==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1543
Read of size 8 at addr ffff8801d1eb7c68 by task syz-executor666/2300

CPU: 1 PID: 2300 Comm: syz-executor666 Not tainted 4.4.174+ #17
 0000000000000000 77d312ca725825a2 ffff8800b21076c0 ffffffff81aad1a1
 0000000000000000 ffffea000747ac00 ffff8801d1eb7c68 0000000000000008
 0000000000000000 ffff8800b21076f8 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
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] 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
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

Allocated by task 2300:
 [<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 2300:
 [<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
 [<ffffffff81599c4a>] C_SYSC_open fs/compat.c:1092 [inline]
 [<ffffffff81599c4a>] 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
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

The buggy address belongs to the object at ffff8801d1eb7700
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d1eb7700, ffff8801d1eb7f00)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at fffffffe12764440
IP: [<ffffffff811f471e>] cpuacct_charge+0x14e/0x360 kernel/sched/cpuacct.c:247
PGD 2e0d067 PUD 0 
Oops: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 2382 Comm: blkid Not tainted 4.4.174+ #17
task: ffff8801d0a92f80 task.stack: ffff8800b34b8000
RIP: 0010:[<ffffffff811f471e>]  [<ffffffff811f471e>] cpuacct_charge+0x14e/0x360 kernel/sched/cpuacct.c:247
RSP: 0018:ffff8800b34bf7b8  EFLAGS: 00010046
RAX: 1ffffffff05d2a33 RBX: 00000000000181a8 RCX: fffffffe12764440
RDX: fffffbffc24ec888 RSI: ffffffff81b0abec RDI: ffffffff82e95198
RBP: ffff8800b34bf7f8 R08: 0000000000000002 R09: ffff8801d0a938b8
R10: ffffffff82836880 R11: 0000000000000000 R12: ffffffff82e950c0
R13: dffffc0000000000 R14: 000000004ae76d63 R15: ffffffffd1eb7f00
FS:  00007f71b7fda740(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffffe12764440 CR3: 00000001d4a0e000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff811f4630 0000000000000046 0000000000000003 ffff8801d1f02fe0
 ffff8801d1f02f80 000000004ae76d63 ffff8801d1f03030 0000000000000000
 ffff8800b34bf840 ffffffff8117c4a3 ffff880100000001 0000000000000000
Call Trace:
 [<ffffffff8117c4a3>] update_curr+0x2c3/0x6e0 kernel/sched/fair.c:882
 [<ffffffff811ae55f>] dequeue_entity kernel/sched/fair.c:3588 [inline]
 [<ffffffff811ae55f>] dequeue_task_fair+0x7f/0x86a0 kernel/sched/fair.c:4791
 [<ffffffff81163c39>] dequeue_task kernel/sched/core.c:866 [inline]
 [<ffffffff81163c39>] deactivate_task+0x229/0x2e0 kernel/sched/core.c:882
 [<ffffffff8117d702>] detach_task+0x82/0x370 kernel/sched/fair.c:7568
 [<ffffffff811c686b>] detach_tasks kernel/sched/fair.c:7658 [inline]
 [<ffffffff811c686b>] load_balance+0xc7b/0x3050 kernel/sched/fair.c:9079
 [<ffffffff811c9f11>] idle_balance kernel/sched/fair.c:9344 [inline]
 [<ffffffff811c9f11>] pick_next_task_fair+0x4e1/0x1fa0 kernel/sched/fair.c:7147
 [<ffffffff82707d7a>] pick_next_task kernel/sched/core.c:3178 [inline]
 [<ffffffff82707d7a>] __schedule+0x32a/0x1ee0 kernel/sched/core.c:3308
 [<ffffffff82709b79>] schedule+0x99/0x1d0 kernel/sched/core.c:3355
 [<ffffffff810d9a1e>] do_exit+0x17de/0x2c60 kernel/exit.c:843
 [<ffffffff810df091>] do_group_exit+0x111/0x300 kernel/exit.c:893
 [<ffffffff810df29d>] SYSC_exit_group kernel/exit.c:904 [inline]
 [<ffffffff810df29d>] SyS_exit_group+0x1d/0x20 kernel/exit.c:902
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: 49 8d bc 24 d8 00 00 00 48 89 f8 48 c1 e8 03 42 80 3c 28 00 0f 85 ba 01 00 00 49 8b 9c 24 d8 00 00 00 80 3a 00 0f 85 8c 01 00 00 <4a> 03 1c fd 40 4c 1a 83 48 89 d8 48 c1 e8 03 42 80 3c 28 00 0f 
RIP  [<ffffffff811f471e>] cpuacct_charge+0x14e/0x360 kernel/sched/cpuacct.c:247
 RSP <ffff8800b34bf7b8>
CR2: fffffffe12764440
---[ end trace f231d806a42579e5 ]---