linux-kernel - [BUG] rcu_preempt stall detected by syzkaller on Linux v6.18

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Message-ID: <6ee827b.9258.19b86eefb7e.Coremail.23009200614@stu.xidian.edu.cn>
Date: Sun, 4 Jan 2026 10:56:07 +0800 (GMT+08:00)
From: 王志 <23009200614@....xidian.edu.cn>
To: paulmck@...nel.org
Cc: linux-rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzkaller@...glegroups.com
Subject: [BUG] rcu_preempt stall detected by syzkaller on Linux v6.18

Hello RCU maintainers,

This is a kernel bug found by syzkaller while fuzzing the upstream Linux kernel v6.18.

The kernel reports an RCU preempt stall, where the RCU grace-period kthread appears to be starved for a long time. After the stall, the system becomes largely unresponsive and may eventually hit OOM.

Kernel version:
  Linux v6.18
  Source: https://github.com/torvalds/linux/tree/v6.18
The issue was triggered by syz-executor. The relevant kernel log is shown below.
============================================================

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu:     (detected by 3, t=105004 jiffies, g=328445, q=426 ncpus=4)
rcu: rcu_preempt kthread starved for 105017 jiffies!
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
RCU grace-period kthread stack dump:
Call Trace:
 rcu_gp_fqs_loop+0x195/0x780 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x1da/0x270 kernel/rcu/tree.c:2285
 kthread+0x27c/0x430 kernel/kthread.c:463
 ret_from_fork+0x2a5/0x370 arch/x86/kernel/process.c:158

============================================================

Unfortunately, I do not yet have a minimal reproducer, but I can provide additional logs or testing if needed.

Please let me know if more information is required.

Best regards,
Zhi Wang