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BUG: KASAN: use-after-free in debugfs_remove+0x10d/0x130 fs/debugfs/inode.c:690
Read of size 8 at addr ffff888084c8f7a0 by task kworker/0:0/5

CPU: 0 PID: 5 Comm: kworker/0:0 Not tainted 5.1.0-rc6-next-20190426 #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events __blk_release_queue
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
 __kasan_report.cold+0x1b/0x40 mm/kasan/report.c:316
 kasan_report+0x12/0x20 mm/kasan/common.c:620
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 debugfs_remove+0x10d/0x130 fs/debugfs/inode.c:690
 blk_trace_free+0x38/0x140 kernel/trace/blktrace.c:312
 blk_trace_cleanup kernel/trace/blktrace.c:339 [inline]
 __blk_trace_remove+0x78/0xa0 kernel/trace/blktrace.c:352
 blk_trace_shutdown+0x67/0x90 kernel/trace/blktrace.c:753
 __blk_release_queue+0x1dc/0x3a0 block/blk-sysfs.c:885
 process_one_work+0x98e/0x1790 kernel/workqueue.c:2268
 worker_thread+0x98/0xe40 kernel/workqueue.c:2414
 kthread+0x357/0x430 kernel/kthread.c:254
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Allocated by task 24390:
 save_stack+0x45/0xb0 mm/kasan/common.c:76
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:468
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:503
 slab_post_alloc_hook mm/slab.h:437 [inline]
 slab_alloc mm/slab.c:3356 [inline]
 kmem_cache_alloc+0x11a/0x6f0 mm/slab.c:3518
 __d_alloc+0x2e/0x8c0 fs/dcache.c:1623
 d_alloc+0x4d/0x280 fs/dcache.c:1702
 d_alloc_parallel+0xf4/0x1bc0 fs/dcache.c:2456
 __lookup_slow+0x1ab/0x500 fs/namei.c:1652
 lookup_one_len+0x16d/0x1a0 fs/namei.c:2541
 start_creating fs/debugfs/inode.c:313 [inline]
 start_creating+0xbf/0x1e0 fs/debugfs/inode.c:289
 __debugfs_create_file+0x65/0x400 fs/debugfs/inode.c:352
 debugfs_create_file+0x5a/0x70 fs/debugfs/inode.c:405
 do_blk_trace_setup+0x376/0xb90 kernel/trace/blktrace.c:528
 __blk_trace_setup+0xe3/0x190 kernel/trace/blktrace.c:577
 blk_trace_ioctl+0x170/0x300 kernel/trace/blktrace.c:716
 blkdev_ioctl+0x276/0x1d10 block/ioctl.c:591
 block_ioctl+0xee/0x130 fs/block_dev.c:1931
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd6e/0x1390 fs/ioctl.c:696
 ksys_ioctl+0xab/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+0x103/0x670 arch/x86/entry/common.c:298
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 24394:
 save_stack+0x45/0xb0 mm/kasan/common.c:76
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:457
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:465
 __cache_free mm/slab.c:3462 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3728
 __d_free+0x20/0x30 fs/dcache.c:270
 __rcu_reclaim kernel/rcu/rcu.h:222 [inline]
 rcu_do_batch kernel/rcu/tree.c:2092 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2310 [inline]
 rcu_core+0xbac/0x1510 kernel/rcu/tree.c:2291
 __do_softirq+0x266/0x95a kernel/softirq.c:293

The buggy address belongs to the object at ffff888084c8f760
 which belongs to the cache dentry(17:syz0) of size 288
The buggy address is located 64 bytes inside of
 288-byte region [ffff888084c8f760, ffff888084c8f880)
The buggy address belongs to the page:
page:ffffea00021323c0 count:1 mapcount:0 mapping:ffff88809ae3e200 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0001562e88 ffffea0001561888 ffff88809ae3e200
raw: 0000000000000000 ffff888084c8f080 000000010000000b ffff8880625d9140
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8880625d9140

Memory state around the buggy address:
 ffff888084c8f680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888084c8f700: 00 00 00 00 fc fc fc fc fc fc fc fc fb fb fb fb
>ffff888084c8f780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888084c8f800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888084c8f880: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
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