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BUG: KASAN: use-after-free in get_disk+0xc2/0xd0 block/genhd.c:1339
Read of size 8 at addr ffff8801d78773a8 by task blkid/15129

CPU: 0 PID: 15129 Comm: blkid Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801bd897698 ffffffff81eb4be9 ffffea00075e1c00 ffff8801d78773a8
 0000000000000000 ffff8801d78773a8 0000000000000000 ffff8801bd8976d0
 ffffffff81567f89 ffff8801d78773a8 0000000000000008 0000000000000000
Call Trace:
 [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81567f89>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff81568393>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff81568393>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153bf14>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff81e5b8b2>] get_disk+0xc2/0xd0 block/genhd.c:1339
 [<ffffffff81e5bbca>] get_gendisk+0x16a/0x2d0 block/genhd.c:724
 [<ffffffff81631a41>] __blkdev_get+0x351/0xd60 fs/block_dev.c:1262
 [<ffffffff81634cea>] blkdev_get+0x2da/0x920 fs/block_dev.c:1416
 [<ffffffff81635545>] blkdev_open+0x1a5/0x250 fs/block_dev.c:1571
 [<ffffffff8156a103>] do_dentry_open+0x703/0xc80 fs/open.c:766
 [<ffffffff8156d8ec>] vfs_open+0x11c/0x210 fs/open.c:879
 [<ffffffff815a4a28>] do_last fs/namei.c:3410 [inline]
 [<ffffffff815a4a28>] path_openat+0x758/0x3590 fs/namei.c:3534
 [<ffffffff815abb27>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e2fd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e5dd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156e5dd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Allocated by task 15047:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:609
 kmem_cache_alloc_trace+0xfd/0x2b0 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+0x54/0x3a0 block/genhd.c:1294
 alloc_disk+0x18/0x20 block/genhd.c:1286
 loop_add+0x33b/0x770 drivers/block/loop.c:1791
 loop_control_ioctl+0x136/0x300 drivers/block/loop.c:1923
 vfs_ioctl fs/ioctl.c:43 [inline]
 file_ioctl fs/ioctl.c:493 [inline]
 do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 SYSC_ioctl fs/ioctl.c:694 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 15071:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack+0x43/0xd0 mm/kasan/kasan.c:505
 set_track mm/kasan/kasan.c:517 [inline]
 kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:582
 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+0xfb/0x310 mm/slub.c:3878
 disk_release+0x259/0x330 block/genhd.c:1147
 device_release+0x7e/0x220 drivers/base/core.c:247
 kobject_cleanup lib/kobject.c:643 [inline]
 kobject_release+0x103/0x1b0 lib/kobject.c:672
 kref_sub include/linux/kref.h:73 [inline]
 kref_put include/linux/kref.h:98 [inline]
 kobject_put+0x6d/0xd0 lib/kobject.c:689
 put_disk+0x23/0x30 block/genhd.c:1358
 loop_remove+0x92/0xc0 drivers/block/loop.c:1847
 loop_control_ioctl+0x2b1/0x300 drivers/block/loop.c:1943
 vfs_ioctl fs/ioctl.c:43 [inline]
 file_ioctl fs/ioctl.c:493 [inline]
 do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 SYSC_ioctl fs/ioctl.c:694 [inline]
 SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the object at ffff8801d7876e80
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1320 bytes inside of
 2048-byte region [ffff8801d7876e80, ffff8801d7877680)
The buggy address belongs to the page:
page:ffffea00075e1c00 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000004080(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d7877280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d7877300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801d7877380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801d7877400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d7877480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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