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BUG: KASAN: use-after-free in get_disk_and_module+0xd5/0xf0 block/genhd.c:1484
Read of size 8 at addr ffff8881d49c8598 by task blkid/9191

CPU: 0 PID: 9191 Comm: blkid Not tainted 4.20.0-rc6+ #151
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 get_disk_and_module+0xd5/0xf0 block/genhd.c:1484
 get_gendisk+0x17a/0x380 block/genhd.c:842
 bdev_get_gendisk fs/block_dev.c:1066 [inline]
 __blkdev_get+0x467/0x13c0 fs/block_dev.c:1461
 blkdev_get+0xc1/0xb50 fs/block_dev.c:1617
 blkdev_open+0x1fb/0x280 fs/block_dev.c:1775
 do_dentry_open+0x499/0x1250 fs/open.c:771
 vfs_open+0xa0/0xd0 fs/open.c:880
 do_last fs/namei.c:3418 [inline]
 path_openat+0x12bc/0x5150 fs/namei.c:3534
 do_filp_open+0x255/0x380 fs/namei.c:3564
 do_sys_open+0x568/0x700 fs/open.c:1063
 __do_sys_open fs/open.c:1081 [inline]
 __se_sys_open fs/open.c:1076 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1076
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f85b5d06120
Code: 48 8b 15 1b 4d 2b 00 f7 d8 64 89 02 83 c8 ff c3 90 90 90 90 90 90 90 90 90 90 83 3d d5 a4 2b 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 5e 8c 01 00 48 89 04 24
RSP: 002b:00007ffd5aa58578 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f85b5d06120
RDX: 00007ffd5aa58f1a RSI: 0000000000000000 RDI: 00007ffd5aa58f1a
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000716030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Allocated by task 6060:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 kmem_cache_alloc_node_trace+0x14c/0x740 mm/slab.c:3663
 kmalloc_node include/linux/slab.h:584 [inline]
 kzalloc_node include/linux/slab.h:752 [inline]
 __alloc_disk_node+0xc9/0x510 block/genhd.c:1437
 loop_add+0x459/0xa40 drivers/block/loop.c:1873
 loop_probe+0x18d/0x1d0 drivers/block/loop.c:1980
 kobj_lookup+0x264/0x460 drivers/base/map.c:124
 get_gendisk+0x4c/0x380 block/genhd.c:834
 bdev_get_gendisk fs/block_dev.c:1066 [inline]
 __blkdev_get+0x467/0x13c0 fs/block_dev.c:1461
 blkdev_get+0xc1/0xb50 fs/block_dev.c:1617
 blkdev_open+0x1fb/0x280 fs/block_dev.c:1775
 do_dentry_open+0x499/0x1250 fs/open.c:771
 vfs_open+0xa0/0xd0 fs/open.c:880
 do_last fs/namei.c:3418 [inline]
 path_openat+0x12bc/0x5150 fs/namei.c:3534
 do_filp_open+0x255/0x380 fs/namei.c:3564
 do_sys_open+0x568/0x700 fs/open.c:1063
 __do_sys_open fs/open.c:1081 [inline]
 __se_sys_open fs/open.c:1076 [inline]
 __x64_sys_open+0x7e/0xc0 fs/open.c:1076
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9190:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xcf/0x230 mm/slab.c:3817
 disk_release+0x1f2/0x250 block/genhd.c:1291
 device_release+0x7e/0x210 drivers/base/core.c:891
 kobject_cleanup lib/kobject.c:662 [inline]
 kobject_release lib/kobject.c:691 [inline]
 kref_put include/linux/kref.h:70 [inline]
 kobject_put.cold.9+0x287/0x2e4 lib/kobject.c:708
 put_disk+0x23/0x30 block/genhd.c:1502
 loop_remove+0x92/0xc0 drivers/block/loop.c:1929
 loop_control_ioctl+0x48b/0x530 drivers/block/loop.c:2027
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881d49c8040
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1368 bytes inside of
 2048-byte region [ffff8881d49c8040, ffff8881d49c8840)
The buggy address belongs to the page:
page:ffffea0007527200 count:1 mapcount:0 mapping:ffff8881da800c40 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea00070c6d08 ffffea0006de2308 ffff8881da800c40
raw: 0000000000000000 ffff8881d49c8040 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881d49c8480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881d49c8500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881d49c8580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8881d49c8600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881d49c8680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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