack+0xa9/0xd0 mm/kasan/common.c:79
>         set_track mm/kasan/common.c:85 [inline]
>         kasan_kmalloc+0xcb/0xd0 mm/kasan/common.c:482
>         kasan_slab_alloc+0x12/0x20 mm/kasan/common.c:397
>         kmem_cache_alloc+0x130/0x730 mm/slab.c:3541
>         kmem_cache_zalloc include/linux/slab.h:731 [inline]
>         fill_pool lib/debugobjects.c:134 [inline]
>         __debug_object_init+0xbb8/0x1290 lib/debugobjects.c:379
>         debug_object_init lib/debugobjects.c:431 [inline]
>         debug_object_activate+0x323/0x600 lib/debugobjects.c:512
>         debug_timer_activate kernel/time/timer.c:708 [inline]
>         debug_activate kernel/time/timer.c:763 [inline]
>         __mod_timer kernel/time/timer.c:1040 [inline]
>         mod_timer kernel/time/timer.c:1101 [inline]
>         add_timer+0x50e/0x1490 kernel/time/timer.c:1137
>         __queue_delayed_work+0x249/0x380 kernel/workqueue.c:1533
>         queue_delayed_work_on+0x1a2/0x1f0 kernel/workqueue.c:1558
>         queue_delayed_work include/linux/workqueue.h:527 [inline]
>         schedule_delayed_work include/linux/workqueue.h:628 [inline]
>         start_dirtytime_writeback+0x4e/0x53 fs/fs-writeback.c:2043
>         do_one_initcall+0x145/0x957 init/main.c:889
>         do_initcall_level init/main.c:957 [inline]
>         do_initcalls init/main.c:965 [inline]
>         do_basic_setup init/main.c:983 [inline]
>         kernel_init_freeable+0x4c1/0x5af init/main.c:1136
>         kernel_init+0x11/0x1ae init/main.c:1056
>         ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
> 
> -> #3 (&base->lock){-.-.}:
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>         lock_timer_base+0xbb/0x2b0 kernel/time/timer.c:937
>         __mod_timer kernel/time/timer.c:1009 [inline]
>         mod_timer kernel/time/timer.c:1101 [inline]
>         add_timer+0x895/0x1490 kernel/time/timer.c:1137
>         __queue_delayed_work+0x249/0x380 kernel/workqueue.c:1533
>         queue_delayed_work_on+0x1a2/0x1f0 kernel/workqueue.c:1558
>         queue_delayed_work include/linux/workqueue.h:527 [inline]
>         schedule_delayed_work include/linux/workqueue.h:628 [inline]
>         psi_group_change kernel/sched/psi.c:485 [inline]
>         psi_task_change+0x3f1/0x5f0 kernel/sched/psi.c:534
>         psi_enqueue kernel/sched/stats.h:82 [inline]
>         enqueue_task kernel/sched/core.c:727 [inline]
>         activate_task+0x21a/0x430 kernel/sched/core.c:751
>         wake_up_new_task+0x527/0xd20 kernel/sched/core.c:2423
>         _do_fork+0x33b/0x11d0 kernel/fork.c:2247
>         kernel_thread+0x34/0x40 kernel/fork.c:2281
>         rest_init+0x28/0x372 init/main.c:409
>         arch_call_rest_init+0xe/0x1b
>         start_kernel+0x873/0x8ae init/main.c:741
>         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
> 
> -> #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:1149 [inline]
>         task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:10083
>         sched_fork+0x443/0xba0 kernel/sched/core.c:2359
>         copy_process+0x25b9/0x8790 kernel/fork.c:1893
>         _do_fork+0x1cb/0x11d0 kernel/fork.c:2222
>         kernel_thread+0x34/0x40 kernel/fork.c:2281
>         rest_init+0x28/0x372 init/main.c:409
>         arch_call_rest_init+0xe/0x1b
>         start_kernel+0x873/0x8ae init/main.c:741
>         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+0xdc/0x1460 kernel/sched/core.c:1965
>         default_wake_function+0x30/0x50 kernel/sched/core.c:3710
>         autoremove_wake_function+0x80/0x370 kernel/sched/wait.c:375
>         __wake_up_common+0x1d7/0x7d0 kernel/sched/wait.c:92
>         __wake_up_common_lock+0x1c2/0x330 kernel/sched/wait.c:121
>         __wake_up+0xe/0x10 kernel/sched/wait.c:145
>         wakeup_kswapd+0x5f0/0x930 mm/vmscan.c:3982
>         wake_all_kswapds+0x150/0x300 mm/page_alloc.c:3975
>         __alloc_pages_slowpath+0x1ff1/0x2db0 mm/page_alloc.c:4246
>         __alloc_pages_nodemask+0xa89/0xde0 mm/page_alloc.c:4549
>         alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2106
>         alloc_pages include/linux/gfp.h:509 [inline]
>         __get_free_pages+0xc/0x40 mm/page_alloc.c:4573
>         pte_alloc_one_kernel+0x15/0x20 arch/x86/mm/pgtable.c:28
>         __pte_alloc_kernel+0x23/0x220 mm/memory.c:439
>         vmap_pte_range mm/vmalloc.c:144 [inline]
>         vmap_pmd_range mm/vmalloc.c:171 [inline]
>         vmap_pud_range mm/vmalloc.c:188 [inline]
>         vmap_p4d_range mm/vmalloc.c:205 [inline]
>         vmap_page_range_noflush+0x878/0xa80 mm/vmalloc.c:230
>         vmap_page_range mm/vmalloc.c:243 [inline]
>         vm_map_ram+0x46c/0xf60 mm/vmalloc.c:1181
>         ion_heap_clear_pages+0x2a/0x70  
> drivers/staging/android/ion/ion_heap.c:100
>         ion_heap_sglist_zero+0x24f/0x2d0  
> drivers/staging/android/ion/ion_heap.c:121
>         ion_heap_buffer_zero+0xf8/0x150  
> drivers/staging/android/ion/ion_heap.c:143
>         ion_system_heap_free+0x227/0x290  
> drivers/staging/android/ion/ion_system_heap.c:163
>         ion_buffer_destroy+0x15c/0x1c0 drivers/staging/android/ion/ion.c:119
>         _ion_heap_freelist_drain+0x43e/0x6a0  
> drivers/staging/android/ion/ion_heap.c:199
>         ion_heap_freelist_drain+0x1f/0x30  
> drivers/staging/android/ion/ion_heap.c:209
>         ion_buffer_create drivers/staging/android/ion/ion.c:86 [inline]
>         ion_alloc+0x487/0xa60 drivers/staging/android/ion/ion.c:409
>         ion_ioctl+0x216/0x41e drivers/staging/android/ion/ion-ioctl.c:76
>         __do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline]
>         __se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline]
>         __ia32_compat_sys_ioctl+0x20e/0x630 fs/compat_ioctl.c:998
>         do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
>         do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397
>         entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
> 
> -> #0 (&pgdat->kswapd_wait){....}:
>         lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841
>         __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>         _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>         __wake_up_common_lock+0x19e/0x330 kernel/sched/wait.c:120
>         __wake_up+0xe/0x10 kernel/sched/wait.c:145
>         wakeup_kswapd+0x5f0/0x930 mm/vmscan.c:3982
>         steal_suitable_fallback+0x538/0x830 mm/page_alloc.c:2217
>         __rmqueue_fallback mm/page_alloc.c:2502 [inline]
>         __rmqueue mm/page_alloc.c:2528 [inline]
>         rmqueue_bulk mm/page_alloc.c:2550 [inline]
>         __rmqueue_pcplist mm/page_alloc.c:3021 [inline]
>         rmqueue_pcplist mm/page_alloc.c:3050 [inline]
>         rmqueue mm/page_alloc.c:3072 [inline]
>         get_page_from_freelist+0x318c/0x52a0 mm/page_alloc.c:3491
>         __alloc_pages_nodemask+0x4f3/0xde0 mm/page_alloc.c:4529
>         alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2106
>         alloc_pages include/linux/gfp.h:509 [inline]
>         __get_free_pages+0xc/0x40 mm/page_alloc.c:4573
>         tlb_next_batch mm/mmu_gather.c:29 [inline]
>         __tlb_remove_page_size+0x2e5/0x500 mm/mmu_gather.c:133
>         __tlb_remove_page include/asm-generic/tlb.h:187 [inline]
>         zap_pte_range mm/memory.c:1093 [inline]
>         zap_pmd_range mm/memory.c:1192 [inline]
>         zap_pud_range mm/memory.c:1221 [inline]
>         zap_p4d_range mm/memory.c:1242 [inline]
>         unmap_page_range+0xf88/0x25b0 mm/memory.c:1263
>         unmap_single_vma+0x19b/0x310 mm/memory.c:1308
>         unmap_vmas+0x221/0x390 mm/memory.c:1339
>         exit_mmap+0x2be/0x590 mm/mmap.c:3140
>         __mmput kernel/fork.c:1051 [inline]
>         mmput+0x247/0x610 kernel/fork.c:1072
>         exit_mm kernel/exit.c:545 [inline]
>         do_exit+0xdeb/0x2620 kernel/exit.c:854
>         do_group_exit+0x177/0x440 kernel/exit.c:970
>         get_signal+0x8b0/0x1980 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_32_irqs_on arch/x86/entry/common.c:341 [inline]
>         do_fast_syscall_32+0xcd5/0xfb2 arch/x86/entry/common.c:397
>         entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
> 
> other info that might help us debug this:
> 
> Chain exists of:
>    &pgdat->kswapd_wait --> &base->lock --> &(&zone->lock)->rlock
> 
>   Possible unsafe locking scenario:
> 
>         CPU0                    CPU1
>         ----                    ----
>    lock(&(&zone->lock)->rlock);
>                                 lock(&base->lock);
>                                 lock(&(&zone->lock)->rlock);
>    lock(&pgdat->kswapd_wait);
> 
>   *** DEADLOCK ***
> 
> 2 locks held by syz-executor0/8529:
>   #0: 000000001be7b4ca (&(ptlock_ptr(page))->rlock#2){+.+.}, at: spin_lock  
> include/linux/spinlock.h:329 [inline]
>   #0: 000000001be7b4ca (&(ptlock_ptr(page))->rlock#2){+.+.}, at:  
> zap_pte_range mm/memory.c:1051 [inline]
>   #0: 000000001be7b4ca (&(ptlock_ptr(page))->rlock#2){+.+.}, at:  
> zap_pmd_range mm/memory.c:1192 [inline]
>   #0: 000000001be7b4ca (&(ptlock_ptr(page))->rlock#2){+.+.}, at:  
> zap_pud_range mm/memory.c:1221 [inline]
>   #0: 000000001be7b4ca (&(ptlock_ptr(page))->rlock#2){+.+.}, at:  
> zap_p4d_range mm/memory.c:1242 [inline]
>   #0: 000000001be7b4ca (&(ptlock_ptr(page))->rlock#2){+.+.}, at:  
> unmap_page_range+0x98e/0x25b0 mm/memory.c:1263
>   #1: 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: spin_lock  
> include/linux/spinlock.h:329 [inline]
>   #1: 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: rmqueue_bulk  
> mm/page_alloc.c:2548 [inline]
>   #1: 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: __rmqueue_pcplist  
> mm/page_alloc.c:3021 [inline]
>   #1: 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: rmqueue_pcplist  
> mm/page_alloc.c:3050 [inline]
>   #1: 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at: rmqueue  
> mm/page_alloc.c:3072 [inline]
>   #1: 000000009bb7bae0 (&(&zone->lock)->rlock){-.-.}, at:  
> get_page_from_freelist+0x1bae/0x52a0 mm/page_alloc.c:3491
> 
> stack backtrace:
> CPU: 0 PID: 8529 Comm: syz-executor0 Not tainted 4.20.0+ #297
> 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+0x1d3/0x2c6 lib/dump_stack.c:113
>   print_circular_bug.isra.34.cold.56+0x1bd/0x27d  
> kernel/locking/lockdep.c:1224
>   check_prev_add kernel/locking/lockdep.c:1866 [inline]
>   check_prevs_add kernel/locking/lockdep.c:1979 [inline]
>   validate_chain kernel/locking/lockdep.c:2350 [inline]
>   __lock_acquire+0x3360/0x4c20 kernel/locking/lockdep.c:3338
>   lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841
>   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>   _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>   __wake_up_common_lock+0x19e/0x330 kernel/sched/wait.c:120
>   __wake_up+0xe/0x10 kernel/sched/wait.c:145
>   wakeup_kswapd+0x5f0/0x930 mm/vmscan.c:3982
>   steal_suitable_fallback+0x538/0x830 mm/page_alloc.c:2217
>   __rmqueue_fallback mm/page_alloc.c:2502 [inline]
>   __rmqueue mm/page_alloc.c:2528 [inline]
>   rmqueue_bulk mm/page_alloc.c:2550 [inline]
>   __rmqueue_pcplist mm/page_alloc.c:3021 [inline]
>   rmqueue_pcplist mm/page_alloc.c:3050 [inline]
>   rmqueue mm/page_alloc.c:3072 [inline]
>   get_page_from_freelist+0x318c/0x52a0 mm/page_alloc.c:3491
>   __alloc_pages_nodemask+0x4f3/0xde0 mm/page_alloc.c:4529
>   alloc_pages_current+0x10c/0x210 mm/mempolicy.c:2106
>   alloc_pages include/linux/gfp.h:509 [inline]
>   __get_free_pages+0xc/0x40 mm/page_alloc.c:4573
>   tlb_next_batch mm/mmu_gather.c:29 [inline]
>   __tlb_remove_page_size+0x2e5/0x500 mm/mmu_gather.c:133
>   __tlb_remove_page include/asm-generic/tlb.h:187 [inline]
>   zap_pte_range mm/memory.c:1093 [inline]
>   zap_pmd_range mm/memory.c:1192 [inline]
>   zap_pud_range mm/memory.c:1221 [inline]
>   zap_p4d_range mm/memory.c:1242 [inline]
>   unmap_page_range+0xf88/0x25b0 mm/memory.c:1263
>   unmap_single_vma+0x19b/0x310 mm/memory.c:1308
>   unmap_vmas+0x221/0x390 mm/memory.c:1339
>   exit_mmap+0x2be/0x590 mm/mmap.c:3140
>   __mmput kernel/fork.c:1051 [inline]
>   mmput+0x247/0x610 kernel/fork.c:1072
>   exit_mm kernel/exit.c:545 [inline]
>   do_exit+0xdeb/0x2620 kernel/exit.c:854
>   do_group_exit+0x177/0x440 kernel/exit.c:970
>   get_signal+0x8b0/0x1980 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_32_irqs_on arch/x86/entry/common.c:341 [inline]
>   do_fast_syscall_32+0xcd5/0xfb2 arch/x86/entry/common.c:397
>   entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
> RIP: 0023:0xf7fe3849
> Code: Bad RIP value.
> RSP: 002b:00000000f5f9d0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
> RAX: 0000000000000000 RBX: 0000000000000005 RCX: 00000000c0184900
> RDX: 0000000020000080 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> syz-executor0 (8529) used greatest stack depth: 10424 bytes left
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> audit: type=1326 audit(1546069676.863:33): auid=4294967295 uid=0 gid=0  
> ses=4294967295 subj==unconfined pid=8664 comm="syz-executor1"  
> exe="/root/syz-executor1" sig=31 arch=40000003 syscall=265 compat=1  
> ip=0xf7f82849 code=0x0
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop5' (00000000c7588ca8): kobject_uevent_env
> kobject: 'loop5' (00000000c7588ca8): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop4' (00000000ebe25695): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop4' (00000000ebe25695): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop0' (000000002925f66c): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop0' (000000002925f66c): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): kobject_uevent_env
> kobject: 'loop3' (0000000061a5b8df): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'kvm' (00000000eddbbf94): kobject_uevent_env
> kobject: 'kvm' (00000000eddbbf94): fill_kobj_path: path  
> = '/devices/virtual/misc/kvm'
> kobject: 'loop1' (0000000003dfbc9f): kobject_uevent_env
> kobject: 'loop1' (0000000003dfbc9f): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop2' (00000000c253515f): kobject_uevent_env
> kobject: 'loop2' (00000000c253515f): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> WARNING: CPU: 0 PID: 8908 at net/bridge/netfilter/ebtables.c:2086  
> ebt_size_mwt net/bridge/netfilter/ebtables.c:2086 [inline]
> WARNING: CPU: 0 PID: 8908 at net/bridge/netfilter/ebtables.c:2086  
> size_entry_mwt net/bridge/netfilter/ebtables.c:2167 [inline]
> WARNING: CPU: 0 PID: 8908 at net/bridge/netfilter/ebtables.c:2086  
> compat_copy_entries+0x1088/0x1500 net/bridge/netfilter/ebtables.c:2206
> 
> 
> ---
> 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.
>