bisecting fixing commit since a083db76118d20d070794ecf79af17843406c3f6
building syzkaller on 712198accc88c528b4460e661a93712ae53f16da
testing commit a083db76118d20d070794ecf79af17843406c3f6 with gcc (GCC) 8.1.0
kernel signature: bd77aeb98e462c52594c76c7920f0b02a58da72c6fc4accc1fd0f807e28062de
all runs: crashed: KASAN: use-after-free Read in debugfs_remove
testing current HEAD 258f0cf7ac3b788a14c0d01aab3c4aea02f8c86e
testing commit 258f0cf7ac3b788a14c0d01aab3c4aea02f8c86e with gcc (GCC) 8.1.0
kernel signature: a9f61e0bf95325fa8e359e06f47232bf14d8ba114aac88d35876a35469b4c132
all runs: crashed: KASAN: use-after-free Read in debugfs_remove
revisions tested: 2, total time: 30m52.048975231s (build: 20m50.803501734s, test: 8m12.665700702s)
the crash still happens on HEAD
commit msg: Linux 4.19.123
crash: KASAN: use-after-free Read in debugfs_remove
IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready
==================================================================
BUG: KASAN: use-after-free in debugfs_remove+0xd3/0xf0 fs/debugfs/inode.c:687
Read of size 8 at addr ffff888070ac1220 by task kworker/0:3/7764

CPU: 0 PID: 7764 Comm: kworker/0:3 Not tainted 4.19.123-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:77 [inline]
 dump_stack+0x123/0x177 lib/dump_stack.c:118
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 debugfs_remove+0xd3/0xf0 fs/debugfs/inode.c:687
 blk_trace_free+0x30/0x130 kernel/trace/blktrace.c:312
 blk_trace_cleanup kernel/trace/blktrace.c:340 [inline]
 __blk_trace_remove+0x5c/0x80 kernel/trace/blktrace.c:353
 blk_trace_shutdown+0x67/0xc0 kernel/trace/blktrace.c:755
 __blk_release_queue+0x1f7/0x490 block/blk-sysfs.c:855
 process_one_work+0x830/0x1670 kernel/workqueue.c:2155
 worker_thread+0x85/0xb60 kernel/workqueue.c:2298
 kthread+0x324/0x3e0 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 12746:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x730 mm/slab.c:3559
 __d_alloc+0x28/0x9d0 fs/dcache.c:1610
 d_alloc+0x42/0x220 fs/dcache.c:1694
 d_alloc_parallel+0xf3/0x1750 fs/dcache.c:2441
 __lookup_slow+0x18d/0x400 fs/namei.c:1655
 lookup_one_len+0x132/0x160 fs/namei.c:2544
 start_creating+0x91/0x190 fs/debugfs/inode.c:313
 __debugfs_create_file+0x37/0x390 fs/debugfs/inode.c:352
 debugfs_create_file+0x24/0x30 fs/debugfs/inode.c:404
 do_blk_trace_setup+0x31e/0xa70 kernel/trace/blktrace.c:529
 __blk_trace_setup+0xb4/0x130 kernel/trace/blktrace.c:578
 blk_trace_ioctl+0x151/0x270 kernel/trace/blktrace.c:719
 blkdev_ioctl+0x6d8/0x16e0 block/ioctl.c:587
 block_ioctl+0xd7/0x130 fs/block_dev.c:1894
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688
 ksys_ioctl+0x62/0x90 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 18:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kmem_cache_free+0x83/0x290 mm/slab.c:3765
 __d_free+0x17/0x20 fs/dcache.c:257
 __rcu_reclaim kernel/rcu/rcu.h:236 [inline]
 rcu_do_batch kernel/rcu/tree.c:2584 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2897 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2864 [inline]
 rcu_process_callbacks+0xbcd/0x19a0 kernel/rcu/tree.c:2881
 __do_softirq+0x260/0x92d kernel/softirq.c:292

The buggy address belongs to the object at ffff888070ac11e0
 which belongs to the cache dentry of size 288
The buggy address is located 64 bytes inside of
 288-byte region [ffff888070ac11e0, ffff888070ac1300)
The buggy address belongs to the page:
page:ffffea0001c2b040 count:1 mapcount:0 mapping:ffff8880aa4d86c0 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffffea0001c2a588 ffffea0001c2c188 ffff8880aa4d86c0
raw: 0000000000000000 ffff888070ac1080 000000010000000b 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888070ac1100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888070ac1180: fb fb fb fb fc fc fc fc fc fc fc fc fb fb fb fb
>ffff888070ac1200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888070ac1280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888070ac1300: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================