==================================================================
BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 /block/genhd.c:1543
Read of size 8 at addr ffff8801d30c2768 by task syz-executor032/2144

CPU: 0 PID: 2144 Comm: syz-executor032 Not tainted 4.4.174+ #4
 0000000000000000 2b031651ad2e3ebb ffff8800b5d3f730 ffffffff81aad1a1
 0000000000000000 ffffea00074c3000 ffff8801d30c2768 0000000000000008
 0000000000000000 ffff8800b5d3f768 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 2145:
 [<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
 [<ffffffff81d43f44>] loop_probe+0x154/0x180 /drivers/block/loop.c:1963
 [<ffffffff81d0efb1>] kobj_lookup+0x221/0x410 /drivers/base/map.c:124
 [<ffffffff81a7fe3c>] get_gendisk+0x3c/0x2e0 /block/genhd.c:689
 [<ffffffff8154ec5c>] __blkdev_get+0x39c/0xdf0 /fs/block_dev.c:1193
 [<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

Freed by task 2144:
 [<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 ffff8801d30c2200
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1384 bytes inside of
 2048-byte region [ffff8801d30c2200, ffff8801d30c2a00)
The buggy address belongs to the page:
BUG: unable to handle kernel paging request at fffff94000e98600
IP: [<ffffffff81add4d9>] memset_erms+0x9/0x10 /arch/x86/lib/memset_64.S:62
PGD 330c067 PUD 330b063 PMD 330a063 PTE 800000000330d161
Oops: 0003 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 2244 Comm: syz-executor032 Not tainted 4.4.174+ #4
task: ffff8801d3a74740 task.stack: ffff8801d4740000
RIP: 0010:[<ffffffff81add4d9>]  [<ffffffff81add4d9>] memset_erms+0x9/0x10 /arch/x86/lib/memset_64.S:62
RSP: 0018:ffff8801d4747d10  EFLAGS: 00010206
RAX: 1ffffd4000e98800 RBX: fffff94000e98800 RCX: 0000000000000200
RDX: 0000000000000200 RSI: 0000000000000000 RDI: fffff94000e98600
RBP: ffff8801d4747d28 R08: 000000000000000f R09: fffff94000e98600
R10: 00000000004002e0 R11: 0000000000000246 R12: 0000000000001000
R13: ffffea00074c3000 R14: ffffea00074c3fff R15: ffff8801da548dc0
FS:  0000000001f4e880(0063) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffff94000e98600 CR3: 00000001d4784000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff81484025 ffffea00074c4000 00000000024000c0 ffff8801d4747d68
 ffffffff8148412c ffffea00074c3fff 4000000000004080 ffff8801da548dc0
 00000000024000c0 ffffffff814ca46c ffffea00074c3000 ffff8801d4747d78
Call Trace:
 [<ffffffff8148412c>] kasan_kmalloc+0x4c/0xd0 /mm/kasan/kasan.c:611
 [<ffffffff8148475f>] kasan_slab_alloc+0xf/0x20 /mm/kasan/kasan.c:554
 [<ffffffff8147fe9c>] slab_post_alloc_hook /mm/slub.c:1349 [inline]
 [<ffffffff8147fe9c>] slab_alloc_node /mm/slub.c:2615 [inline]
 [<ffffffff8147fe9c>] slab_alloc /mm/slub.c:2623 [inline]
 [<ffffffff8147fe9c>] kmem_cache_alloc+0xdc/0x2c0 /mm/slub.c:2628
 [<ffffffff814ca46c>] getname_flags+0xcc/0x550 /fs/namei.c:135
 [<ffffffff814ca90a>] getname+0x1a/0x20 /fs/namei.c:206
 [<ffffffff8149556d>] do_sys_open+0x1fd/0x600 /fs/open.c:1032
 [<ffffffff8149599d>] SYSC_open /fs/open.c:1056 [inline]
 [<ffffffff8149599d>] SyS_open+0x2d/0x40 /fs/open.c:1051
 [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a
Code: 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 f3 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 c3 90 49 89 fa 40 0f b6 ce 48 b8 01 01 01 01 01 
RIP  [<ffffffff81add4d9>] memset_erms+0x9/0x10 /arch/x86/lib/memset_64.S:61
 RSP <ffff8801d4747d10>
CR2: fffff94000e98600
---[ end trace 00f410ea6d38c027 ]---