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Date: Sun, 28 Apr 2024 15:35:27 -0700
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Subject: Re: [syzbot] [bluetooth?] possible deadlock in hci_dev_do_close (2)
From: syzbot <syzbot+c55f7bc8d4809b2bad59@syzkaller.appspotmail.com>
To: johan.hedberg@gmail.com, linux-bluetooth@vger.kernel.org, 
	linux-kernel@vger.kernel.org, luiz.dentz@gmail.com, marcel@holtmann.org, 
	syzkaller-bugs@googlegroups.com
Content-Type: text/plain; charset="UTF-8"

syzbot has found a reproducer for the following issue on:

HEAD commit:    bb7a2467e6be Add linux-next specific files for 20240426
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=16b60228980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6a0288262dd108
dashboard link: https://syzkaller.appspot.com/bug?extid=c55f7bc8d4809b2bad59
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1590bcf8980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1349ee9b180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5175af7dda64/disk-bb7a2467.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70db0462e868/vmlinux-bb7a2467.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3217fb825698/bzImage-bb7a2467.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c55f7bc8d4809b2bad59@syzkaller.appspotmail.com

Bluetooth: hci0: Opcode 0x0c1a failed: -110
Bluetooth: hci0: Error when powering off device on rfkill (-110)
======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc5-next-20240426-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor143/5093 is trying to acquire lock:
ffff88807643c8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
ffff88807643c8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
ffff88807643c8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4113 [inline]
ffff88807643c8d0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: __flush_work+0xe6/0xd00 kernel/workqueue.c:4172

but task is already holding lock:
ffff88807643d060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x28/0x90 net/bluetooth/hci_core.c:559

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&hdev->req_lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       hci_cmd_sync_work+0x1ec/0x400 net/bluetooth/hci_sync.c:309
       process_one_work kernel/workqueue.c:3222 [inline]
       process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3303
       worker_thread+0x86d/0xd70 kernel/workqueue.c:3384
       kthread+0x2f0/0x390 kernel/kthread.c:389
       ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       touch_work_lockdep_map kernel/workqueue.c:3885 [inline]
       start_flush_work kernel/workqueue.c:4139 [inline]
       __flush_work+0x73c/0xd00 kernel/workqueue.c:4172
       __cancel_work_sync+0xbc/0x110 kernel/workqueue.c:4322
       hci_cmd_sync_clear+0x30/0x220 net/bluetooth/hci_sync.c:588
       hci_dev_close_sync+0xbae/0x1060 net/bluetooth/hci_sync.c:5188
       hci_dev_do_close+0x30/0x90 net/bluetooth/hci_core.c:561
       hci_rfkill_set_block+0x232/0x300 net/bluetooth/hci_core.c:992
       rfkill_set_block+0x1f1/0x440 net/rfkill/core.c:346
       rfkill_fop_write+0x5bb/0x790 net/rfkill/core.c:1305
       do_loop_readv_writev fs/read_write.c:764 [inline]
       vfs_writev+0x733/0xbe0 fs/read_write.c:973
       do_writev+0x1b1/0x350 fs/read_write.c:1018
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by syz-executor143/5093:
 #0: ffffffff8f8b13e8 (rfkill_global_mutex){+.+.}-{3:3}, at: rfkill_fop_write+0x1a9/0x790 net/rfkill/core.c:1297
 #1: ffff88807643d060 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x28/0x90 net/bluetooth/hci_core.c:559
 #2: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #2: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #2: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: start_flush_work kernel/workqueue.c:4113 [inline]
 #2: ffffffff8e333ba0 (rcu_read_lock){....}-{1:2}, at: __flush_work+0xe6/0xd00 kernel/workqueue.c:4172

stack backtrace:
CPU: 0 PID: 5093 Comm: syz-executor143 Not tainted 6.9.0-rc5-next-20240426-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_noncircular+0x36a/0x4a0 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+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
 touch_work_lockdep_map kernel/workqueue.c:3885 [inline]
 start_flush_work kernel/workqueue.c:4139 [inline]
 __flush_work+0x73c/0xd00 kernel/workqueue.c:4172
 __cancel_work_sync+0xbc/0x110 kernel/workqueue.c:4322
 hci_cmd_sync_clear+0x30/0x220 net/bluetooth/hci_sync.c:588
 hci_dev_close_sync+0xbae/0x1060 net/bluetooth/hci_sync.c:5188
 hci_dev_do_close+0x30/0x90 net/bluetooth/hci_core.c:561
 hci_rfkill_set_block+0x232/0x300 net/bluetooth/hci_core.c:992
 rfkill_set_block+0x1f1/0x440 net/rfkill/core.c:346
 rfkill_fop_write+0x5bb/0x790 net/rfkill/core.c:1305
 do_loop_readv_writev fs/read_write.c:764 [inline]
 vfs_writev+0x733/0xbe0 fs/read_write.c:973
 do_writev+0x1b1/0x350 fs/read_write.c:1018
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f22b080b5d9
Code: 48 83 c4 28 c3 e8 47 1d 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:00007fff7aee1ff8 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f22b085b468 RCX: 00007f22b080b5d9
RDX: 0000000000000001 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00007fff7aee20f0 R08: 00007f2200000001 R09: 00007f2200000001
R10: 00007f2200000001 R11: 0000000000000246 R12: 0000000000000003
R13: 00007fff7aee20c0 R14: 0000000000000001 R15: 00007fff7aee20f0
 </TASK>


---
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