Re: WARNING: ODEBUG bug in rfcomm_dlc_free

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    116b181bb646 Add linux-next specific files for 20180803
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1010268c400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b4f38be7c2c519d5
dashboard link: https://syzkaller.appspot.com/bug?extid=1f6d4ad860c650c2f215
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=101200e2400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=121d3bdc400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+1f6d4ad860c650c2f215@xxxxxxxxxxxxxxxxxxxxxxxxx

random: sshd: uninitialized urandom read (32 bytes read)
urandom_read: 1 callbacks suppressed
random: sshd: uninitialized urandom read (32 bytes read)
------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: timer_list hint:  
rfcomm_dlc_timeout+0x0/0x70 include/linux/list.h:64
WARNING: CPU: 0 PID: 4267 at lib/debugobjects.c:329  
debug_print_object+0x16a/0x210 lib/debugobjects.c:326
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4267 Comm: syz-executor929 Not tainted  
4.18.0-rc7-next-20180803+ #31
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+0x1c9/0x2b4 lib/dump_stack.c:113
 panic+0x238/0x4e7 kernel/panic.c:184
 __warn.cold.8+0x163/0x1ba kernel/panic.c:536
 report_bug+0x252/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:996
RIP: 0010:debug_print_object+0x16a/0x210 lib/debugobjects.c:326
Code: 3a 87 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 92 00 00 00 48 8b 14 dd  
60 a8 3a 87 4c 89 f6 48 c7 c7 00 9e 3a 87 e8 26 70 e2 fd <0f> 0b 83 05 09  
33 26 05 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffff8801b686f648 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff816366f1 RDI: 0000000000000001
RBP: ffff8801b686f688 R08: ffff8801cb852380 R09: ffffed003b603ec2
R10: ffffed003b603ec2 R11: ffff8801db01f617 R12: 0000000000000001
R13: ffffffff87f9d1c0 R14: ffffffff873aa2a0 R15: ffffffff816988b0
 __debug_check_no_obj_freed lib/debugobjects.c:786 [inline]
 debug_check_no_obj_freed+0x3b2/0x595 lib/debugobjects.c:818
 kfree+0xc7/0x260 mm/slab.c:3812
 rfcomm_dlc_free+0x1e/0x30 net/bluetooth/rfcomm/core.c:328
 rfcomm_dlc_put include/net/bluetooth/rfcomm.h:258 [inline]
 __rfcomm_create_dev net/bluetooth/rfcomm/tty.c:417 [inline]
 rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
 rfcomm_dev_ioctl+0x1dfe/0x2240 net/bluetooth/rfcomm/tty.c:588
 rfcomm_sock_ioctl+0x89/0xb0 net/bluetooth/rfcomm/sock.c:902
 sock_do_ioctl+0xe4/0x3e0 net/socket.c:950
 sock_ioctl+0x30d/0x680 net/socket.c:1074
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4406d9
Code: e8 2c af 02 00 48 83 c4 18 c3 0f 1f 80 00 00 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 0f 83 3b 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff697e60e8 EFLAGS: 00000213 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004406d9
RDX: 0000000020000000 RSI: 00000000400452c8 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000013d1880 R11: 0000000000000213 R12: 0000000000009731
R13: 0000000000401c30 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..