==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x51/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801d8bb40e8 by task blkid/2856

CPU: 0 PID: 2856 Comm: blkid Not tainted 4.4.162+ #7
 0000000000000000 4ee4f871fea24ecd ffff8801d749f6d0 ffffffff81a994bd
 ffffea000762ec00 ffff8801d8bb40e8 0000000000000000 ffff8801d8bb40e8
 0000000000000000 ffff8801d749f708 ffffffff8148a669 ffff8801d8bb40e8
Call Trace:
 [<ffffffff81a994bd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81a994bd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8148a669>] print_address_description+0x6c/0x217 mm/kasan/report.c:252
 [<ffffffff8148a989>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8148a989>] kasan_report.cold.6+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff8147f604>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81a6eb31>] disk_unblock_events+0x51/0x60 block/genhd.c:1543
 [<ffffffff8154805c>] __blkdev_get+0x70c/0xdf0 fs/block_dev.c:1297
 [<ffffffff8154a9ca>] blkdev_get+0x2da/0x920 fs/block_dev.c:1353
 [<ffffffff8154b225>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1508
 [<ffffffff8148ba0d>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
 [<ffffffff8148f17a>] vfs_open+0x12a/0x210 fs/open.c:862
 [<ffffffff814bed5c>] do_last fs/namei.c:3222 [inline]
 [<ffffffff814bed5c>] path_openat+0x50c/0x39a0 fs/namei.c:3359
 [<ffffffff814c5e87>] do_filp_open+0x197/0x270 fs/namei.c:3393
 [<ffffffff8148fa9c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff8148fdbd>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8148fdbd>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff827062e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Allocated by task 2834:
 [<ffffffff8102e496>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff8147e642>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff8147e642>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff8147e642>] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:616
 [<ffffffff8147e8bf>] kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:601
 [<ffffffff8147a887>] kmem_cache_alloc_trace+0x117/0x2d0 mm/slub.c:2642
 [<ffffffff81a6dd54>] kmem_cache_alloc_node_trace include/linux/slab.h:367 [inline]
 [<ffffffff81a6dd54>] kmalloc_node include/linux/slab.h:514 [inline]
 [<ffffffff81a6dd54>] kzalloc_node include/linux/slab.h:631 [inline]
 [<ffffffff81a6dd54>] alloc_disk_node+0x54/0x3a0 block/genhd.c:1282
 [<ffffffff81a6e0b8>] alloc_disk+0x18/0x20 block/genhd.c:1274
 [<ffffffff81d2faab>] loop_add+0x36b/0x7c0 drivers/block/loop.c:1824
 [<ffffffff81d302cf>] loop_probe+0x14f/0x180 drivers/block/loop.c:1931
 [<ffffffff81cfbc93>] kobj_lookup+0x223/0x410 drivers/base/map.c:124
 [<ffffffff81a6c0a9>] get_gendisk+0x39/0x2d0 block/genhd.c:689
 [<ffffffff81547cec>] __blkdev_get+0x39c/0xdf0 fs/block_dev.c:1193
 [<ffffffff8154ab78>] blkdev_get+0x488/0x920 fs/block_dev.c:1353
 [<ffffffff8154b225>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1508
 [<ffffffff8148ba0d>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
 [<ffffffff8148f17a>] vfs_open+0x12a/0x210 fs/open.c:862
 [<ffffffff814bed5c>] do_last fs/namei.c:3222 [inline]
 [<ffffffff814bed5c>] path_openat+0x50c/0x39a0 fs/namei.c:3359
 [<ffffffff814c5e87>] do_filp_open+0x197/0x270 fs/namei.c:3393
 [<ffffffff8148fa9c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff81591dda>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81591dda>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
 [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a

Freed by task 2856:
 [<ffffffff8102e496>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff8147ef3c>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff8147ef3c>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff8147ef3c>] kasan_slab_free+0xac/0x190 mm/kasan/kasan.c:589
 [<ffffffff8147c314>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff8147c314>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff8147c314>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff8147c314>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff81a6c5d9>] disk_release+0x259/0x330 block/genhd.c:1118
 [<ffffffff81ce44de>] device_release+0x7e/0x220 drivers/base/core.c:247
 [<ffffffff81a9f2b4>] kobject_cleanup lib/kobject.c:643 [inline]
 [<ffffffff81a9f2b4>] kobject_release lib/kobject.c:672 [inline]
 [<ffffffff81a9f2b4>] kref_sub include/linux/kref.h:73 [inline]
 [<ffffffff81a9f2b4>] kref_put include/linux/kref.h:98 [inline]
 [<ffffffff81a9f2b4>] kobject_put+0x144/0x260 lib/kobject.c:689
 [<ffffffff81a6a2e3>] put_disk+0x23/0x30 block/genhd.c:1346
 [<ffffffff81547fbc>] __blkdev_get+0x66c/0xdf0 fs/block_dev.c:1290
 [<ffffffff8154a9ca>] blkdev_get+0x2da/0x920 fs/block_dev.c:1353
 [<ffffffff8154b225>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1508
 [<ffffffff8148ba0d>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
 [<ffffffff8148f17a>] vfs_open+0x12a/0x210 fs/open.c:862
 [<ffffffff814bed5c>] do_last fs/namei.c:3222 [inline]
 [<ffffffff814bed5c>] path_openat+0x50c/0x39a0 fs/namei.c:3359
 [<ffffffff814c5e87>] do_filp_open+0x197/0x270 fs/namei.c:3393
 [<ffffffff8148fa9c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff8148fdbd>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8148fdbd>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff827062e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

The buggy address belongs to the object at ffff8801d8bb3b80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d8bb3b80, ffff8801d8bb4380)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 3312 Comm: syz-executor516 Not tainted 4.4.162+ #7
task: ffff8800b1b3df00 task.stack: ffff8800b1b68000
RIP: 0010:[<ffffffff81af9021>]  [<ffffffff81af9021>] lookup_object lib/debugobjects.c:120 [inline]
RIP: 0010:[<ffffffff81af9021>]  [<ffffffff81af9021>] debug_object_deactivate+0x191/0x340 lib/debugobjects.c:468
RSP: 0018:ffff8801db707ce0  EFLAGS: 00010002
RAX: dffffc0000000000 RBX: 4000000000004080 RCX: 0800000000000813
RDX: 1ffffffff080e713 RSI: ffffffff82eafea0 RDI: 4000000000004098
RBP: ffff8801db707da0 R08: ffff8800b1b3e810 R09: 000000000010a002
R10: ffff8800b1b3df00 R11: 0000000000000001 R12: 1ffff1003b6e0f9e
R13: ffffffff84073888 R14: ffff8800b6487d28 R15: 0000000000000003
FS:  0000000000000000(0000) GS:ffff8801db700000(0063) knlGS:000000000958e840
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00000000080bfdda CR3: 00000000b906d000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000000000096 ffffffff82eafea0 0000000041b58ab3 ffffffff82c5f17d
 ffffffff81af8e90 0000000000000046 0000000000000000 ffffffff8125ccbd
 ffff880000000000 0000000000000000 dffffc0000000000 ffff8800b1b3e7c0
Call Trace:
 <IRQ> 
 [<ffffffff8125cae5>] debug_hrtimer_deactivate kernel/time/hrtimer.c:415 [inline]
 [<ffffffff8125cae5>] debug_deactivate kernel/time/hrtimer.c:462 [inline]
 [<ffffffff8125cae5>] __run_hrtimer kernel/time/hrtimer.c:1230 [inline]
 [<ffffffff8125cae5>] __hrtimer_run_queues+0x215/0xfc0 kernel/time/hrtimer.c:1325
 [<ffffffff8125f8e1>] hrtimer_interrupt+0x1b1/0x430 kernel/time/hrtimer.c:1359
 [<ffffffff8108b4c4>] local_apic_timer_interrupt+0x74/0xa0 arch/x86/kernel/apic/apic.c:901
 [<ffffffff8270893c>] smp_apic_timer_interrupt+0x7c/0xa0 arch/x86/kernel/apic/apic.c:925
 [<ffffffff82707c9d>] apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:741
 <EOI> 
 [<ffffffff811e510b>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff811e510b>] __wake_up_sync_key+0x4b/0x60 kernel/sched/wait.c:146
 [<ffffffff814ab1c8>] pipe_write+0x8e8/0xd80 fs/pipe.c:469
 [<ffffffff81490e04>] new_sync_write fs/read_write.c:478 [inline]
 [<ffffffff81490e04>] __vfs_write+0x304/0x3e0 fs/read_write.c:491
 [<ffffffff814928ce>] vfs_write+0x17e/0x4e0 fs/read_write.c:538
 [<ffffffff81494f09>] SYSC_write fs/read_write.c:585 [inline]
 [<ffffffff81494f09>] SyS_write+0xd9/0x1c0 fs/read_write.c:577
 [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
 [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a
Code: a9 01 00 00 48 8b 1b 41 bf 01 00 00 00 48 85 db 74 42 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 18 41 83 c7 01 48 89 f9 48 c1 e9 03 <80> 3c 01 00 0f 85 0c 01 00 00 4c 3b 73 18 74 7d 48 89 d9 48 c1 
RIP  [<ffffffff81af9021>] lookup_object lib/debugobjects.c:120 [inline]
RIP  [<ffffffff81af9021>] debug_object_deactivate+0x191/0x340 lib/debugobjects.c:468
 RSP <ffff8801db707ce0>
---[ end trace e932fce4da9a1a5c ]---