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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 ffff888084e7ab40 by task syz-executor.2/8472

CPU: 1 PID: 8472 Comm: syz-executor.2 Not tainted 5.0.0-next-20190305 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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_ioctl+0x239/0x300 kernel/trace/blktrace.c:730
 blkdev_ioctl+0x12c/0x1c40 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+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457f29
Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f96b422ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457f29
RDX: 0000000000000000 RSI: 0000000000001276 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f96b422f6d4
R13: 00000000004bf40c R14: 00000000004d0e58 R15: 00000000ffffffff

Allocated by task 8452:
 save_stack+0x45/0xd0 mm/kasan/common.c:75
 set_track mm/kasan/common.c:87 [inline]
 __kasan_kmalloc mm/kasan/common.c:497 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:505
 slab_post_alloc_hook mm/slab.h:436 [inline]
 slab_alloc mm/slab.c:3392 [inline]
 kmem_cache_alloc+0x11a/0x6f0 mm/slab.c:3554
 __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:1652
 lookup_one_len+0x16d/0x1a0 fs/namei.c:2541
 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: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+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7857:
 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:459
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x260 mm/slab.c:3764
 __d_free+0x20/0x30 fs/dcache.c:269
 __rcu_reclaim kernel/rcu/rcu.h:227 [inline]
 rcu_do_batch kernel/rcu/tree.c:2475 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2788 [inline]
 rcu_core+0x928/0x1390 kernel/rcu/tree.c:2769
 __do_softirq+0x266/0x95a kernel/softirq.c:293

The buggy address belongs to the object at ffff888084e7ab00
 which belongs to the cache dentry(65:syz2) of size 288
The buggy address is located 64 bytes inside of
 288-byte region [ffff888084e7ab00, ffff888084e7ac20)
The buggy address belongs to the page:
page:ffffea0002139e80 count:1 mapcount:0 mapping:ffff888088af7200 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000285f688 ffffea0002586c08 ffff888088af7200
raw: 0000000000000000 ffff888084e7a000 000000010000000b ffff88805cbded40
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88805cbded40

Memory state around the buggy address:
 ffff888084e7aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888084e7aa80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff888084e7ab00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff888084e7ab80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888084e7ac00: fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb
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