==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801d2059ee8 by task blkid/3233

CPU: 1 PID: 3233 Comm: blkid Not tainted 4.4.172+ #13
 0000000000000000 b4f95ede9c3003c2 ffff8801d1a8f730 ffffffff81aacde1
 0000000000000000 ffffea0007481600 ffff8801d2059ee8 0000000000000008
 0000000000000000 ffff8801d1a8f768 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 3213:
 [<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
 [<ffffffff81d439a4>] loop_probe+0x154/0x180 drivers/block/loop.c:1960
 [<ffffffff81d0eac1>] kobj_lookup+0x221/0x410 drivers/base/map.c:124
 [<ffffffff81a7fa7c>] get_gendisk+0x3c/0x2e0 block/genhd.c:689
 [<ffffffff8154e89c>] __blkdev_get+0x39c/0xdf0 fs/block_dev.c:1193
 [<ffffffff81551711>] blkdev_get+0x481/0x920 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
 [<ffffffff8159988a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff8159988a>] compat_SyS_open+0x2a/0x40 fs/compat.c:1090
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff82719dd0>] sysenter_flags_fixed+0xd/0x1a

Freed by task 3233:
 [<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 ffff8801d2059980
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d2059980, ffff8801d205a180)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at ffffed043a3476e7
IP: [<ffffffff8112cf71>] ns_of_pid include/linux/pid.h:140 [inline]
IP: [<ffffffff8112cf71>] task_active_pid_ns kernel/pid.c:546 [inline]
IP: [<ffffffff8112cf71>] __task_pid_nr_ns+0x361/0x450 kernel/pid.c:529
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: [<          (null)>]           (null)
------------[ cut here ]------------
WARNING: CPU: 0 PID: -2104943648 at include/linux/uaccess.h:18 pagefault_disabled_dec include/linux/uaccess.h:18 [inline]()
WARNING: CPU: 0 PID: -2104943648 at include/linux/uaccess.h:18 pagefault_enable include/linux/uaccess.h:45 [inline]()
WARNING: CPU: 0 PID: -2104943648 at include/linux/uaccess.h:18 __probe_kernel_read+0x1ee/0x230 mm/maccess.c:35()