linux-kernel - Re: [syzbot] [usb?] possible deadlock in chaoskey

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Message-ID: <6706468a.050a0220.22840d.0011.GAE@google.com>
Date: Wed, 09 Oct 2024 02:02:02 -0700
From: syzbot <syzbot+5f1ce62e956b7b19610e@...kaller.appspotmail.com>
To: eadavis@...com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [usb?] possible deadlock in chaoskey_open

Hello,

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

============================================
WARNING: possible recursive locking detected
6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53-dirty #0 Not tainted
--------------------------------------------
syz.1.16/6532 is trying to acquire lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x15d/0x2c0 drivers/usb/misc/chaoskey.c:322

but task is already holding lock:
ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x7f/0x2c0 drivers/usb/misc/chaoskey.c:299

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(chaoskey_list_lock);
  lock(chaoskey_list_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

1 lock held by syz.1.16/6532:
 #0: ffffffff89b120e8 (chaoskey_list_lock){+.+.}-{3:3}, at: chaoskey_release+0x7f/0x2c0 drivers/usb/misc/chaoskey.c:299

stack backtrace:
CPU: 1 UID: 0 PID: 6532 Comm: syz.1.16 Not tainted 6.12.0-rc1-syzkaller-00027-g4a9fe2a8ac53-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+0x116/0x1f0 lib/dump_stack.c:120
 print_deadlock_bug+0x2e3/0x410 kernel/locking/lockdep.c:3037
 check_deadlock kernel/locking/lockdep.c:3089 [inline]
 validate_chain kernel/locking/lockdep.c:3891 [inline]
 __lock_acquire+0x2185/0x3ce0 kernel/locking/lockdep.c:5202
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752
 chaoskey_release+0x15d/0x2c0 drivers/usb/misc/chaoskey.c:322
 __fput+0x3f6/0xb60 fs/file_table.c:431
 task_work_run+0x14e/0x250 kernel/task_work.c:228
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [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+0x24e/0x260 kernel/entry/common.c:218
 do_syscall_64+0xda/0x250 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f35b167dff9
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:00007ffe690a74c8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 000000000001c363 RCX: 00007f35b167dff9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f35b1837a80 R08: 0000000000000001 R09: 00007ffe690a77bf
R10: 00007f35b14fa000 R11: 0000000000000246 R12: 000000000001cf4f
R13: 00007ffe690a75d0 R14: 0000000000000bea R15: ffffffffffffffff
 </TASK>


Tested on:

commit:         4a9fe2a8 dt-bindings: usb: dwc3-imx8mp: add compatible..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=15b89f9f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4510af5d637450fb
dashboard link: https://syzkaller.appspot.com/bug?extid=5f1ce62e956b7b19610e
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=14adf707980000