Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap_connect (2)

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in hci_dev_do_close

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc6-syzkaller-00326-gd1f2d51b711a-dirty #0 Not tainted
------------------------------------------------------
syz-executor/5776 is trying to acquire lock:
ffff88807d6ca148 ((wq_completion)hci1#2){+.+.}-{0:0}, at: touch_wq_lockdep_map+0x6e/0x120 kernel/workqueue.c:3875

but task is already holding lock:
ffff888060a68d80 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:481

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&hdev->req_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       hci_acldata_packet net/bluetooth/hci_core.c:3792 [inline]
       hci_rx_work+0xabf/0x1650 net/bluetooth/hci_core.c:4033
       process_one_work+0x9c5/0x1b40 kernel/workqueue.c:3231
       process_scheduled_works kernel/workqueue.c:3312 [inline]
       worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #1 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}:
       process_one_work+0x927/0x1b40 kernel/workqueue.c:3207
       process_scheduled_works kernel/workqueue.c:3312 [inline]
       worker_thread+0x6c8/0xed0 kernel/workqueue.c:3389
       kthread+0x2c1/0x3a0 kernel/kthread.c:389
       ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

-> #0 ((wq_completion)hci1#2){+.+.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3133 [inline]
       check_prevs_add kernel/locking/lockdep.c:3252 [inline]
       validate_chain kernel/locking/lockdep.c:3868 [inline]
       __lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
       lock_acquire kernel/locking/lockdep.c:5759 [inline]
       lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
       touch_wq_lockdep_map+0x78/0x120 kernel/workqueue.c:3875
       __flush_workqueue+0x129/0x1200 kernel/workqueue.c:3917
       drain_workqueue+0x18f/0x3d0 kernel/workqueue.c:4081
       hci_dev_close_sync+0x333/0x1110 net/bluetooth/hci_sync.c:5181
       hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:483
       hci_unregister_dev+0x213/0x620 net/bluetooth/hci_core.c:2698
       vhci_release+0x7f/0x100 drivers/bluetooth/hci_vhci.c:664
       __fput+0x408/0xbb0 fs/file_table.c:422
       task_work_run+0x14e/0x250 kernel/task_work.c:228
       exit_task_work include/linux/task_work.h:40 [inline]
       do_exit+0xaa3/0x2bb0 kernel/exit.c:882
       do_group_exit+0xd3/0x2a0 kernel/exit.c:1031
       get_signal+0x25fb/0x2770 kernel/signal.c:2917
       arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:310
       exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
       exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
       __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
       syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
       do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  (wq_completion)hci1#2 --> (work_completion)(&hdev->rx_work) --> &hdev->req_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&hdev->req_lock);
                               lock((work_completion)(&hdev->rx_work));
                               lock(&hdev->req_lock);
  lock((wq_completion)hci1#2);

 *** DEADLOCK ***

1 lock held by syz-executor/5776:
 #0: ffff888060a68d80 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:481

stack backtrace:
CPU: 0 UID: 0 PID: 5776 Comm: syz-executor Not tainted 6.11.0-rc6-syzkaller-00326-gd1f2d51b711a-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2186
 check_prev_add kernel/locking/lockdep.c:3133 [inline]
 check_prevs_add kernel/locking/lockdep.c:3252 [inline]
 validate_chain kernel/locking/lockdep.c:3868 [inline]
 __lock_acquire+0x24ed/0x3cb0 kernel/locking/lockdep.c:5142
 lock_acquire kernel/locking/lockdep.c:5759 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724
 touch_wq_lockdep_map+0x78/0x120 kernel/workqueue.c:3875
 __flush_workqueue+0x129/0x1200 kernel/workqueue.c:3917
 drain_workqueue+0x18f/0x3d0 kernel/workqueue.c:4081
 hci_dev_close_sync+0x333/0x1110 net/bluetooth/hci_sync.c:5181
 hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:483
 hci_unregister_dev+0x213/0x620 net/bluetooth/hci_core.c:2698
 vhci_release+0x7f/0x100 drivers/bluetooth/hci_vhci.c:664
 __fput+0x408/0xbb0 fs/file_table.c:422
 task_work_run+0x14e/0x250 kernel/task_work.c:228
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xaa3/0x2bb0 kernel/exit.c:882
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1031
 get_signal+0x25fb/0x2770 kernel/signal.c:2917
 arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x150/0x2a0 kernel/entry/common.c:218
 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc96277bb8a
Code: Unable to access opcode bytes at 0x7fc96277bb60.
RSP: 002b:00007ffc87843a70 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007fc96277bb8a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007ffc87843abc R08: 00007ffc878433cc R09: 00007ffc878437d7
R10: 00007ffc87843450 R11: 0000000000000293 R12: 0000000000000032
R13: 0000000000045913 R14: 00000000000458e1 R15: 00007ffc87843b10
 </TASK>


Tested on:

commit:         d1f2d51b Merge tag 'clk-fixes-for-linus' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14dd1f29980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=57042fe37c7ee7c2
dashboard link: https://syzkaller.appspot.com/bug?extid=c12e2f941af1feb5632c
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=10014877980000