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BUG: KASAN: use-after-free in debugfs_remove+0x10d/0x130 fs/debugfs/inode.c:685
Read of size 8 at addr ffff88801da691e0 by task kworker/1:1/22

CPU: 1 PID: 22 Comm: kworker/1:1 Not tainted 5.0.0-rc5-next-20190207 #30
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:317
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 debugfs_remove+0x10d/0x130 fs/debugfs/inode.c:685
 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:752
 __blk_release_queue+0x1dc/0x3a0 block/blk-sysfs.c:866
 process_one_work+0x98e/0x1790 kernel/workqueue.c:2267
 worker_thread+0x98/0xe40 kernel/workqueue.c:2413
 kthread+0x357/0x430 kernel/kthread.c:247
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Allocated by task 10841:
 save_stack+0x45/0xd0 mm/kasan/common.c:75
 set_track mm/kasan/common.c:87 [inline]
 __kasan_kmalloc mm/kasan/common.c:498 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:471
 kasan_kmalloc mm/kasan/common.c:506 [inline]
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:413
 kmem_cache_alloc+0x12d/0x710 mm/slab.c:3543
 __d_alloc+0x2e/0x8c0 fs/dcache.c:1622
 d_alloc+0x4d/0x2b0 fs/dcache.c:1701
 d_alloc_parallel+0xf4/0x1bc0 fs/dcache.c:2449
 __lookup_slow+0x1ab/0x500 fs/namei.c:1654
 lookup_one_len+0x16d/0x1a0 fs/namei.c:2543
 start_creating fs/debugfs/inode.c:308 [inline]
 start_creating+0xbf/0x1e0 fs/debugfs/inode.c:284
 __debugfs_create_file+0x65/0x400 fs/debugfs/inode.c:347
 debugfs_create_file+0x5a/0x70 fs/debugfs/inode.c:400
 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+0x12c/0x1c40 block/ioctl.c:591
 block_ioctl+0xee/0x130 fs/block_dev.c:1914
 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+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 9:
 save_stack+0x45/0xd0 mm/kasan/common.c:75
 set_track mm/kasan/common.c:87 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:460
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:468
 __cache_free mm/slab.c:3487 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3749
 __d_free+0x20/0x30 fs/dcache.c:269
 __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
 rcu_do_batch kernel/rcu/tree.c:2486 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2799 [inline]
 rcu_core+0x928/0x1390 kernel/rcu/tree.c:2780
 __do_softirq+0x266/0x95a kernel/softirq.c:292

The buggy address belongs to the object at ffff88801da691a0
 which belongs to the cache dentry(81:syz4) of size 288
The buggy address is located 64 bytes inside of
 288-byte region [ffff88801da691a0, ffff88801da692c0)
The buggy address belongs to the page:
page:ffffea0000769a40 count:1 mapcount:0 mapping:ffff888033780a80 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffff888014635a48 ffffea0000763748 ffff888033780a80
raw: 0000000000000000 ffff88801da69040 000000010000000b ffff8880880b4b80
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8880880b4b80

Memory state around the buggy address:
 ffff88801da69080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801da69100: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88801da69180: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff88801da69200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801da69280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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