linux-kernel - Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in l2cap

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Message-ID: <0000000000005514e806219267eb@google.com>
Date: Sat, 07 Sep 2024 19:29:02 -0700
From: syzbot <syzbot+c12e2f941af1feb5632c@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bluetooth?] KASAN: slab-use-after-free Read in
 l2cap_connect (2)

Hello,

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

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc6-syzkaller-00326-gd1f2d51b711a-dirty #0 Not tainted
------------------------------------------------------
kworker/u9:2/5285 is trying to acquire lock:
ffff888043094aa0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: touch_work_lockdep_map kernel/workqueue.c:3890 [inline]
ffff888043094aa0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: start_flush_work kernel/workqueue.c:4144 [inline]
ffff888043094aa0 ((work_completion)(&hdev->rx_work)){+.+.}-{0:0}, at: __flush_work+0x46d/0xc30 kernel/workqueue.c:4176

but task is already holding lock:
ffff888043094078 (&hdev->lock){+.+.}-{3:3}, at: hci_abort_conn_sync+0x150/0xb50 net/bluetooth/hci_sync.c:5564

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&hdev->lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
       hci_store_wake_reason net/bluetooth/hci_event.c:7191 [inline]
       hci_event_packet+0x323/0x1180 net/bluetooth/hci_event.c:7494
       hci_rx_work+0x2c6/0x1610 net/bluetooth/hci_core.c:4023
       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

-> #0 ((work_completion)(&hdev->rx_work)){+.+.}-{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_work_lockdep_map kernel/workqueue.c:3890 [inline]
       start_flush_work kernel/workqueue.c:4144 [inline]
       __flush_work+0x477/0xc30 kernel/workqueue.c:4176
       __cancel_work_sync+0x10c/0x130 kernel/workqueue.c:4332
       hci_abort_conn_sync+0x75a/0xb50 net/bluetooth/hci_sync.c:5583
       abort_conn_sync+0x197/0x360 net/bluetooth/hci_conn.c:2918
       hci_cmd_sync_work+0x1a4/0x410 net/bluetooth/hci_sync.c:328
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&hdev->lock);
                               lock((work_completion)(&hdev->rx_work));
                               lock(&hdev->lock);
  lock((work_completion)(&hdev->rx_work));

 *** DEADLOCK ***

5 locks held by kworker/u9:2/5285:
 #0: ffff8880439ca148 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x1277/0x1b40 kernel/workqueue.c:3206
 #1: ffffc9000392fd80 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1b40 kernel/workqueue.c:3207
 #2: ffff888043094d80 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x170/0x410 net/bluetooth/hci_sync.c:327
 #3: ffff888043094078 (&hdev->lock){+.+.}-{3:3}, at: hci_abort_conn_sync+0x150/0xb50 net/bluetooth/hci_sync.c:5564
 #4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
 #4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: start_flush_work kernel/workqueue.c:4118 [inline]
 #4: ffffffff8ddb9fe0 (rcu_read_lock){....}-{1:2}, at: __flush_work+0x103/0xc30 kernel/workqueue.c:4176

stack backtrace:
CPU: 0 UID: 0 PID: 5285 Comm: kworker/u9:2 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
Workqueue: hci0 hci_cmd_sync_work
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_work_lockdep_map kernel/workqueue.c:3890 [inline]
 start_flush_work kernel/workqueue.c:4144 [inline]
 __flush_work+0x477/0xc30 kernel/workqueue.c:4176
 __cancel_work_sync+0x10c/0x130 kernel/workqueue.c:4332
 hci_abort_conn_sync+0x75a/0xb50 net/bluetooth/hci_sync.c:5583
 abort_conn_sync+0x197/0x360 net/bluetooth/hci_conn.c:2918
 hci_cmd_sync_work+0x1a4/0x410 net/bluetooth/hci_sync.c:328
 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
 </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=146feffb980000
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=175c0e00580000