[syzbot] [bluetooth?] possible deadlock in hci_dev_do_close

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 940fcc189c51 Add linux-next specific files for 20230921
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=127d4f64680000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f140ae6e669ac24
dashboard link: https://syzkaller.appspot.com/bug?extid=4e3a76c5c505a3f49083
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1081124a680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10cfe14a680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b8921b235c24/disk-940fcc18.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c80a9f6bcdd4/vmlinux-940fcc18.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed10a4df6950/bzImage-940fcc18.xz

The issue was bisected to:

commit 091e25d6b54992d1d702ae91cbac139d4c243251
Author: Arkadiusz Bokowy <arkadius...@gmail.com>
Date: Wed Sep 20 15:30:07 2023 +0000

Bluetooth: vhci: Fix race when opening vhci device

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1326e53c680000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10a6e53c680000
console output: https://syzkaller.appspot.com/x/log.txt?x=1726e53c680000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e3a76...@syzkaller.appspotmail.com
Fixes: 091e25d6b549 ("Bluetooth: vhci: Fix race when opening vhci device")

======================================================
WARNING: possible circular locking dependency detected
6.6.0-rc2-next-20230921-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor126/5053 is trying to acquire lock:
ffff88807df1cdc0 ((work_completion)(&hdev->tx_work)){+.+.}-{0:0}, at: __flush_work+0xfa/0xa10 kernel/workqueue.c:3403

but task is already holding lock:
ffff88807df1d0b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:552

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&hdev->req_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:552
hci_rfkill_set_block+0x1b9/0x200 net/bluetooth/hci_core.c:956
rfkill_set_block+0x200/0x550 net/rfkill/core.c:346
rfkill_fop_write+0x2d4/0x570 net/rfkill/core.c:1306
vfs_write+0x2a4/0xe40 fs/read_write.c:582
ksys_write+0x1f0/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #2 (rfkill_global_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
rfkill_register+0x3a/0xb30 net/rfkill/core.c:1075
hci_register_dev+0x43a/0xd40 net/bluetooth/hci_core.c:2656
__vhci_create_device+0x393/0x800 drivers/bluetooth/hci_vhci.c:437
vhci_create_device drivers/bluetooth/hci_vhci.c:478 [inline]
vhci_get_user drivers/bluetooth/hci_vhci.c:535 [inline]
vhci_write+0x2c7/0x470 drivers/bluetooth/hci_vhci.c:615
call_write_iter include/linux/fs.h:1957 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x650/0xe40 fs/read_write.c:584
ksys_write+0x12f/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #1 (&data->open_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
vhci_send_frame+0x67/0xa0 drivers/bluetooth/hci_vhci.c:78
hci_send_frame+0x220/0x470 net/bluetooth/hci_core.c:3039
hci_sched_acl_pkt net/bluetooth/hci_core.c:3651 [inline]
hci_sched_acl net/bluetooth/hci_core.c:3736 [inline]
hci_tx_work+0x1456/0x1e40 net/bluetooth/hci_core.c:3835
process_one_work+0x884/0x15c0 kernel/workqueue.c:2630
process_scheduled_works kernel/workqueue.c:2703 [inline]
worker_thread+0x8b9/0x1290 kernel/workqueue.c:2784
kthread+0x33c/0x440 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

-> #0 ((work_completion)(&hdev->tx_work)){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
__flush_work+0x103/0xa10 kernel/workqueue.c:3403
hci_dev_close_sync+0x22d/0x1160 net/bluetooth/hci_sync.c:4982
hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:554
hci_rfkill_set_block+0x1b9/0x200 net/bluetooth/hci_core.c:956
rfkill_set_block+0x200/0x550 net/rfkill/core.c:346
rfkill_fop_write+0x2d4/0x570 net/rfkill/core.c:1306
vfs_write+0x2a4/0xe40 fs/read_write.c:582
ksys_write+0x1f0/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Chain exists of:
(work_completion)(&hdev->tx_work) --> rfkill_global_mutex --> &hdev->req_lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&hdev->req_lock);
lock(rfkill_global_mutex);
lock(&hdev->req_lock);
lock((work_completion)(&hdev->tx_work));

*** DEADLOCK ***

2 locks held by syz-executor126/5053:
#0: ffffffff8ea842a8 (rfkill_global_mutex){+.+.}-{3:3}, at: rfkill_fop_write+0x16e/0x570 net/rfkill/core.c:1298
#1: ffff88807df1d0b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:552

stack backtrace:
CPU: 1 PID: 5053 Comm: syz-executor126 Not tainted 6.6.0-rc2-next-20230921-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
check_noncircular+0x311/0x3f0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
__flush_work+0x103/0xa10 kernel/workqueue.c:3403
hci_dev_close_sync+0x22d/0x1160 net/bluetooth/hci_sync.c:4982
hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:554
hci_rfkill_set_block+0x1b9/0x200 net/bluetooth/hci_core.c:956
rfkill_set_block+0x200/0x550 net/rfkill/core.c:346
rfkill_fop_write+0x2d4/0x570 net/rfkill/core.c:1306
vfs_write+0x2a4/0xe40 fs/read_write.c:582
ksys_write+0x1f0/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f8297388479
Code: 48 83 c4 28 c3 e8 e7 18 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc9ef0d068 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f82973df043 RCX: 00007f8297388479
RDX: 0000000000000008 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00007ffc9ef0d0b0 R08: 000000ff00ffa650 R09: 000000ff00ffa650
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc9ef0d098
R13: 00007f829740c5b0 R14: 0000000000000000 R15: 0000000000000001
</TASK>


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

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite bug's subsystems, reply with:
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If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Hillf Danton]

On Sun, 24 Sep 2023 22:15:39 -0700

> HEAD commit: 940fcc189c51 Add linux-next specific files for 20230921
> git tree: linux-next

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10cfe14a680000


#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 940fcc189c51

--- x/drivers/bluetooth/hci_vhci.c
+++ y/drivers/bluetooth/hci_vhci.c
@@ -75,9 +75,7 @@ static int vhci_send_frame(struct hci_de

memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1);

- mutex_lock(&data->open_mutex);
skb_queue_tail(&data->readq, skb);
- mutex_unlock(&data->open_mutex);

wake_up_interruptible(&data->read_wait);
return 0;
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+4e3a76...@syzkaller.appspotmail.com

Tested on:

commit: 940fcc18 Add linux-next specific files for 20230921
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=17524612680000

kernel config: https://syzkaller.appspot.com/x/.config?x=1f140ae6e669ac24
dashboard link: https://syzkaller.appspot.com/bug?extid=4e3a76c5c505a3f49083
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=11c855c1680000

Note: testing is done by a robot and is best-effort only.

[Fedor Pchelkin]

#syz dup: possible deadlock in hci_rfkill_set_block