[syzbot] [crypto?] possible deadlock in padata_do_serial

[syzbot <syzbot+bd936ccd4339cea66e6b@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    2ae2aaafb214 Add linux-next specific files for 20250624
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10deb70c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d85d3c440a754f86
dashboard link: https://syzkaller.appspot.com/bug?extid=bd936ccd4339cea66e6b
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/689f558e5251/disk-2ae2aaaf.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/355aae0f4972/vmlinux-2ae2aaaf.xz
kernel image: https://storage.googleapis.com/syzbot-assets/94e736ebe604/bzImage-2ae2aaaf.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bd936ccd4339cea66e6b@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
6.16.0-rc3-next-20250624-syzkaller #0 Not tainted
--------------------------------------------
kworker/u8:11/20346 is trying to acquire lock:
ffffe8ffffd55fd8 (&pd_list->lock){+...}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffffe8ffffd55fd8 (&pd_list->lock){+...}-{3:3}, at: padata_find_next kernel/padata.c:256 [inline]
ffffe8ffffd55fd8 (&pd_list->lock){+...}-{3:3}, at: padata_reorder kernel/padata.c:309 [inline]
ffffe8ffffd55fd8 (&pd_list->lock){+...}-{3:3}, at: padata_do_serial+0x73e/0xb80 kernel/padata.c:379

but task is already holding lock:
ffffe8ffffd5f4d8 (&pd_list->lock){+...}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffffe8ffffd5f4d8 (&pd_list->lock){+...}-{3:3}, at: padata_reorder kernel/padata.c:300 [inline]
ffffe8ffffd5f4d8 (&pd_list->lock){+...}-{3:3}, at: padata_do_serial+0x5b5/0xb80 kernel/padata.c:379

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

       CPU0
       ----
  lock(&pd_list->lock);
  lock(&pd_list->lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by kworker/u8:11/20346:
 #0: ffff888146e84948 ((wq_completion)pencrypt_parallel){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
 #0: ffff888146e84948 ((wq_completion)pencrypt_parallel){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3322
 #1: ffffc9000bf7fbc0 ((work_completion)(&pw->pw_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3215 [inline]
 #1: ffffc9000bf7fbc0 ((work_completion)(&pw->pw_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3322
 #2: ffffe8ffffd5f4d8 (&pd_list->lock){+...}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline]
 #2: ffffe8ffffd5f4d8 (&pd_list->lock){+...}-{3:3}, at: padata_reorder kernel/padata.c:300 [inline]
 #2: ffffe8ffffd5f4d8 (&pd_list->lock){+...}-{3:3}, at: padata_do_serial+0x5b5/0xb80 kernel/padata.c:379

stack backtrace:
CPU: 1 UID: 0 PID: 20346 Comm: kworker/u8:11 Not tainted 6.16.0-rc3-next-20250624-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: pencrypt_parallel padata_parallel_worker
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3044
 check_deadlock kernel/locking/lockdep.c:3096 [inline]
 validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3898
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:351 [inline]
 padata_find_next kernel/padata.c:256 [inline]
 padata_reorder kernel/padata.c:309 [inline]
 padata_do_serial+0x73e/0xb80 kernel/padata.c:379
 padata_parallel_worker+0x75/0x1d0 kernel/padata.c:157
 process_one_work kernel/workqueue.c:3239 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3322
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3403
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


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