general protection fault in debugfs_remove

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    dc4060a5 Linux 5.1-rc5
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146c7ab7200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=856fc6d0fbbeede9
dashboard link: https://syzkaller.appspot.com/bug?extid=c091783d82e47615bb28
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+c091783d82e47615bb28@xxxxxxxxxxxxxxxxxxxxxxxxx

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 17253 Comm: syz-executor.2 Not tainted 5.1.0-rc5 #68
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:__lock_acquire+0xbef/0x3fb0 kernel/locking/lockdep.c:3573
Code: 00 0f 85 a5 1f 00 00 48 81 c4 10 01 00 00 5b 41 5c 41 5d 41 5e 41 5f  
5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f  
85 4a 21 00 00 49 81 7d 00 20 54 9c 89 0f 84 cf f4
RSP: 0018:ffff88805c8c7af0 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000027 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffff88805c8c7c28 R08: 0000000000000001 R09: 0000000000000000
R10: ffffed100bd89a87 R11: ffff8880a447e640 R12: 0000000000000000
R13: 0000000000000138 R14: 0000000000000000 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880ae900000(0063) knlGS:00000000f5d5bb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007fa5913df4a0 CR3: 0000000098cec000 CR4: 00000000001426e0
Call Trace:
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4211
 down_write+0x38/0x90 kernel/locking/rwsem.c:70
 inode_lock include/linux/fs.h:772 [inline]
 debugfs_remove+0x94/0x130 fs/debugfs/inode.c:691
 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:731
 compat_blkdev_ioctl+0x461/0x1a60 block/compat_ioctl.c:402
 __do_compat_sys_ioctl fs/compat_ioctl.c:1052 [inline]
 __se_compat_sys_ioctl fs/compat_ioctl.c:998 [inline]
 __ia32_compat_sys_ioctl+0x197/0x620 fs/compat_ioctl.c:998
 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
 do_fast_syscall_32+0x281/0xc98 arch/x86/entry/common.c:397
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f5f869
Code: 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 14 24 c3 8b 3c 24 c3 90 90  
90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90  
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f5d5b0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000001276
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 91aa7acaf1536f2c ]---
RIP: 0010:__lock_acquire+0xbef/0x3fb0 kernel/locking/lockdep.c:3573
Code: 00 0f 85 a5 1f 00 00 48 81 c4 10 01 00 00 5b 41 5c 41 5d 41 5e 41 5f  
5d c3 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f  
85 4a 21 00 00 49 81 7d 00 20 54 9c 89 0f 84 cf f4
RSP: 0018:ffff88805c8c7af0 EFLAGS: 00010006
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000027 RSI: 0000000000000000 RDI: 0000000000000001
RBP: ffff88805c8c7c28 R08: 0000000000000001 R09: 0000000000000000
R10: ffffed100bd89a87 R11: ffff8880a447e640 R12: 0000000000000000
R13: 0000000000000138 R14: 0000000000000000 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff8880ae900000(0063) knlGS:00000000f5d5bb40
CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: 00007fa5913df4a0 CR3: 0000000098cec000 CR4: 00000000001426e0


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