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BUG: KASAN: use-after-free in disk_unblock_events+0x55/0x60 /block/genhd.c:1550
Read of size 8 at addr ffff8801cde39660 by task blkid/2120

CPU: 0 PID: 2120 Comm: blkid Not tainted 4.9.185+ #8
 ffff8801c570f730 ffffffff81b5a081 0000000000000000 ffffea0007378e00
 ffff8801cde39660 0000000000000008 ffffffff81b2c645 ffff8801c570f768
 ffffffff8150ab38 0000000000000000 ffff8801cde39660 ffff8801cde39660
Call Trace:
 [<00000000f248a565>] __dump_stack /lib/dump_stack.c:15 [inline]
 [<00000000f248a565>] dump_stack+0xc1/0x120 /lib/dump_stack.c:51
 [<000000006cf5954c>] print_address_description+0x6f/0x23a /mm/kasan/report.c:256
 [<00000000af243fda>] kasan_report_error /mm/kasan/report.c:355 [inline]
 [<00000000af243fda>] kasan_report /mm/kasan/report.c:413 [inline]
 [<00000000af243fda>] kasan_report.cold+0x8c/0x2ba /mm/kasan/report.c:397
 [<0000000052fb1aa5>] __asan_report_load8_noabort+0x14/0x20 /mm/kasan/report.c:434
 [<00000000bfbd0bb7>] disk_unblock_events+0x55/0x60 /block/genhd.c:1550
 [<000000005f46b2db>] __blkdev_get+0x6ba/0xeb0 /fs/block_dev.c:1368
 [<00000000dd9e16c4>] blkdev_get+0x2e8/0x920 /fs/block_dev.c:1424
 [<000000002474a7fc>] blkdev_open+0x1aa/0x250 /fs/block_dev.c:1579
 [<00000000931fbfff>] do_dentry_open+0x422/0xd20 /fs/open.c:772
 [<0000000074bdb841>] vfs_open+0x105/0x230 /fs/open.c:885
 [<00000000df798a40>] do_last /fs/namei.c:3457 [inline]
 [<00000000df798a40>] path_openat+0xbf5/0x2f60 /fs/namei.c:3581
 [<00000000a803ec6e>] do_filp_open+0x1a1/0x280 /fs/namei.c:3615
 [<0000000084cd3b6b>] do_sys_open+0x2f0/0x610 /fs/open.c:1078
 [<000000004cbbe805>] SYSC_open /fs/open.c:1096 [inline]
 [<000000004cbbe805>] SyS_open+0x2d/0x40 /fs/open.c:1091
 [<0000000035a8a78e>] do_syscall_64+0x1ad/0x5c0 /arch/x86/entry/common.c:288
 [<000000009514bdb1>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 2111:
 save_stack_trace+0x16/0x20 /arch/x86/kernel/stacktrace.c:57
 save_stack /mm/kasan/kasan.c:512 [inline]
 set_track /mm/kasan/kasan.c:524 [inline]
 kasan_kmalloc.part.0+0x62/0xf0 /mm/kasan/kasan.c:616
 kasan_kmalloc+0xb7/0xd0 /mm/kasan/kasan.c:601
 kmem_cache_alloc_trace+0x115/0x2d0 /mm/slub.c:2742
 kmem_cache_alloc_node_trace /./include/linux/slab.h:381 [inline]
 kmalloc_node /./include/linux/slab.h:528 [inline]
 kzalloc_node /./include/linux/slab.h:647 [inline]
 alloc_disk_node+0x50/0x3c0 /block/genhd.c:1294
 alloc_disk+0x1b/0x20 /block/genhd.c:1286
 loop_add+0x37e/0x7d0 /drivers/block/loop.c:1849
 loop_probe+0x154/0x180 /drivers/block/loop.c:1956
 kobj_lookup+0x221/0x410 /drivers/base/map.c:124
 get_gendisk+0x3c/0x2d0 /block/genhd.c:716
 __blkdev_get+0x356/0xeb0 /fs/block_dev.c:1267
 blkdev_get+0x2e8/0x920 /fs/block_dev.c:1424
 blkdev_open+0x1aa/0x250 /fs/block_dev.c:1579
 do_dentry_open+0x422/0xd20 /fs/open.c:772
 vfs_open+0x105/0x230 /fs/open.c:885
 do_last /fs/namei.c:3457 [inline]
 path_openat+0xbf5/0x2f60 /fs/namei.c:3581
 do_filp_open+0x1a1/0x280 /fs/namei.c:3615
 do_sys_open+0x2f0/0x610 /fs/open.c:1078
 SYSC_open /fs/open.c:1096 [inline]
 SyS_open+0x2d/0x40 /fs/open.c:1091
 do_syscall_64+0x1ad/0x5c0 /arch/x86/entry/common.c:288
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 2120:
 save_stack_trace+0x16/0x20 /arch/x86/kernel/stacktrace.c:57
 save_stack /mm/kasan/kasan.c:512 [inline]
 set_track /mm/kasan/kasan.c:524 [inline]
 kasan_slab_free+0xb0/0x190 /mm/kasan/kasan.c:589
 slab_free_hook /mm/slub.c:1355 [inline]
 slab_free_freelist_hook /mm/slub.c:1377 [inline]
 slab_free /mm/slub.c:2958 [inline]
 kfree+0xfc/0x310 /mm/slub.c:3878
 disk_release+0x255/0x330 /block/genhd.c:1147
 device_release+0x7d/0x220 /drivers/base/core.c:247
 kobject_cleanup /lib/kobject.c:643 [inline]
 kobject_release /lib/kobject.c:672 [inline]
 kref_sub /./include/linux/kref.h:73 [inline]
 kref_put /./include/linux/kref.h:98 [inline]
 kobject_put+0x150/0x260 /lib/kobject.c:689
 put_disk+0x23/0x30 /block/genhd.c:1358
 __blkdev_get+0x61a/0xeb0 /fs/block_dev.c:1361
 blkdev_get+0x2e8/0x920 /fs/block_dev.c:1424
 blkdev_open+0x1aa/0x250 /fs/block_dev.c:1579
 do_dentry_open+0x422/0xd20 /fs/open.c:772
 vfs_open+0x105/0x230 /fs/open.c:885
 do_last /fs/namei.c:3457 [inline]
 path_openat+0xbf5/0x2f60 /fs/namei.c:3581
 do_filp_open+0x1a1/0x280 /fs/namei.c:3615
 do_sys_open+0x2f0/0x610 /fs/open.c:1078
 SYSC_open /fs/open.c:1096 [inline]
 SyS_open+0x2d/0x40 /fs/open.c:1091
 do_syscall_64+0x1ad/0x5c0 /arch/x86/entry/common.c:288
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the object at ffff8801cde39100
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1376 bytes inside of
 2048-byte region [ffff8801cde39100, ffff8801cde39900)
The buggy address belongs to the page:
page:ffffea0007378e00 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cde39500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cde39580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801cde39600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8801cde39680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cde39700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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