general protection fault in rfcomm_dlc_exists

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    26f146ed net: ll_temac: Fix typo bug for 32-bit
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1481e350a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=70f5b9827d8c73d8
dashboard link: https://syzkaller.appspot.com/bug?extid=362be51217ce29d215bc
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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+362be51217ce29d215bc@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: 0 PID: 29087 Comm: syz-executor.2 Not tainted 5.1.0-rc6+ #164
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:rfcomm_dlc_get net/bluetooth/rfcomm/core.c:360 [inline]
RIP: 0010:rfcomm_dlc_exists+0x12e/0x1a0 net/bluetooth/rfcomm/core.c:550
Code: 42 80 3c 28 00 75 74 4d 8b 24 24 4d 39 f4 74 55 e8 37 99 16 fb 49 8d  
bc 24 44 01 00 00 48 89 f8 48 89 fa 48 c1 e8 03 83 e2 07 <42> 0f b6 04 28  
38 d0 7f 04 84 c0 75 3d 45 0f b6 bc 24 44 01 00 00
RSP: 0018:ffff88809e9f79c0 EFLAGS: 00010202
RAX: 0ecc2d8e6bee4e95 RBX: 000000000000000d RCX: ffffc90005ffc000
RDX: 0000000000000004 RSI: ffffffff8659f3e9 RDI: 76616c735f7274ac
RBP: ffff88809e9f79e8 R08: ffff888093d44580 R09: fffffbfff1289895
R10: ffff88809e9f79b0 R11: ffffffff8944c4a7 R12: 76616c735f727368
R13: dffffc0000000000 R14: ffff88809b2d3980 R15: 0000000000000000
FS:  00007faf4b6fc700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f90c3150000 CR3: 0000000097c73000 CR4: 00000000001406f0
Call Trace:
 __rfcomm_create_dev net/bluetooth/rfcomm/tty.c:413 [inline]
 rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
 rfcomm_dev_ioctl+0x591/0x1b60 net/bluetooth/rfcomm/tty.c:588
 rfcomm_sock_ioctl+0x90/0xb0 net/bluetooth/rfcomm/sock.c:902
 sock_do_ioctl+0xde/0x300 net/socket.c:1037
 sock_ioctl+0x3f3/0x790 net/socket.c:1188
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd6e/0x1390 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458da9
Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007faf4b6fbc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458da9
RDX: 0000000020000100 RSI: 00000000400452c8 RDI: 0000000000000004
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007faf4b6fc6d4
R13: 00000000004c133a R14: 00000000004d3920 R15: 00000000ffffffff
Modules linked in:
---[ end trace 6a47bc10d7ab5e63 ]---
RIP: 0010:rfcomm_dlc_get net/bluetooth/rfcomm/core.c:360 [inline]
RIP: 0010:rfcomm_dlc_exists+0x12e/0x1a0 net/bluetooth/rfcomm/core.c:550
Code: 42 80 3c 28 00 75 74 4d 8b 24 24 4d 39 f4 74 55 e8 37 99 16 fb 49 8d  
bc 24 44 01 00 00 48 89 f8 48 89 fa 48 c1 e8 03 83 e2 07 <42> 0f b6 04 28  
38 d0 7f 04 84 c0 75 3d 45 0f b6 bc 24 44 01 00 00
RSP: 0018:ffff88809e9f79c0 EFLAGS: 00010202
RAX: 0ecc2d8e6bee4e95 RBX: 000000000000000d RCX: ffffc90005ffc000
RDX: 0000000000000004 RSI: ffffffff8659f3e9 RDI: 76616c735f7274ac
RBP: ffff88809e9f79e8 R08: ffff888093d44580 R09: fffffbfff1289895
R10: ffff88809e9f79b0 R11: ffffffff8944c4a7 R12: 76616c735f727368
R13: dffffc0000000000 R14: ffff88809b2d3980 R15: 0000000000000000
FS:  00007faf4b6fc700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000097c73000 CR4: 00000000001406f0


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