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BUG: KASAN: use-after-free in get_disk+0xc0/0xd0 block/genhd.c:1433
Read of size 8 at addr ffff88819f40f3b0 by task blkid/8661

CPU: 1 PID: 8661 Comm: blkid Not tainted 4.14.138+ #30
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xca/0x134 lib/dump_stack.c:53
 print_address_description+0x60/0x226 mm/kasan/report.c:187
 __kasan_report.cold+0x1a/0x41 mm/kasan/report.c:316
 get_disk+0xc0/0xd0 block/genhd.c:1433
 get_gendisk block/genhd.c:793 [inline]
 get_gendisk+0xee/0x240 block/genhd.c:778
 __blkdev_get+0x345/0xf90 fs/block_dev.c:1451
 blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
 blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
 do_dentry_open+0x44e/0xe20 fs/open.c:789
 vfs_open+0x105/0x230 fs/open.c:903
 do_last fs/namei.c:3455 [inline]
 path_openat+0xb6c/0x2be0 fs/namei.c:3597
 do_filp_open+0x1a1/0x280 fs/namei.c:3631
 do_sys_open+0x2ca/0x590 fs/open.c:1096
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f1114c0d120
RSP: 002b:00007ffe1db0e348 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1114c0d120
RDX: 00007ffe1db0ef20 RSI: 0000000000000000 RDI: 00007ffe1db0ef20
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000062a030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Allocated by task 8640:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc.part.0+0x53/0xc0 mm/kasan/common.c:495
 kmem_cache_alloc_node_trace include/linux/slab.h:378 [inline]
 kmalloc_node include/linux/slab.h:526 [inline]
 kzalloc_node include/linux/slab.h:672 [inline]
 alloc_disk_node+0x5b/0x3d0 block/genhd.c:1387
 loop_add+0x3ee/0x870 drivers/block/loop.c:1858
 loop_probe+0x153/0x180 drivers/block/loop.c:1965
 kobj_lookup+0x226/0x410 drivers/base/map.c:124
 get_gendisk+0x36/0x240 block/genhd.c:785
 __blkdev_get+0x345/0xf90 fs/block_dev.c:1451
 blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
 blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
 do_dentry_open+0x44e/0xe20 fs/open.c:789
 vfs_open+0x105/0x230 fs/open.c:903
 do_last fs/namei.c:3455 [inline]
 path_openat+0xb6c/0x2be0 fs/namei.c:3597
 do_filp_open+0x1a1/0x280 fs/namei.c:3631
 do_sys_open+0x2ca/0x590 fs/open.c:1096
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

Freed by task 8644:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x164/0x210 mm/kasan/common.c:457
 slab_free_hook mm/slub.c:1403 [inline]
 slab_free_freelist_hook mm/slub.c:1430 [inline]
 slab_free mm/slub.c:3005 [inline]
 kfree+0xfa/0x320 mm/slub.c:3942
 device_release+0xf4/0x1a0 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+0x142/0x200 lib/kobject.c:692
 put_disk+0x1f/0x30 block/genhd.c:1452
 __blkdev_get+0x564/0xf90 fs/block_dev.c:1570
 blkdev_get+0x97/0x8b0 fs/block_dev.c:1612
 blkdev_open+0x1cc/0x250 fs/block_dev.c:1770
 do_dentry_open+0x44e/0xe20 fs/open.c:789
 vfs_open+0x105/0x230 fs/open.c:903
 do_last fs/namei.c:3455 [inline]
 path_openat+0xb6c/0x2be0 fs/namei.c:3597
 do_filp_open+0x1a1/0x280 fs/namei.c:3631
 do_sys_open+0x2ca/0x590 fs/open.c:1096
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

The buggy address belongs to the object at ffff88819f40ee80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1328 bytes inside of
 2048-byte region [ffff88819f40ee80, ffff88819f40f680)
The buggy address belongs to the page:
page:ffffea00067d0200 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000000000000 00000001000f000f
raw: dead000000000100 dead000000000200 ffff8881da802800 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88819f40f280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88819f40f300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88819f40f380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff88819f40f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88819f40f480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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