BUG: unable to handle kernel NULL pointer dereference in hci_uart_set_flow_control

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 54c49016 Merge tag 'arc-5.1-rc2' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=150552df200000
kernel config: https://syzkaller.appspot.com/x/.config?x=9a31fb246de2a622
dashboard link: https://syzkaller.appspot.com/bug?extid=79337b501d6aa974d0f6
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15397fd7200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=151e9e6d200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+79337b...@syzkaller.appspotmail.com

BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
#PF error: [INSTR]
PGD a7d75067 P4D a7d75067 PUD 9fa83067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 1173 Comm: kworker/u5:0 Not tainted 5.1.0-rc1+ #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: hci0 hci_power_on
RIP: 0010: (null)
Code: Bad RIP value.
RSP: 0018:ffff8880a7807a28 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff87ac4d20 RCX: 0000000000000000
RDX: 1ffffffff0f589bd RSI: 1ffff11014fff58f RDI: ffff8880a0f6ca00
RBP: ffff8880a7807b00 R08: ffff8880a7ffa380 R09: 0000000000000004
R10: ffffed10141ed945 R11: ffff8880a0f6ca2f R12: ffff8880a0f6ca00
R13: 1ffff11014f00f47 R14: ffff8880a0f6ca10 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000009fa85000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
hci_uart_set_flow_control+0x41e/0x600 drivers/bluetooth/hci_ldisc.c:327
mrvl_setup+0x22/0x110 drivers/bluetooth/hci_mrvl.c:348
hci_uart_setup+0x1c4/0x490 drivers/bluetooth/hci_ldisc.c:418
hci_dev_do_open+0x78c/0x1780 net/bluetooth/hci_core.c:1450
hci_power_on+0x10d/0x580 net/bluetooth/hci_core.c:2173
process_one_work+0x98e/0x1790 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x357/0x430 kernel/kthread.c:253
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Modules linked in:
CR2: 0000000000000000
---[ end trace 1fd0bc84b188ab23 ]---
RIP: 0010: (null)
Code: Bad RIP value.
RSP: 0018:ffff8880a7807a28 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff87ac4d20 RCX: 0000000000000000
RDX: 1ffffffff0f589bd RSI: 1ffff11014fff58f RDI: ffff8880a0f6ca00
RBP: ffff8880a7807b00 R08: ffff8880a7ffa380 R09: 0000000000000004
R10: ffffed10141ed945 R11: ffff8880a0f6ca2f R12: ffff8880a0f6ca00
R13: 1ffff11014f00f47 R14: ffff8880a0f6ca10 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000009fa85000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot has bisected this bug to:

commit 162f812f23bab583f5d514ca0e4df67797ac9cdf
Author: Loic Poulain <loic.p...@intel.com>
Date: Mon Sep 19 14:29:27 2016 +0000

Bluetooth: hci_uart: Add Marvell support

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=112f0a3b200000
start commit: 162f812f Bluetooth: hci_uart: Add Marvell support
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=132f0a3b200000
console output: https://syzkaller.appspot.com/x/log.txt?x=152f0a3b200000

kernel config: https://syzkaller.appspot.com/x/.config?x=9a31fb246de2a622
dashboard link: https://syzkaller.appspot.com/bug?extid=79337b501d6aa974d0f6

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15397fd7200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=151e9e6d200000

Reported-by: syzbot+79337b...@syzkaller.appspotmail.com
Fixes: 162f812f23ba ("Bluetooth: hci_uart: Add Marvell support")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[vdr...@redhat.com]

the fix discussion: https://lore.kernel.org/lkml/20190625173215....@redhat.com/T/#u

going to post a v2 fix in a while.