==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8800bb48f3e8 by task blkid/2682

CPU: 0 PID: 2682 Comm: blkid Not tainted 4.4.172+ #13
 0000000000000000 332adde1b6e14b29 ffff8800bb4cf730 ffffffff81aacde1
 0000000000000000 ffffea0002ed2200 ffff8800bb48f3e8 0000000000000008
 0000000000000000 ffff8800bb4cf768 ffffffff8148fedd 0000000000000000
Call Trace:
 [<ffffffff81aacde1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aacde1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff8148fedd>] print_address_description+0x6f/0x21b mm/kasan/report.c:252
 [<ffffffff81490115>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81490115>] kasan_report mm/kasan/report.c:408 [inline]
 [<ffffffff81490115>] kasan_report.cold+0x8c/0x2be mm/kasan/report.c:393
 [<ffffffff81484cc4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81a825a5>] disk_unblock_events+0x55/0x60 block/genhd.c:1543
 [<ffffffff8154ec0c>] __blkdev_get+0x70c/0xdf0 fs/block_dev.c:1297
 [<ffffffff81551578>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff81551dda>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149130f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494afb>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5a1f>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5a1f>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814cc6f1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495428>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff8149575d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149575d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82718621>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Allocated by task 2674:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81483d12>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81483d12>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81483d12>] kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:616
 [<ffffffff81483f87>] kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
 [<ffffffff8147ff93>] kmem_cache_alloc_trace+0x123/0x2d0 mm/slub.c:2642
 [<ffffffff81a81790>] kmem_cache_alloc_node_trace include/linux/slab.h:367 [inline]
 [<ffffffff81a81790>] kmalloc_node include/linux/slab.h:514 [inline]
 [<ffffffff81a81790>] kzalloc_node include/linux/slab.h:631 [inline]
 [<ffffffff81a81790>] alloc_disk_node+0x50/0x3c0 block/genhd.c:1282
 [<ffffffff81a81b1b>] alloc_disk+0x1b/0x20 block/genhd.c:1274
 [<ffffffff81d43130>] loop_add+0x380/0x830 drivers/block/loop.c:1854
 [<ffffffff81d43bc2>] loop_control_ioctl drivers/block/loop.c:1989 [inline]
 [<ffffffff81d43bc2>] loop_control_ioctl+0x132/0x2f0 drivers/block/loop.c:1971
 [<ffffffff814d2037>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff814d2037>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff814d2037>] do_vfs_ioctl+0x6e7/0xfa0 fs/ioctl.c:605
 [<ffffffff814d297f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff814d297f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff82718621>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Freed by task 2682:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81484610>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81484610>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81484610>] kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:589
 [<ffffffff81481a34>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff81481a34>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff81481a34>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff81481a34>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff81a7ffb5>] disk_release+0x255/0x330 block/genhd.c:1118
 [<ffffffff81cf745d>] device_release+0x7d/0x220 drivers/base/core.c:247
 [<ffffffff81ab2cdc>] kobject_cleanup lib/kobject.c:643 [inline]
 [<ffffffff81ab2cdc>] kobject_release lib/kobject.c:672 [inline]
 [<ffffffff81ab2cdc>] kref_sub include/linux/kref.h:73 [inline]
 [<ffffffff81ab2cdc>] kref_put include/linux/kref.h:98 [inline]
 [<ffffffff81ab2cdc>] kobject_put+0x14c/0x260 lib/kobject.c:689
 [<ffffffff81a7dc53>] put_disk+0x23/0x30 block/genhd.c:1346
 [<ffffffff8154eb6c>] __blkdev_get+0x66c/0xdf0 fs/block_dev.c:1290
 [<ffffffff81551578>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff81551dda>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149130f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494afb>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5a1f>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5a1f>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814cc6f1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495428>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff8149575d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149575d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82718621>] entry_SYSCALL_64_fastpath+0x1e/0x9a

The buggy address belongs to the object at ffff8800bb48ee80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8800bb48ee80, ffff8800bb48f680)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at fffffbfffc053b4b
IP: [<ffffffff8123ae1d>] rcu_sync_lockdep_assert+0x5d/0xb0 kernel/rcu/sync.c:68
PGD 21ff68067 PUD 21ff67067 PMD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 2955 Comm: syz-executor553 Not tainted 4.4.172+ #13
task: ffff8801cea90000 task.stack: ffff8801cea98000
RIP: 0010:[<ffffffff8123ae1d>]  [<ffffffff8123ae1d>] rcu_sync_lockdep_assert+0x5d/0xb0 kernel/rcu/sync.c:68
RSP: 0018:ffff8801cea9fc20  EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: 0000000002ed2200 RCX: 1ffffffff05f7178
RDX: 1ffffffffc053b4b RSI: ffffffff81b0a7fc RDI: ffffffffe029da58
RBP: ffff8801cea9fc28 R08: ffff8801d4dd59a0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000148
R13: ffff8800bb496600 R14: ffff8800bb4969b8 R15: 0000000000000000
FS:  0000000002599880(0063) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffbfffc053b4b CR3: 00000001d9153000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800bb4969b8 ffff8801cea9fc68 ffffffff8149e59f 0000001d811ea67b
 ffff8801d6dcb720 ffff8801d40ce620 ffff8801d40ce670 ffff8801d42d5888
 0000000000000001 ffff8801cea9fd00 ffffffff814b0bf4 ffff8801cea90008
Call Trace:
 [<ffffffff8149e59f>] rcu_sync_is_idle include/linux/rcu_sync.h:56 [inline]
 [<ffffffff8149e59f>] percpu_down_read_trylock include/linux/percpu-rwsem.h:56 [inline]
 [<ffffffff8149e59f>] __sb_start_write+0xdf/0x310 fs/super.c:1223
 [<ffffffff814b0bf4>] sb_start_write_trylock include/linux/fs.h:1522 [inline]
 [<ffffffff814b0bf4>] pipe_write+0x8f4/0xe70 fs/pipe.c:472
 [<ffffffff81496788>] new_sync_write fs/read_write.c:478 [inline]
 [<ffffffff81496788>] __vfs_write+0x2e8/0x3d0 fs/read_write.c:491
 [<ffffffff814982b2>] vfs_write+0x182/0x4e0 fs/read_write.c:538
 [<ffffffff8149a8ec>] SYSC_write fs/read_write.c:585 [inline]
 [<ffffffff8149a8ec>] SyS_write+0xdc/0x1c0 fs/read_write.c:577
 [<ffffffff82718621>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: 02 84 c0 74 04 3c 03 7e 60 48 b8 00 00 00 00 00 fc ff df 8b 5b 68 48 89 df 48 c1 e7 05 48 81 c7 58 9a 85 82 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 3f 48 c1 e3 05 48 8b 83 58 9a 85 82 e8 3d 2a 4e 
RIP  [<ffffffff8123ae1d>] rcu_sync_lockdep_assert+0x5d/0xb0 kernel/rcu/sync.c:68
 RSP <ffff8801cea9fc20>
CR2: fffffbfffc053b4b
---[ end trace a9f5402e5043da3b ]---