Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in mgmt_remove_adv_monitor_sync

[syzbot]

Hello,

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

======================================================
WARNING: possible circular locking dependency detected
6.13.0-rc1-syzkaller-00025-gfeffde684ac2-dirty #0 Not tainted
------------------------------------------------------
syz.4.3898/15268 is trying to acquire lock:
ffff8880345205f0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
ffff8880345205f0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
ffff8880345205f0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4137 [inline]
ffff8880345205f0 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: __flush_work+0xe7/0xc50 kernel/workqueue.c:4195

but task is already holding lock:
ffff888034520078 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x5d4/0x11d0 net/bluetooth/hci_sync.c:5203

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&hdev->lock){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       hci_dev_close_sync+0x5d4/0x11d0 net/bluetooth/hci_sync.c:5203
       hci_dev_do_close net/bluetooth/hci_core.c:483 [inline]
       hci_unregister_dev+0x20b/0x510 net/bluetooth/hci_core.c:2698
       vhci_release+0x80/0xd0 drivers/bluetooth/hci_vhci.c:664
       __fput+0x23c/0xa50 fs/file_table.c:450
       task_work_run+0x24f/0x310 kernel/task_work.c:239
       exit_task_work include/linux/task_work.h:43 [inline]
       do_exit+0xa2f/0x28e0 kernel/exit.c:938
       do_group_exit+0x207/0x2c0 kernel/exit.c:1087
       get_signal+0x16b2/0x1750 kernel/signal.c:3017
       arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:337
       exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
       exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
       __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
       syscall_exit_to_user_mode+0xce/0x340 kernel/entry/common.c:218
       do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&hdev->req_lock){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x1ac/0xee0 kernel/locking/mutex.c:735
       hci_cmd_sync_work+0x1ec/0x400 net/bluetooth/hci_sync.c:331
       process_one_work kernel/workqueue.c:3229 [inline]
       process_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3310
       worker_thread+0x870/0xd30 kernel/workqueue.c:3391
       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:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
       touch_work_lockdep_map kernel/workqueue.c:3909 [inline]
       start_flush_work kernel/workqueue.c:4163 [inline]
       __flush_work+0x74e/0xc50 kernel/workqueue.c:4195
       __cancel_work_sync+0xbc/0x110 kernel/workqueue.c:4351
       hci_cmd_sync_clear+0x30/0x220 net/bluetooth/hci_sync.c:655
       hci_dev_close_sync+0x5dc/0x11d0 net/bluetooth/hci_sync.c:5204
       hci_dev_do_close net/bluetooth/hci_core.c:483 [inline]
       hci_dev_close+0x112/0x210 net/bluetooth/hci_core.c:508
       sock_do_ioctl+0x158/0x460 net/socket.c:1209
       sock_ioctl+0x626/0x8e0 net/socket.c:1328
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  (work_completion)(&hdev->cmd_sync_work) --> &hdev->req_lock --> &hdev->lock

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by syz.4.3898/15268:
 #0: ffff888034520d80 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close net/bluetooth/hci_core.c:481 [inline]
 #0: ffff888034520d80 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_close+0x10a/0x210 net/bluetooth/hci_core.c:508
 #1: ffff888034520078 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x5d4/0x11d0 net/bluetooth/hci_sync.c:5203
 #2: ffffffff8e937aa0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #2: ffffffff8e937aa0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #2: ffffffff8e937aa0 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4137 [inline]
 #2: ffffffff8e937aa0 (rcu_read_lock){....}-{1:3}, at: __flush_work+0xe7/0xc50 kernel/workqueue.c:4195

stack backtrace:
CPU: 1 UID: 0 PID: 15268 Comm: syz.4.3898 Not tainted 6.13.0-rc1-syzkaller-00025-gfeffde684ac2-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5226
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5849
 touch_work_lockdep_map kernel/workqueue.c:3909 [inline]
 start_flush_work kernel/workqueue.c:4163 [inline]
 __flush_work+0x74e/0xc50 kernel/workqueue.c:4195
 __cancel_work_sync+0xbc/0x110 kernel/workqueue.c:4351
 hci_cmd_sync_clear+0x30/0x220 net/bluetooth/hci_sync.c:655
 hci_dev_close_sync+0x5dc/0x11d0 net/bluetooth/hci_sync.c:5204
 hci_dev_do_close net/bluetooth/hci_core.c:483 [inline]
 hci_dev_close+0x112/0x210 net/bluetooth/hci_core.c:508
 sock_do_ioctl+0x158/0x460 net/socket.c:1209
 sock_ioctl+0x626/0x8e0 net/socket.c:1328
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xf5/0x170 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd2ecb80849
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd2eda59058 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd2ecd45fa0 RCX: 00007fd2ecb80849
RDX: 0000000000000000 RSI: 00000000400448ca RDI: 0000000000000004
RBP: 00007fd2ecbf3986 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fd2ecd45fa0 R15: 00007ffe9928ddb8
 </TASK>


Tested on:

commit:         feffde68 Merge tag 'for-6.13-rc1-tag' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10bf10f8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=50c7a61469ce77e7
dashboard link: https://syzkaller.appspot.com/bug?extid=479aff51bb361ef5aa18
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=162d2de8580000