==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x51/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801d2157c68 by task blkid/2260

CPU: 0 PID: 2260 Comm: blkid Not tainted 4.4.166+ #4
 0000000000000000 d7fc45356407938e ffff8801d1caf6d0 ffffffff81aa62ad
 ffffea0007485400 ffff8801d2157c68 0000000000000000 ffff8801d2157c68
 0000000000000000 ffff8801d1caf708 ffffffff8148b12b ffff8801d2157c68
Call Trace:
 [<ffffffff81aa62ad>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aa62ad>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8148b12b>] print_address_description+0x6c/0x217 mm/kasan/report.c:252
 [<ffffffff8148b44b>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8148b44b>] kasan_report.cold.6+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff81480174>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:429
 [<ffffffff81a7b921>] disk_unblock_events+0x51/0x60 block/genhd.c:1543
 [<ffffffff8154911c>] __blkdev_get+0x70c/0xdf0 fs/block_dev.c:1297
 [<ffffffff8154ba8a>] blkdev_get+0x2da/0x920 fs/block_dev.c:1353
 [<ffffffff8154c2e5>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1508
 [<ffffffff8148c4cd>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
 [<ffffffff8148fc3a>] vfs_open+0x12a/0x210 fs/open.c:862
 [<ffffffff814bff20>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814bff20>] path_openat+0xc10/0x3f10 fs/namei.c:3406
 [<ffffffff814c6eb7>] do_filp_open+0x197/0x270 fs/namei.c:3440
 [<ffffffff8149055c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff8149087d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149087d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82715da1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Allocated by task 2254:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff8147f1b2>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff8147f1b2>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff8147f1b2>] kasan_kmalloc.part.1+0x62/0xf0 mm/kasan/kasan.c:616
 [<ffffffff8147f42f>] kasan_kmalloc+0xaf/0xc0 mm/kasan/kasan.c:601
 [<ffffffff8147b3e7>] kmem_cache_alloc_trace+0x117/0x2d0 mm/slub.c:2642
 [<ffffffff81a7ab44>] kmem_cache_alloc_node_trace include/linux/slab.h:367 [inline]
 [<ffffffff81a7ab44>] kmalloc_node include/linux/slab.h:514 [inline]
 [<ffffffff81a7ab44>] kzalloc_node include/linux/slab.h:631 [inline]
 [<ffffffff81a7ab44>] alloc_disk_node+0x54/0x3a0 block/genhd.c:1282
 [<ffffffff81a7aea8>] alloc_disk+0x18/0x20 block/genhd.c:1274
 [<ffffffff81d3c8db>] loop_add+0x36b/0x7c0 drivers/block/loop.c:1824
 [<ffffffff81d3d266>] loop_control_ioctl+0x136/0x300 drivers/block/loop.c:1956
 [<ffffffff814cc97f>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff814cc97f>] file_ioctl fs/ioctl.c:470 [inline]
 [<ffffffff814cc97f>] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605
 [<ffffffff814cd30f>] SYSC_ioctl fs/ioctl.c:622 [inline]
 [<ffffffff814cd30f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613
 [<ffffffff82715da1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

Freed by task 2260:
 [<ffffffff8102e3c6>] save_stack_trace+0x26/0x50 arch/x86/kernel/stacktrace.c:63
 [<ffffffff8147faac>] save_stack mm/kasan/kasan.c:512 [inline]
 [<ffffffff8147faac>] set_track mm/kasan/kasan.c:524 [inline]
 [<ffffffff8147faac>] kasan_slab_free+0xac/0x190 mm/kasan/kasan.c:589
 [<ffffffff8147ce84>] slab_free_hook mm/slub.c:1383 [inline]
 [<ffffffff8147ce84>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff8147ce84>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff8147ce84>] kfree+0xf4/0x310 mm/slub.c:3749
 [<ffffffff81a793c9>] disk_release+0x259/0x330 block/genhd.c:1118
 [<ffffffff81cf130e>] device_release+0x7e/0x220 drivers/base/core.c:247
 [<ffffffff81aac0a4>] kobject_cleanup lib/kobject.c:643 [inline]
 [<ffffffff81aac0a4>] kobject_release lib/kobject.c:672 [inline]
 [<ffffffff81aac0a4>] kref_sub include/linux/kref.h:73 [inline]
 [<ffffffff81aac0a4>] kref_put include/linux/kref.h:98 [inline]
 [<ffffffff81aac0a4>] kobject_put+0x144/0x260 lib/kobject.c:689
 [<ffffffff81a770d3>] put_disk+0x23/0x30 block/genhd.c:1346
 [<ffffffff8154907c>] __blkdev_get+0x66c/0xdf0 fs/block_dev.c:1290
 [<ffffffff8154ba8a>] blkdev_get+0x2da/0x920 fs/block_dev.c:1353
 [<ffffffff8154c2e5>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1508
 [<ffffffff8148c4cd>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
 [<ffffffff8148fc3a>] vfs_open+0x12a/0x210 fs/open.c:862
 [<ffffffff814bff20>] do_last fs/namei.c:3269 [inline]
 [<ffffffff814bff20>] path_openat+0xc10/0x3f10 fs/namei.c:3406
 [<ffffffff814c6eb7>] do_filp_open+0x197/0x270 fs/namei.c:3440
 [<ffffffff8149055c>] do_sys_open+0x31c/0x610 fs/open.c:1038
 [<ffffffff8149087d>] SYSC_open fs/open.c:1056 [inline]
 [<ffffffff8149087d>] SyS_open+0x2d/0x40 fs/open.c:1051
 [<ffffffff82715da1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

The buggy address belongs to the object at ffff8801d2157700
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d2157700, ffff8801d2157f00)
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: 2521 Comm: syz-executor694 Not tainted 4.4.166+ #4
task: ffff8800b22717c0 task.stack: ffff8800b2288000
RIP: 0010:[<ffffffff81b06f62>]  [<ffffffff81b06f62>] __debug_check_no_obj_freed lib/debugobjects.c:692 [inline]
RIP: 0010:[<ffffffff81b06f62>]  [<ffffffff81b06f62>] debug_check_no_obj_freed+0x1a2/0x890 lib/debugobjects.c:729
RSP: 0018:ffff8800b228fc90  EFLAGS: 00010803
RAX: 0000000000000292 RBX: 41e5894855000000 RCX: ffffffff84051f00
RDX: 12dc3d1bf1290161 RSI: 0000000000000002 RDI: ffffffff81426a8d
RBP: ffff8800b228fd78 R08: ffff8800b228fd10 R09: dead000000000200
R10: 0000000000061c80 R11: ffffffff831a49f8 R12: 96e1e8df89480b0f
R13: ffffffff840ed908 R14: 96e1e8df89480b0f R15: dffffc0000000000
FS:  000000000244d880(0063) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000421af0 CR3: 00000000b69ce000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffff8800b228fe40 ffff8800b228fdf0 ffffffff840ed900 ffff8801d2aa6000
 ffff8801d2aa50b0 0000000000000000 ffff8800b228fdb8 000000000009ba00
 fffffbfff081db20 1ffff10016451f9e ffff8801d2aa50a0 ffff8801d2aa5000
Call Trace:
 [<ffffffff8147c87f>] slab_free_hook mm/slub.c:1376 [inline]
 [<ffffffff8147c87f>] slab_free_freelist_hook mm/slub.c:1405 [inline]
 [<ffffffff8147c87f>] slab_free mm/slub.c:2859 [inline]
 [<ffffffff8147c87f>] kmem_cache_free+0x18f/0x350 mm/slub.c:2881
 [<ffffffff8195d4a9>] file_free_security security/selinux/hooks.c:306 [inline]
 [<ffffffff8195d4a9>] selinux_file_free_security+0x49/0x60 security/selinux/hooks.c:3222
 [<ffffffff8194713e>] security_file_free+0x4e/0x90 security/security.c:748
 [<ffffffff81497692>] __fput+0x242/0x6f0 fs/file_table.c:209
 [<ffffffff81497bc5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8112f8bc>] task_work_run+0x21c/0x2d0 kernel/task_work.c:115
 [<ffffffff81003edd>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff81003edd>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:188
 [<ffffffff81005784>] prepare_exit_to_usermode arch/x86/entry/common.c:221 [inline]
 [<ffffffff81005784>] syscall_return_slowpath+0x254/0x2d0 arch/x86/entry/common.c:286
 [<ffffffff82715ee1>] int_ret_from_sys_call+0x25/0xa3
Code: 48 c7 c1 00 1f 05 84 4c 8b 34 31 4d 85 f6 0f 84 aa 03 00 00 49 b9 00 02 00 00 00 00 ad de 31 f6 4c 8d 45 98 4c 89 f2 48 c1 ea 03 <42> 80 3c 3a 00 0f 85 90 03 00 00 49 8d 7e 18 83 c6 01 4d 8b 26 
RIP  [<ffffffff81b06f62>] __debug_check_no_obj_freed lib/debugobjects.c:692 [inline]
RIP  [<ffffffff81b06f62>] debug_check_no_obj_freed+0x1a2/0x890 lib/debugobjects.c:729
 RSP <ffff8800b228fc90>
---[ end trace 7cff5e28a38f99ab ]---