linux-kernel - Re: [PATCH] workqueue: Fix rescuer task's name truncated

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Message-ID: <f37cd607-cdde-4302-9515-7af2f958e841@huawei.com>
Date: Mon, 13 May 2024 21:28:10 +0800
From: Wenchao Hao <haowenchao2@...wei.com>
To: kernel test robot <lkp@...el.com>, Tejun Heo <tj@...nel.org>, Lai
 Jiangshan <jiangshanlai@...il.com>, Aaron Tomlin <atomlin@...mlin.com>,
	<linux-kernel@...r.kernel.org>
CC: <oe-kbuild-all@...ts.linux.dev>, Wenchao Hao <haowenchao22@...il.com>
Subject: Re: [PATCH] workqueue: Fix rescuer task's name truncated

On 2024/5/13 15:35, kernel test robot wrote:
> Hi Wenchao,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on tj-wq/for-next]
> [also build test WARNING on linus/master v6.9 next-20240510]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Wenchao-Hao/workqueue-Fix-rescuer-task-s-name-truncated/20240513-110849
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-next
> patch link:    https://lore.kernel.org/r/20240513030639.3772468-1-haowenchao2%40huawei.com
> patch subject: [PATCH] workqueue: Fix rescuer task's name truncated
> config: openrisc-allnoconfig (https://download.01.org/0day-ci/archive/20240513/202405131400.sEYZHYk2-lkp@intel.com/config)
> compiler: or1k-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240513/202405131400.sEYZHYk2-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202405131400.sEYZHYk2-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>     kernel/workqueue.c: In function 'init_rescuer':
>>> kernel/workqueue.c:5558:57: warning: '%s' directive output may be truncated writing up to 31 bytes into a region of size 24 [-Wformat-truncation=]
>      5558 |         snprintf(rescuer->desc, sizeof(rescuer->desc), "%s", wq->name);
>           |                                                         ^~
>     kernel/workqueue.c:5558:9: note: 'snprintf' output between 1 and 32 bytes into a destination of size 24
>      5558 |         snprintf(rescuer->desc, sizeof(rescuer->desc), "%s", wq->name);
>           |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> 
> vim +5558 kernel/workqueue.c
> 
>    5528	
>    5529	/*
>    5530	 * Workqueues which may be used during memory reclaim should have a rescuer
>    5531	 * to guarantee forward progress.
>    5532	 */
>    5533	static int init_rescuer(struct workqueue_struct *wq)
>    5534	{
>    5535		struct worker *rescuer;
>    5536		int ret;
>    5537	
>    5538		if (!(wq->flags & WQ_MEM_RECLAIM))
>    5539			return 0;
>    5540	
>    5541		rescuer = alloc_worker(NUMA_NO_NODE);
>    5542		if (!rescuer) {
>    5543			pr_err("workqueue: Failed to allocate a rescuer for wq \"%s\"\n",
>    5544			       wq->name);
>    5545			return -ENOMEM;
>    5546		}
>    5547	
>    5548		rescuer->rescue_wq = wq;
>    5549		rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R");
>    5550		if (IS_ERR(rescuer->task)) {
>    5551			ret = PTR_ERR(rescuer->task);
>    5552			pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
>    5553			       wq->name, ERR_PTR(ret));
>    5554			kfree(rescuer);
>    5555			return ret;
>    5556		}
>    5557	
>> 5558		snprintf(rescuer->desc, sizeof(rescuer->desc), "%s", wq->name);

This is because commit 31c89007285d3 ("workqueue.c: Increase workqueue name length") increase
WQ_NAME_LEN from 24 to 32, but forget to increase WORKER_DESC_LEN (WORKER_DESC_LEN should equal
to WQ_NAME_LEN ).

Same usage can be found in process_one_work(), it called strscpy() which would not WARNING.
I would add following changes and post V2:

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 158784dd189a..72031fa80414 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -92,7 +92,7 @@ enum wq_misc_consts {
         WORK_BUSY_RUNNING       = 1 << 1,
  
         /* maximum string length for set_worker_desc() */
-       WORKER_DESC_LEN         = 24,
+       WORKER_DESC_LEN         = 32,
  };
  
  /* Convenience constants - of type 'unsigned long', not 'enum'! */


>    5559	
>    5560		wq->rescuer = rescuer;
>    5561		if (wq->flags & WQ_UNBOUND)
>    5562			kthread_bind_mask(rescuer->task, wq_unbound_cpumask);
>    5563		else
>    5564			kthread_bind_mask(rescuer->task, cpu_possible_mask);
>    5565		wake_up_process(rescuer->task);
>    5566	
>    5567		return 0;
>    5568	}
>    5569	
>