==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801d0559668 by task blkid/2481

CPU: 1 PID: 2481 Comm: blkid Not tainted 4.4.174+ #17
 0000000000000000 da71270ffea5636d ffff8800b3697730 ffffffff81aad1a1
 0000000000000000 ffffea0007415600 ffff8801d0559668 0000000000000008
 0000000000000000 ffff8800b3697768 ffffffff81490120 0000000000000000
Call Trace:
 [<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81490120>] print_address_description+0x6f/0x21b mm/kasan/report.c:252
 [<ffffffff81490358>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff81490358>] kasan_report mm/kasan/report.c:408 [inline]
 [<ffffffff81490358>] kasan_report.cold+0x8c/0x2be mm/kasan/report.c:393
 [<ffffffff81484ed4>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81a82965>] disk_unblock_events+0x55/0x60 block/genhd.c:1543
 [<ffffffff8154efcc>] __blkdev_get+0x70c/0xdf0 fs/block_dev.c:1297
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff8149599d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149599d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Allocated by task 2465:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81483f22>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81483f22>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81483f22>] kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:616
 [<ffffffff81484197>] kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
 [<ffffffff814801a3>] kmem_cache_alloc_trace+0x123/0x2d0 mm/slub.c:2642
 [<ffffffff81a81b50>] kmem_cache_alloc_node_trace include/linux/slab.h:367 [inline]
 [<ffffffff81a81b50>] kmalloc_node include/linux/slab.h:514 [inline]
 [<ffffffff81a81b50>] kzalloc_node include/linux/slab.h:631 [inline]
 [<ffffffff81a81b50>] alloc_disk_node+0x50/0x3c0 block/genhd.c:1282
 [<ffffffff81a81edb>] alloc_disk+0x1b/0x20 block/genhd.c:1274
 [<ffffffff81d436d0>] loop_add+0x380/0x830 drivers/block/loop.c:1857
 [<ffffffff81d440a8>] loop_control_ioctl+0x138/0x2f0 drivers/block/loop.c:1988
 [<ffffffff8159b2c3>] C_SYSC_ioctl fs/compat_ioctl.c:1592 [inline]
 [<ffffffff8159b2c3>] compat_SyS_ioctl+0x403/0x2210 fs/compat_ioctl.c:1544
 [<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
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

Freed by task 2481:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff81484820>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff81484820>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff81484820>] kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:589
 [<ffffffff81481c44>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff81481c44>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff81481c44>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff81481c44>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff81a80375>] disk_release+0x255/0x330 block/genhd.c:1118
 [<ffffffff81cf785d>] device_release+0x7d/0x220 drivers/base/core.c:247
 [<ffffffff81ab309c>] kobject_cleanup lib/kobject.c:643 [inline]
 [<ffffffff81ab309c>] kobject_release lib/kobject.c:672 [inline]
 [<ffffffff81ab309c>] kref_sub include/linux/kref.h:73 [inline]
 [<ffffffff81ab309c>] kref_put include/linux/kref.h:98 [inline]
 [<ffffffff81ab309c>] kobject_put+0x14c/0x260 lib/kobject.c:689
 [<ffffffff81a7e013>] put_disk+0x23/0x30 block/genhd.c:1346
 [<ffffffff8154ef2c>] __blkdev_get+0x66c/0xdf0 fs/block_dev.c:1290
 [<ffffffff81551938>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353
 [<ffffffff8155219a>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508
 [<ffffffff8149154f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
 [<ffffffff81494d3b>] vfs_open+0x10b/0x210 fs/open.c:862
 [<ffffffff814c5ddf>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814c5ddf>] path_openat+0x136f/0x4470 fs/namei.c:3406
 [<ffffffff814ccab1>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
 [<ffffffff81495668>] do_sys_open+0x2f8/0x600 fs/open.c:1038
 [<ffffffff8149599d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149599d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

The buggy address belongs to the object at ffff8801d0559100
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d0559100, ffff8801d0559900)
The buggy address belongs to the page:
vma ffffea00074155e0 start ffffea0007415401 end ffffea00074155e0
next           (null) prev           (null) mm dead000000000100
prot dead000000000200 anon_vma 0000000300000001 vm_ops           (null)
pgoff 0 file 4000000000000000 private_data           (null)
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory accessBUG: unable to handle kernel paging request at fffff24000e82b18
IP: [<ffffffff81439ffd>] handle_pte_fault mm/memory.c:3338 [inline]
IP: [<ffffffff81439ffd>] __handle_mm_fault mm/memory.c:3474 [inline]
IP: [<ffffffff81439ffd>] handle_mm_fault+0x32d/0x3140 mm/memory.c:3503
PGD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 1921 Comm: rsyslogd Not tainted 4.4.174+ #17
task: ffff8800b8cd2f80 task.stack: ffff8801d6bd8000
RIP: 0010:[<ffffffff81439ffd>]  [<ffffffff81439ffd>] handle_pte_fault mm/memory.c:3338 [inline]
RIP: 0010:[<ffffffff81439ffd>]  [<ffffffff81439ffd>] __handle_mm_fault mm/memory.c:3474 [inline]
RIP: 0010:[<ffffffff81439ffd>]  [<ffffffff81439ffd>] handle_mm_fault+0x32d/0x3140 mm/memory.c:3503
RSP: 0018:ffff8801d6bdf8d0  EFLAGS: 00010a06
RAX: dffffc0000000000 RBX: ffff8801d6bdfa18 RCX: ffff880000000000
RDX: 1ffff64000e82b18 RSI: ffffffff81439fd1 RDI: ffffea0007415600
RBP: ffff8801d6bdfa40 R08: 0000000000000001 R09: ffff8800b8cd3890
R10: ffffffff82836880 R11: 0000000000000000 R12: ffffb200074158c0
R13: 00003ffffffff000 R14: ffff880000000000 R15: 00000000000008c0
FS:  00007efc24ce4700(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff24000e82b18 CR3: 00000000b779f000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 000000400000000b ffff8801d6bdf8e8 ffff8801d6bdf9e8 0000000000000002
 ffff8801d1864910 ffff8801d6bdf920 ffffffff814842f6 ffff8801d1864910
 ffffffff8285554d 0000000000000226 ffff8800000008c0 1ffff1003ad7bf2b
Call Trace:
 [<ffffffff810aaa4e>] __do_page_fault+0x28e/0x7f0 arch/x86/mm/fault.c:1243
 [<ffffffff810ab008>] do_page_fault+0x28/0x30 arch/x86/mm/fault.c:1306
 [<ffffffff82719e35>] page_fault+0x25/0x30 arch/x86/entry/entry_64.S:1064
 [<ffffffff81608274>] kmsg_read+0x74/0xa0 fs/proc/kmsg.c:39
 [<ffffffff815e03bd>] proc_reg_read+0xfd/0x180 fs/proc/inode.c:202
 [<ffffffff81496556>] __vfs_read+0x116/0x3c0 fs/read_write.c:434
 [<ffffffff81498264>] vfs_read+0x134/0x360 fs/read_write.c:456
 [<ffffffff8149aa8c>] SYSC_read fs/read_write.c:571 [inline]
 [<ffffffff8149aa8c>] SyS_read+0xdc/0x1c0 fs/read_write.c:564
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: b9 00 00 00 00 00 88 ff ff 49 8d 04 0f 4d 21 ec 49 01 c4 48 89 85 e0 fe ff ff 48 b8 00 00 00 00 00 fc ff df 4c 89 e2 48 c1 ea 03 <80> 3c 02 00 0f 85 09 28 00 00 4d 8b 34 24 49 bd ff 0f 00 00 00 
RIP  [<ffffffff81439ffd>] handle_pte_fault mm/memory.c:3338 [inline]
RIP  [<ffffffff81439ffd>] __handle_mm_fault mm/memory.c:3474 [inline]
RIP  [<ffffffff81439ffd>] handle_mm_fault+0x32d/0x3140 mm/memory.c:3503
 RSP <ffff8801d6bdf8d0>
CR2: fffff24000e82b18
---[ end trace e9e1cf6f049bd8ac ]---