------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: lib/refcount.c:25 at refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25, CPU#0: syz.0.0/5334
Modules linked in:
CPU: 0 UID: 0 PID: 5334 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:refcount_warn_saturate+0x9f/0x110 lib/refcount.c:25
Code: eb 66 85 db 74 3e 83 fb 01 75 4c e8 2b 0d f2 fc 48 8d 3d 24 07 8e 0b 67 48 0f b9 3a eb 4a e8 18 0d f2 fc 48 8d 3d 21 07 8e 0b <67> 48 0f b9 3a eb 37 e8 05 0d f2 fc 48 8d 3d 1e 07 8e 0b 67 48 0f
RSP: 0018:ffffc9000f1e7c48 EFLAGS: 00010293
RAX: ffffffff84d515c8 RBX: 0000000000000002 RCX: ffff88803ebb0000
RDX: 0000000000000000 RSI: ffffffff8f367700 RDI: ffffffff90631cf0
RBP: 0000000000000000 R08: ffff88803ebb0000 R09: 0000000000000005
R10: 0000000000000004 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff888000e46530 R14: ffff88801fa0a01c R15: 1ffff92001e3cfa0
FS:  00007f44560a16c0(0000) GS:ffff88808c540000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffdc826da80 CR3: 0000000012150000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 __refcount_add include/linux/refcount.h:-1 [inline]
 __refcount_inc include/linux/refcount.h:366 [inline]
 refcount_inc include/linux/refcount.h:383 [inline]
 kref_get include/linux/kref.h:45 [inline]
 config_item_get+0x88/0x90 fs/configfs/item.c:104
 configfs_get_config_item fs/configfs/configfs_internal.h:127 [inline]
 get_target fs/configfs/symlink.c:128 [inline]
 configfs_symlink+0x4ab/0x1030 fs/configfs/symlink.c:185
 vfs_symlink+0x18b/0x330 fs/namei.c:5660
 filename_symlinkat+0x1cd/0x410 fs/namei.c:5685
 __do_sys_symlinkat fs/namei.c:5705 [inline]
 __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5700
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f445519e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f44560a0fe8 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f4455425fa0 RCX: 00007f445519e0d9
RDX: 00002000000002c0 RSI: ffffffffffffff9c RDI: 0000200000000280
RBP: 00007f4455235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4455426038 R14: 00007f4455425fa0 R15: 00007ffdc826e268
 </TASK>
----------------
Code disassembly (best guess):
   0:	eb 66                	jmp    0x68
   2:	85 db                	test   %ebx,%ebx
   4:	74 3e                	je     0x44
   6:	83 fb 01             	cmp    $0x1,%ebx
   9:	75 4c                	jne    0x57
   b:	e8 2b 0d f2 fc       	call   0xfcf20d3b
  10:	48 8d 3d 24 07 8e 0b 	lea    0xb8e0724(%rip),%rdi        # 0xb8e073b
  17:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  1c:	eb 4a                	jmp    0x68
  1e:	e8 18 0d f2 fc       	call   0xfcf20d3b
  23:	48 8d 3d 21 07 8e 0b 	lea    0xb8e0721(%rip),%rdi        # 0xb8e074b
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	eb 37                	jmp    0x68
  31:	e8 05 0d f2 fc       	call   0xfcf20d3b
  36:	48 8d 3d 1e 07 8e 0b 	lea    0xb8e071e(%rip),%rdi        # 0xb8e075b
  3d:	67                   	addr32
  3e:	48                   	rex.W
  3f:	0f                   	.byte 0xf