linux-kernel - Re: possible deadlock in __do_page

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Message-Id: <20180920141058.4ed467594761e073606eafe2@linux-foundation.org>
Date:   Thu, 20 Sep 2018 14:10:58 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     syzbot <syzbot+a76129f18c89f3e2ddd4@...kaller.appspotmail.com>
Cc:     ak@...ux.intel.com, hannes@...xchg.org, jack@...e.cz,
        jrdr.linux@...il.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, mawilcox@...rosoft.com,
        mgorman@...hsingularity.net, syzkaller-bugs@...glegroups.com,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>
Subject: Re: possible deadlock in __do_page_fault


Thanks.  Let's cc the ashmem folks.

On Thu, 20 Sep 2018 14:04:05 -0700 syzbot <syzbot+a76129f18c89f3e2ddd4@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    a0cb0cabe4bb Add linux-next specific files for 20180920
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15139721400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=786006c5dafbadf6
> dashboard link: https://syzkaller.appspot.com/bug?extid=a76129f18c89f3e2ddd4
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> 
> 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+a76129f18c89f3e2ddd4@...kaller.appspotmail.com
> 
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 4.19.0-rc4-next-20180920+ #76 Not tainted
> ------------------------------------------------------
> syz-executor3/21327 is trying to acquire lock:
> 000000009bc5286f (&mm->mmap_sem){++++}, at: __do_page_fault+0xb61/0xec0  
> arch/x86/mm/fault.c:1333
> 
> but task is already holding lock:
> 00000000a2c51c08 (&sb->s_type->i_mutex_key#10){+.+.}, at: inode_lock  
> include/linux/fs.h:745 [inline]
> 00000000a2c51c08 (&sb->s_type->i_mutex_key#10){+.+.}, at:  
> generic_file_write_iter+0xed/0x870 mm/filemap.c:3304
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #2 (&sb->s_type->i_mutex_key#10){+.+.}:
>         down_write+0x8a/0x130 kernel/locking/rwsem.c:70
>         inode_lock include/linux/fs.h:745 [inline]
>         shmem_fallocate+0x18b/0x12c0 mm/shmem.c:2651
>         ashmem_shrink_scan+0x238/0x660 drivers/staging/android/ashmem.c:455
>         ashmem_ioctl+0x3ae/0x13a0 drivers/staging/android/ashmem.c:797
>         vfs_ioctl fs/ioctl.c:46 [inline]
>         file_ioctl fs/ioctl.c:501 [inline]
>         do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
>         ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
>         __do_sys_ioctl fs/ioctl.c:709 [inline]
>         __se_sys_ioctl fs/ioctl.c:707 [inline]
>         __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
>         do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> -> #1 (ashmem_mutex){+.+.}:
>         __mutex_lock_common kernel/locking/mutex.c:925 [inline]
>         __mutex_lock+0x166/0x1700 kernel/locking/mutex.c:1072
>         mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
>         ashmem_mmap+0x55/0x520 drivers/staging/android/ashmem.c:361
>         call_mmap include/linux/fs.h:1830 [inline]
>         mmap_region+0xe82/0x1cd0 mm/mmap.c:1762
>         do_mmap+0xa10/0x1220 mm/mmap.c:1535
>         do_mmap_pgoff include/linux/mm.h:2298 [inline]
>         vm_mmap_pgoff+0x213/0x2c0 mm/util.c:357
>         ksys_mmap_pgoff+0x4da/0x660 mm/mmap.c:1585
>         __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
>         __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline]
>         __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91
>         do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> -> #0 (&mm->mmap_sem){++++}:
>         lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3900
>         down_read+0x8d/0x120 kernel/locking/rwsem.c:24
>         __do_page_fault+0xb61/0xec0 arch/x86/mm/fault.c:1333
>         do_page_fault+0xed/0x7d1 arch/x86/mm/fault.c:1472
>         page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1139
>         fault_in_pages_readable include/linux/pagemap.h:601 [inline]
>         iov_iter_fault_in_readable+0x1b4/0x450 lib/iov_iter.c:421
>         generic_perform_write+0x216/0x6a0 mm/filemap.c:3144
>         __generic_file_write_iter+0x26e/0x630 mm/filemap.c:3279
>         generic_file_write_iter+0x436/0x870 mm/filemap.c:3307
>         call_write_iter include/linux/fs.h:1825 [inline]
>         do_iter_readv_writev+0x8b0/0xa80 fs/read_write.c:680
>         do_iter_write+0x185/0x5f0 fs/read_write.c:959
>         vfs_writev+0x1f1/0x360 fs/read_write.c:1004
>         do_pwritev+0x1cc/0x280 fs/read_write.c:1093
>         __do_sys_pwritev fs/read_write.c:1140 [inline]
>         __se_sys_pwritev fs/read_write.c:1135 [inline]
>         __x64_sys_pwritev+0x9a/0xf0 fs/read_write.c:1135
>         do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> other info that might help us debug this:
> 
> Chain exists of:
>    &mm->mmap_sem --> ashmem_mutex --> &sb->s_type->i_mutex_key#10
> 
>   Possible unsafe locking scenario:
> 
>         CPU0                    CPU1
>         ----                    ----
>    lock(&sb->s_type->i_mutex_key#10);
>                                 lock(ashmem_mutex);
>                                 lock(&sb->s_type->i_mutex_key#10);
>    lock(&mm->mmap_sem);
> 
>   *** DEADLOCK ***
> 
> 2 locks held by syz-executor3/21327:
>   #0: 000000003de4eab1 (sb_writers#3){.+.+}, at: file_start_write  
> include/linux/fs.h:2784 [inline]
>   #0: 000000003de4eab1 (sb_writers#3){.+.+}, at: vfs_writev+0x2bd/0x360  
> fs/read_write.c:1003
>   #1: 00000000a2c51c08 (&sb->s_type->i_mutex_key#10){+.+.}, at: inode_lock  
> include/linux/fs.h:745 [inline]
>   #1: 00000000a2c51c08 (&sb->s_type->i_mutex_key#10){+.+.}, at:  
> generic_file_write_iter+0xed/0x870 mm/filemap.c:3304
> 
> stack backtrace:
> CPU: 1 PID: 21327 Comm: syz-executor3 Not tainted 4.19.0-rc4-next-20180920+  
> #76
> 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+0x1d3/0x2c4 lib/dump_stack.c:113
>   print_circular_bug.isra.33.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:2415 [inline]
>   __lock_acquire+0x33e4/0x4ec0 kernel/locking/lockdep.c:3411
>   lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3900
>   down_read+0x8d/0x120 kernel/locking/rwsem.c:24
>   __do_page_fault+0xb61/0xec0 arch/x86/mm/fault.c:1333
>   do_page_fault+0xed/0x7d1 arch/x86/mm/fault.c:1472
>   page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1139
> RIP: 0010:fault_in_pages_readable include/linux/pagemap.h:601 [inline]
> RIP: 0010:iov_iter_fault_in_readable+0x1b4/0x450 lib/iov_iter.c:421
> Code: fd 49 39 dc 76 17 eb 3c e8 e9 a0 ef fd 49 81 c4 00 10 00 00 4c 39 a5  
> 28 ff ff ff 72 2e e8 d4 a0 ef fd 0f 1f 00 0f ae e8 31 db <41> 8a 04 24 0f  
> 1f 00 31 ff 89 de 88 85 58 ff ff ff e8 c6 a1 ef fd
> RSP: 0018:ffff88018dfe7650 EFLAGS: 00010246
> RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc90005662000
> RDX: 00000000000001c2 RSI: ffffffff838daf1c RDI: 0000000000000005
> RBP: ffff88018dfe7728 R08: ffff880198ad2240 R09: ffffed00319dc039
> R10: ffffed00319dc039 R11: ffff88018cee01cb R12: 0000000020012000
> R13: 0000000000000001 R14: 0000000000000001 R15: ffff88018dfe7c50
>   generic_perform_write+0x216/0x6a0 mm/filemap.c:3144
>   __generic_file_write_iter+0x26e/0x630 mm/filemap.c:3279
>   generic_file_write_iter+0x436/0x870 mm/filemap.c:3307
>   call_write_iter include/linux/fs.h:1825 [inline]
>   do_iter_readv_writev+0x8b0/0xa80 fs/read_write.c:680
>   do_iter_write+0x185/0x5f0 fs/read_write.c:959
>   vfs_writev+0x1f1/0x360 fs/read_write.c:1004
>   do_pwritev+0x1cc/0x280 fs/read_write.c:1093
>   __do_sys_pwritev fs/read_write.c:1140 [inline]
>   __se_sys_pwritev fs/read_write.c:1135 [inline]
>   __x64_sys_pwritev+0x9a/0xf0 fs/read_write.c:1135
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457679
> Code: 1d b4 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 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f96ef162c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
> RAX: ffffffffffffffda RBX: 00007f96ef1636d4 RCX: 0000000000457679
> RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000004
> RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00000000004d4a88 R14: 00000000004c31d4 R15: 0000000000000000
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> FAULT_FLAG_ALLOW_RETRY missing 30
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> CPU: 1 PID: 21327 Comm: syz-executor3 Not tainted 4.19.0-rc4-next-20180920+  
> #76
> 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+0x1d3/0x2c4 lib/dump_stack.c:113
>   handle_userfault.cold.33+0x47/0x62 fs/userfaultfd.c:432
>   do_anonymous_page mm/memory.c:2915 [inline]
>   handle_pte_fault mm/memory.c:3732 [inline]
>   __handle_mm_fault+0x45ed/0x53e0 mm/memory.c:3858
>   handle_mm_fault+0x54f/0xc70 mm/memory.c:3895
>   __do_page_fault+0x673/0xec0 arch/x86/mm/fault.c:1397
>   do_page_fault+0xed/0x7d1 arch/x86/mm/fault.c:1472
>   page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1139
> RIP: 0010:fault_in_pages_readable include/linux/pagemap.h:601 [inline]
> RIP: 0010:iov_iter_fault_in_readable+0x1b4/0x450 lib/iov_iter.c:421
> Code: fd 49 39 dc 76 17 eb 3c e8 e9 a0 ef fd 49 81 c4 00 10 00 00 4c 39 a5  
> 28 ff ff ff 72 2e e8 d4 a0 ef fd 0f 1f 00 0f ae e8 31 db <41> 8a 04 24 0f  
> 1f 00 31 ff 89 de 88 85 58 ff ff ff e8 c6 a1 ef fd
> RSP: 0018:ffff88018dfe7650 EFLAGS: 00010246
> RAX: 0000000000040000 RBX: 0000000000000000 RCX: ffffc90005662000
> RDX: 00000000000001c2 RSI: ffffffff838daf1c RDI: 0000000000000005
> RBP: ffff88018dfe7728 R08: ffff880198ad2240 R09: ffffed00319dc039
> R10: ffffed00319dc039 R11: ffff88018cee01cb R12: 0000000020012000
> R13: 0000000000000001 R14: 0000000000000001 R15: ffff88018dfe7c50
>   generic_perform_write+0x216/0x6a0 mm/filemap.c:3144
>   __generic_file_write_iter+0x26e/0x630 mm/filemap.c:3279
>   generic_file_write_iter+0x436/0x870 mm/filemap.c:3307
>   call_write_iter include/linux/fs.h:1825 [inline]
>   do_iter_readv_writev+0x8b0/0xa80 fs/read_write.c:680
>   do_iter_write+0x185/0x5f0 fs/read_write.c:959
>   vfs_writev+0x1f1/0x360 fs/read_write.c:1004
>   do_pwritev+0x1cc/0x280 fs/read_write.c:1093
>   __do_sys_pwritev fs/read_write.c:1140 [inline]
>   __se_sys_pwritev fs/read_write.c:1135 [inline]
>   __x64_sys_pwritev+0x9a/0xf0 fs/read_write.c:1135
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457679
> Code: 1d b4 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 eb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f96ef162c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
> RAX: ffffffffffffffda RBX: 00007f96ef1636d4 RCX: 0000000000457679
> RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000004
> RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: 00000000004d4a88 R14: 00000000004c31d4 R15: 0000000000000000
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> audit: type=1326 audit(2000000012.020:46): auid=4294967295 uid=0 gid=0  
> ses=4294967295 subj==unconfined pid=21534 comm="syz-executor0"  
> exe="/root/syz-executor0" sig=31 arch=c000003e syscall=202 compat=0  
> ip=0x457679 code=0x0
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> audit: type=1326 audit(2000000012.950:47): auid=4294967295 uid=0 gid=0  
> ses=4294967295 subj==unconfined pid=21566 comm="syz-executor0"  
> exe="/root/syz-executor0" sig=31 arch=c000003e syscall=202 compat=0  
> ip=0x457679 code=0x0
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop2' (00000000dc629c38): kobject_uevent_env
> kobject: 'loop2' (00000000dc629c38): fill_kobj_path: path  
> = '/devices/virtual/block/loop2'
> kobject: 'loop3' (00000000aff594d4): kobject_uevent_env
> kobject: 'loop3' (00000000aff594d4): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> kobject: 'loop4' (000000004119f3b1): kobject_uevent_env
> kobject: 'loop4' (000000004119f3b1): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> audit: type=1326 audit(2000000013.460:48): auid=4294967295 uid=0 gid=0  
> ses=4294967295 subj==unconfined pid=21585 comm="syz-executor4"  
> exe="/root/syz-executor4" sig=31 arch=c000003e syscall=202 compat=0  
> ip=0x457679 code=0x0
> audit: type=1326 audit(2000000013.510:49): auid=4294967295 uid=0 gid=0  
> ses=4294967295 subj==unconfined pid=21588 comm="syz-executor2"  
> exe="/root/syz-executor2" sig=31 arch=c000003e syscall=202 compat=0  
> ip=0x457679 code=0x0
> kobject: 'loop1' (00000000980d23a1): kobject_uevent_env
> kobject: 'loop1' (00000000980d23a1): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> kobject: 'loop0' (00000000ee0adfaf): kobject_uevent_env
> kobject: 'loop0' (00000000ee0adfaf): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> audit: type=1326 audit(2000000013.800:50): auid=4294967295 uid=0 gid=0  
> ses=4294967295 subj==unconfined pid=21601 comm="syz-executor0"  
> exe="/root/syz-executor0" sig=31 arch=c000003e syscall=202 compat=0  
> ip=0x457679 code=0x0
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> kobject: 'loop5' (00000000699d1086): kobject_uevent_env
> kobject: 'loop5' (00000000699d1086): fill_kobj_path: path  
> = '/devices/virtual/block/loop5'
> 
> 
> ---
> 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.