bisecting fixing commit since ddef1e8e3f6eb26034833b7255e3fa584d54a230
building syzkaller on bc2c6e45b9f01fa6046cb3efa9d3aae9f05238a8
testing commit ddef1e8e3f6eb26034833b7255e3fa584d54a230 with gcc (GCC) 8.1.0
kernel signature: e770ac9bad59b66e1de858f225a1dfe62c43bc9105f62f44473a638a1ea2a063
all runs: crashed: KASAN: use-after-free Read in debugfs_remove
testing current HEAD 12cd844a39ed16aa183a820a54fe6f9a0bb4cd14
testing commit 12cd844a39ed16aa183a820a54fe6f9a0bb4cd14 with gcc (GCC) 8.1.0
kernel signature: 0b43b6dc510722e153c1c5f2b7d85f888c8a6d1fe4e9398b4758a61a7210684f
all runs: crashed: KASAN: use-after-free Read in debugfs_remove
revisions tested: 2, total time: 39m25.578651756s (build: 18m5.837314778s, test: 20m23.049943902s)
the crash still happens on HEAD
commit msg: Linux 4.14.173
crash: KASAN: use-after-free Read in debugfs_remove
devpts: called with bogus options
devpts: called with bogus options
devpts: called with bogus options
devpts: called with bogus options
==================================================================
BUG: KASAN: use-after-free in debugfs_remove+0xda/0x100 fs/debugfs/inode.c:662
Read of size 8 at addr ffff8880a77bf300 by task kworker/1:4/10648

CPU: 1 PID: 10648 Comm: kworker/1:4 Not tainted 4.14.173-syzkaller #0
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:17 [inline]
 dump_stack+0xf7/0x13b lib/dump_stack.c:58
 print_address_description.cold.7+0x9/0x1c9 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.8+0x11a/0x2d3 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 debugfs_remove+0xda/0x100 fs/debugfs/inode.c:662
 blk_trace_free+0x30/0x130 kernel/trace/blktrace.c:324
 blk_trace_cleanup kernel/trace/blktrace.c:351 [inline]
 blk_trace_remove+0x42/0x70 kernel/trace/blktrace.c:364
 blk_trace_shutdown+0x42/0x50 kernel/trace/blktrace.c:728
 __blk_release_queue+0x1f9/0x470 block/blk-sysfs.c:830
 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2114
 worker_thread+0xcc/0xee0 kernel/workqueue.c:2248
 kthread+0x338/0x400 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 10654:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:551
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x790 mm/slab.c:3552
 __d_alloc+0x28/0x9f0 fs/dcache.c:1623
 d_alloc+0x43/0x260 fs/dcache.c:1710
 __lookup_hash+0x40/0x160 fs/namei.c:1571
 lookup_one_len+0x26e/0x3a0 fs/namei.c:2539
 start_creating+0x91/0x190 fs/debugfs/inode.c:314
 __debugfs_create_file+0x37/0x390 fs/debugfs/inode.c:353
 debugfs_create_file+0x24/0x30 fs/debugfs/inode.c:404
 do_blk_trace_setup+0x2fe/0xb10 kernel/trace/blktrace.c:529
 blk_trace_setup+0xa8/0x110 kernel/trace/blktrace.c:579
 blk_trace_ioctl+0x136/0x230 kernel/trace/blktrace.c:694
 blkdev_ioctl+0x6ae/0x16b0 block/ioctl.c:580
 block_ioctl+0xd7/0x130 fs/block_dev.c:1881
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x180/0xfb0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x74/0x80 fs/ioctl.c:692
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 17:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x80/0x2d0 mm/slab.c:3758
 __d_free+0x17/0x20 fs/dcache.c:270
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2699 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline]
 rcu_process_callbacks+0x7e0/0x11e0 kernel/rcu/tree.c:2946
 __do_softirq+0x246/0x9b0 kernel/softirq.c:288

The buggy address belongs to the object at ffff8880a77bf2c0
 which belongs to the cache dentry of size 288
The buggy address is located 64 bytes inside of
 288-byte region [ffff8880a77bf2c0, ffff8880a77bf3e0)
The buggy address belongs to the page:
page:ffffea00029defc0 count:1 mapcount:0 mapping:ffff8880a77bf000 index:0x0
flags: 0x1fffc0000000100(slab)
raw: 01fffc0000000100 ffff8880a77bf000 0000000000000000 000000010000000b
raw: ffffea00029deee0 ffffea0002263360 ffff88821f8b5680 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a77bf200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880a77bf280: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff8880a77bf300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff8880a77bf380: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff8880a77bf400: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================