==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 block/genhd.c:1644
Read of size 8 at addr ffff88809e143408 by task syz-executor996/12738

CPU: 1 PID: 12738 Comm: syz-executor996 Not tainted 4.14.128 #22
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x138/0x19c lib/dump_stack.c:53
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 disk_unblock_events+0x55/0x60 block/genhd.c:1644
 __blkdev_get+0x7d6/0x1120 fs/block_dev.c:1556
 blkdev_get+0xa8/0x8e0 fs/block_dev.c:1612
 blkdev_open+0x1d1/0x260 fs/block_dev.c:1770
 do_dentry_open+0x73b/0xeb0 fs/open.c:758
 vfs_open+0x105/0x220 fs/open.c:872
 do_last fs/namei.c:3425 [inline]
 path_openat+0x8bd/0x3f70 fs/namei.c:3566
 do_filp_open+0x18e/0x250 fs/namei.c:3600
 do_sys_open+0x2c5/0x430 fs/open.c:1065
 SYSC_open fs/open.c:1083 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1078
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x405781
RSP: 002b:00007f0824a99980 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000405781
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f0824a99990
RBP: 6666666666666667 R08: 000000000000000f R09: 00007f0824a9a700
R10: 00007f0824a9a9d0 R11: 0000000000000293 R12: 00000000006dbc4c
R13: 00007ffc5422fb2f R14: 00007f0824a9a9c0 R15: 000000000000002d

Allocated by task 12738:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 kmem_cache_alloc_node_trace+0x153/0x770 mm/slab.c:3661
 kmalloc_node include/linux/slab.h:526 [inline]
 kzalloc_node include/linux/slab.h:672 [inline]
 alloc_disk_node+0x64/0x3e0 block/genhd.c:1387
 alloc_disk+0x1b/0x20 block/genhd.c:1371
 loop_add+0x3e7/0x850 drivers/block/loop.c:1858
 loop_probe+0x136/0x160 drivers/block/loop.c:1965
 kobj_lookup+0x21c/0x400 drivers/base/map.c:124
 get_gendisk+0x3b/0x240 block/genhd.c:785
 __blkdev_get+0x3af/0x1120 fs/block_dev.c:1451
 blkdev_get+0xa8/0x8e0 fs/block_dev.c:1612
 blkdev_open+0x1d1/0x260 fs/block_dev.c:1770
 do_dentry_open+0x73b/0xeb0 fs/open.c:758
 vfs_open+0x105/0x220 fs/open.c:872
 do_last fs/namei.c:3425 [inline]
 path_openat+0x8bd/0x3f70 fs/namei.c:3566
 do_filp_open+0x18e/0x250 fs/namei.c:3600
 do_sys_open+0x2c5/0x430 fs/open.c:1065
 SYSC_open fs/open.c:1083 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1078
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 12738:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 disk_release+0x24b/0x2d0 block/genhd.c:1230
 device_release+0xf6/0x1a0 drivers/base/core.c:822
 kobject_cleanup lib/kobject.c:646 [inline]
 kobject_release lib/kobject.c:675 [inline]
 kref_put include/linux/kref.h:70 [inline]
 kobject_put.cold+0x269/0x2f9 lib/kobject.c:692
 put_disk+0x23/0x30 block/genhd.c:1452
 __blkdev_get+0x73c/0x1120 fs/block_dev.c:1549
 blkdev_get+0xa8/0x8e0 fs/block_dev.c:1612
 blkdev_open+0x1d1/0x260 fs/block_dev.c:1770
 do_dentry_open+0x73b/0xeb0 fs/open.c:758
 vfs_open+0x105/0x220 fs/open.c:872
 do_last fs/namei.c:3425 [inline]
 path_openat+0x8bd/0x3f70 fs/namei.c:3566
 do_filp_open+0x18e/0x250 fs/namei.c:3600
 do_sys_open+0x2c5/0x430 fs/open.c:1065
 SYSC_open fs/open.c:1083 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1078
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff88809e142e80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1416 bytes inside of
 2048-byte region [ffff88809e142e80, ffff88809e143680)
The buggy address belongs to the page:
page:ffffea0002785080 count:1 mapcount:0 mapping:ffff88809e142600 index:0x0 compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffff88809e142600 0000000000000000 0000000100000003
raw: ffffea00027182a0 ffffea00021533a0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809e143300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809e143380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809e143400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88809e143480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809e143500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================