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BUG: KASAN: use-after-free in get_disk+0xb7/0xd0 block/genhd.c:1433
Read of size 8 at addr ffff8801d94f3830 by task blkid/16522

CPU: 1 PID: 16522 Comm: blkid Not tainted 4.14.67+ #1
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x11b lib/dump_stack.c:53
 print_address_description+0x60/0x22b mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.6+0x11b/0x2dd mm/kasan/report.c:409
 get_disk+0xb7/0xd0 block/genhd.c:1433
 get_gendisk+0xe4/0x230 block/genhd.c:793
 __blkdev_get+0x345/0xe50 fs/block_dev.c:1446
 blkdev_get+0x97/0x8c0 fs/block_dev.c:1604
 blkdev_open+0x1bd/0x240 fs/block_dev.c:1762
 do_dentry_open+0x426/0xda0 fs/open.c:764
 vfs_open+0x11c/0x210 fs/open.c:878
 do_last fs/namei.c:3408 [inline]
 path_openat+0x4eb/0x23a0 fs/namei.c:3550
device syz_tun entered promiscuous mode
device syz_tun left promiscuous mode
 do_filp_open+0x197/0x270 fs/namei.c:3584
 do_sys_open+0x2ef/0x580 fs/open.c:1071
 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7fa5072a9120
RSP: 002b:00007ffd88683088 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fa5072a9120
RDX: 00007ffd88683f1f RSI: 0000000000000000 RDI: 00007ffd88683f1f
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000015ad030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Allocated by task 16461:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc.part.1+0x4f/0xd0 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x138/0x300 mm/slub.c:2750
 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+0x5f/0x3b0 block/genhd.c:1387
 loop_add+0x3e9/0x840 drivers/block/loop.c:1827
 loop_control_ioctl+0x12e/0x310 drivers/block/loop.c:1959
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x1a0/0x1030 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7e/0xb0 fs/ioctl.c:692
 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 2038:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xac/0x190 mm/kasan/kasan.c:524
 slab_free_hook mm/slub.c:1389 [inline]
 slab_free_freelist_hook mm/slub.c:1410 [inline]
 slab_free mm/slub.c:2966 [inline]
 kfree+0xf5/0x310 mm/slub.c:3897
 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+0x146/0x200 lib/kobject.c:692
 put_disk+0x1f/0x30 block/genhd.c:1452
 __blkdev_get+0x564/0xe50 fs/block_dev.c:1562
 blkdev_get+0x97/0x8c0 fs/block_dev.c:1604
 blkdev_open+0x1bd/0x240 fs/block_dev.c:1762
 do_dentry_open+0x426/0xda0 fs/open.c:764
 vfs_open+0x11c/0x210 fs/open.c:878
 do_last fs/namei.c:3408 [inline]
 path_openat+0x4eb/0x23a0 fs/namei.c:3550
 do_filp_open+0x197/0x270 fs/namei.c:3584
 do_sys_open+0x2ef/0x580 fs/open.c:1071
 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801d94f3300
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1328 bytes inside of
 2048-byte region [ffff8801d94f3300, ffff8801d94f3b00)
The buggy address belongs to the page:
page:ffffea0007653c00 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000008100(slab|head)
raw: 4000000000008100 0000000000000000 0000000000000000 00000001000f000f
raw: 0000000000000000 0000000b00000001 ffff8801da802800 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d94f3700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d94f3780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d94f3800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                     ^
 ffff8801d94f3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d94f3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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