BUG: KASAN: use-after-free in disk_unblock_events+0x51/0x60 block/genhd.c:1632
Read of size 8 at addr ffff88006d378b40 by task blkid/3172

CPU: 0 PID: 3172 Comm: blkid Not tainted 4.14.0-rc5-next-20171018+ #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 disk_unblock_events+0x51/0x60 block/genhd.c:1632
 __blkdev_get+0x78d/0xf90 fs/block_dev.c:1535
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1591
 blkdev_open+0x1c9/0x250 fs/block_dev.c:1749
 do_dentry_open+0x664/0xd40 fs/open.c:752
 vfs_open+0x107/0x220 fs/open.c:866
 do_last fs/namei.c:3387 [inline]
 path_openat+0x1151/0x3520 fs/namei.c:3527
 do_filp_open+0x25b/0x3b0 fs/namei.c:3562
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x7f429a253120
RSP: 002b:00007ffd02d12378 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f429a253120
RDX: 00007ffd02d12f45 RSI: 0000000000000000 RDI: 00007ffd02d12f45
RBP: 0000000000000082 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000166f030
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000005

Allocated by task 3165:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_node_trace+0x150/0x750 mm/slab.c:3657
 kmalloc_node include/linux/slab.h:540 [inline]
 kzalloc_node include/linux/slab.h:702 [inline]
 alloc_disk_node+0xb4/0x4e0 block/genhd.c:1375
 alloc_disk+0x18/0x20 block/genhd.c:1359
 loop_add+0x45c/0xa50 drivers/block/loop.c:1808
 loop_probe+0x16d/0x1a0 drivers/block/loop.c:1915
 kobj_lookup+0x2ac/0x410 drivers/base/map.c:124
 get_gendisk+0x37/0x230 block/genhd.c:773
 bd_start_claiming fs/block_dev.c:1097 [inline]
 blkdev_get+0x12d/0xad0 fs/block_dev.c:1584
 blkdev_open+0x1c9/0x250 fs/block_dev.c:1749
 do_dentry_open+0x664/0xd40 fs/open.c:752
 vfs_open+0x107/0x220 fs/open.c:866
 do_last fs/namei.c:3387 [inline]
 path_openat+0x1151/0x3520 fs/namei.c:3527
 do_filp_open+0x25b/0x3b0 fs/namei.c:3562
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 3172:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3492 [inline]
 kfree+0xca/0x250 mm/slab.c:3807
 disk_release+0x327/0x410 block/genhd.c:1218
 device_release+0x7c/0x200 drivers/base/core.c:814
 kobject_cleanup lib/kobject.c:648 [inline]
 kobject_release lib/kobject.c:677 [inline]
 kref_put include/linux/kref.h:70 [inline]
 kobject_put+0x14c/0x240 lib/kobject.c:694
 put_disk+0x23/0x30 block/genhd.c:1440
 __blkdev_get+0x6ed/0xf90 fs/block_dev.c:1528
 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1591
 blkdev_open+0x1c9/0x250 fs/block_dev.c:1749
 do_dentry_open+0x664/0xd40 fs/open.c:752
 vfs_open+0x107/0x220 fs/open.c:866
 do_last fs/namei.c:3387 [inline]
 path_openat+0x1151/0x3520 fs/namei.c:3527
 do_filp_open+0x25b/0x3b0 fs/namei.c:3562
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x1f/0xbe

The buggy address belongs to the object at ffff88006d3785c0
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1408 bytes inside of
 2048-byte region [ffff88006d3785c0, ffff88006d378dc0)
The buggy address belongs to the page:
page:ffffea0001b4de00 count:1 mapcount:0 mapping:ffff88006d3785c0 index:0x0 compound_mapcount: 0
flags: 0x500000000008100(slab|head)
raw: 0500000000008100 ffff88006d3785c0 0000000000000000 0000000100000003
raw: ffffea0001b46920 ffffea0001a322a0 ffff88003e800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88006d378a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88006d378a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88006d378b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff88006d378b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88006d378c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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