==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x51/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801d2642fe8 by task blkid/2578

CPU: 0 PID: 2578 Comm: blkid Not tainted 4.4.162+ #7
 0000000000000000 1e730fc92ccaf3a8 ffff8800b5b3f6d0 ffffffff81a994bd
 ffffea0007499000 ffff8801d2642fe8 0000000000000000 ffff8801d2642fe8
 0000000000000000 ffff8800b5b3f708 ffffffff8148a669 ffff8801d2642fe8
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 2569:
 [<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
 [<ffffffff8154a7e6>] bd_start_claiming fs/block_dev.c:851 [inline]
 [<ffffffff8154a7e6>] blkdev_get+0xf6/0x920 fs/block_dev.c:1346
 [<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 2578:
 [<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 ffff8801d2642a80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d2642a80, ffff8801d2643280)
The buggy address belongs to the page:
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: -2104946016 Comm: €*dÒ
ˆÿÿ€2dÒ
ˆÿÿÐ6µ Not tainted 4.4.162+ #7
task: ffff8800b5112f80 task.stack: ffff8801d2643280
RIP: 0010:[<ffffffff8117d18d>]  [<ffffffff8117d18d>] entity_before kernel/sched/fair.c:512 [inline]
RIP: 0010:[<ffffffff8117d18d>]  [<ffffffff8117d18d>] __enqueue_entity+0x7d/0x230 kernel/sched/fair.c:561
RSP: 0018:ffff8801db707b20  EFLAGS: 00010007
RAX: 0cc000000000108b RBX: 660000000000841f RCX: ffff8801db71e928
RDX: 0000000000000000 RSI: ffff8801db71e950 RDI: 660000000000845f
RBP: ffff8801db707b70 R08: ffff8801d40700b0 R09: ffffffff81425f4f
R10: ffffffff831a2338 R11: ffffffff82835e80 R12: 00000002698fac23
R13: dffffc0000000000 R14: ffff8801d4070060 R15: ffffed003a80e016
FS:  00007f8b166b97a0(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000ffb01a28 CR3: 00000000b8372000 CR4: 00000000001606b0
Stack:
 ffff8801db707b60 ffffffff81af752b ffff8801db707b70 ffffffff8117cc3f
 ffff8801db71e880 ffff8801d4070060 ffff8800b5112fe0 ffff8801db71e928
 dffffc0000000000 0000000269e4a83e ffff8801db707c90 ffffffff8119d208
Call Trace:
 <IRQ> 
 [<ffffffff8119d208>] enqueue_entity kernel/sched/fair.c:3526 [inline]
 [<ffffffff8119d208>] enqueue_task_fair+0x14c8/0xab90 kernel/sched/fair.c:4695
 [<ffffffff8116384d>] enqueue_task kernel/sched/core.c:858 [inline]
 [<ffffffff8116384d>] activate_task+0x1dd/0x280 kernel/sched/core.c:874
 [<ffffffff81164a2f>] ttwu_activate kernel/sched/core.c:1736 [inline]
 [<ffffffff81164a2f>] ttwu_do_activate.constprop.29+0xbf/0x1e0 kernel/sched/core.c:1789
 [<ffffffff81167ecd>] ttwu_queue kernel/sched/core.c:1934 [inline]
 [<ffffffff81167ecd>] try_to_wake_up+0x6dd/0x1120 kernel/sched/core.c:2068
 [<ffffffff81168a55>] wake_up_process+0x15/0x20 kernel/sched/core.c:2142
 [<ffffffff8125bbe8>] hrtimer_wakeup+0x48/0x60 kernel/time/hrtimer.c:1482
 [<ffffffff8125cc60>] __run_hrtimer kernel/time/hrtimer.c:1261 [inline]
 [<ffffffff8125cc60>] __hrtimer_run_queues+0x390/0xfc0 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> 
Code: 
------------[ cut here ]------------
WARNING: CPU: 1 PID: -2104946016 at include/linux/uaccess.h:15 pagefault_disabled_dec include/linux/uaccess.h:15 [inline]()
WARNING: CPU: 1 PID: -2104946016 at include/linux/uaccess.h:15 pagefault_enable include/linux/uaccess.h:42 [inline]()
WARNING: CPU: 1 PID: -2104946016 at include/linux/uaccess.h:15 __probe_kernel_read+0x1e3/0x230 mm/maccess.c:35()