linux-kernel - [Linux Kernel Warning] WARNING in rcu_pending_rcu

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Message-ID: <CANypQFbzds2uypT4Da89yc2YPSw0dzxbJ4yGY1ENrqj7Ys7LBw@mail.gmail.com>
Date: Fri, 22 Aug 2025 11:52:13 +0800
From: Jiaming Zhang <r772577952@...il.com>
To: kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org, tj@...nel.org, 
	jiangshanlai@...il.com, security@...nel.org
Cc: linux-kernel@...r.kernel.org, syzkaller@...glegroups.com
Subject: [Linux Kernel Warning] WARNING in rcu_pending_rcu_cb

Dear Linux kernel developers and maintainers:

We are writing to report a WARNING discovered in kernel/workqueue.c with a
modified syzkaller.

This bug was initially found in Linux kernel v6.7 (commit
0dd3ee31125508cd67f7e7172247f05b7fd1753a), and it is reproducible on the
latest version (v6.17-rc2, commit c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9).

The execution log, kernel config, syzkaller reproducer, and C reproducer
are attached to this email to help analysis. The bug report from v6.17-rc2,
formatted by syz-symbolize, is listed below.

==================================================================
WARNING: CPU: 0 PID: 4547 at kernel/workqueue.c:2323
__queue_work+0xd55/0xfb0 kernel/workqueue.c:2323
Modules linked in:
CPU: 0 UID: 0 PID: 4547 Comm: kworker/0:3 Not tainted 6.17.0-rc2 #1
PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1
04/01/2014
Workqueue: rcu_gp srcu_invoke_callbacks
RIP: 0010:__queue_work+0xd55/0xfb0 kernel/workqueue.c:2323
Code: 20 dd 49 8b 4c 89 fa e8 89 27 f9 ff 90 0f 0b 90 90 e9 1a f5 ff ff e8
5a 0d 36 00 90 0f 0b 90 e9 dd fc ff ff e8 4c 0d 36 00 90 <0f> 0b 90 e9 52
fe ff ff e8 3e 0d 36 00 90 0f 0b 90 e9 25 f3 ff ff
RSP: 0018:ffffc900022f77b0 EFLAGS: 00010093
RAX: ffffffff817febe4 RBX: 0000000000000001 RCX: ffff88801855dac0
RDX: 0000000000000000 RSI: ffffffff8ba27de0 RDI: ffffffff8ba27da0
RBP: 1ffff1100290f1b8 R08: ffffffff8f55a537 R09: 1ffffffff1eab4a6
R10: dffffc0000000000 R11: fffffbfff1eab4a7 R12: dffffc0000000000
R13: ffff88801488c000 R14: ffffe8ffad2297d0 R15: ffff888014878c00
FS:  0000000000000000(0000) GS:ffff88809a042000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000222e0d68 CR3: 000000004c282000 CR4: 0000000000752ef0
PKRU: 55555554
Call Trace:
 <TASK>
 queue_work_on+0x175/0x260 kernel/workqueue.c:2390
 schedule_work_on include/linux/workqueue.h:711 [inline]
 rcu_pending_rcu_cb+0x74/0x200 fs/bcachefs/rcu_pending.c:316
 srcu_invoke_callbacks+0x1f4/0x430 kernel/rcu/srcutree.c:1807
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3ea/0x760 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
==================================================================

Please let me know if any further information is required.

Best Regards,
Jiaming Zhang.

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