linux-kernel - Re: [PATCH] workqueue: fix null-ptr-deref on __alloc

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Message-ID: <Zr4lN63t25Og5/0G@DUT025-TGLU.fm.intel.com>
Date: Thu, 15 Aug 2024 15:56:39 +0000
From: Matthew Brost <matthew.brost@...el.com>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
CC: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] workqueue: fix null-ptr-deref on __alloc_workqueue()
 error

On Thu, Aug 15, 2024 at 04:24:27PM +0900, Sergey Senozhatsky wrote:
> On (24/08/15 16:09), Sergey Senozhatsky wrote:
> > On (24/08/15 16:02), Sergey Senozhatsky wrote:
> > Oh, okay, so this is related to [1]
> > 
> > 	workqueue: Split alloc_workqueue into internal function and lockdep init
> > 
> > Cc-ing Matthew on this.
> > 
> > [1] https://lore.kernel.org/all/20240809222827.3211998-2-matthew.brost@intel.com/
> 
> Matthew, did you mean to do something like below instead?
> Otherwise it breaks boot for me.
> 

Yikes, my bad. My change worked locally and in Intel's CI for Xe [2]. So
I did not realize this was an issue the way I had it coded. 

I believe you when you say this is an issue.

With that, the way I coded alloc_ordered_workqueue_lockdep_map could
also be dangerous. Thinking that also should also be changed back to a
macro too.

Let's see what Tejon thinks?

Matt

[2] https://patchwork.freedesktop.org/series/136701/ 

> ---
> 
> diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> index 7a2f4cbbe8b2..55e0e69ee604 100644
> --- a/kernel/workqueue.c
> +++ b/kernel/workqueue.c
> @@ -5615,12 +5615,11 @@ static void wq_adjust_max_active(struct workqueue_struct *wq)
>  	} while (activated);
>  }
>  
> -__printf(1, 4)
>  static struct workqueue_struct *__alloc_workqueue(const char *fmt,
>  						  unsigned int flags,
> -						  int max_active, ...)
> +						  int max_active,
> +						  va_list args)
>  {
> -	va_list args;
>  	struct workqueue_struct *wq;
>  	size_t wq_size;
>  	int name_len;
> @@ -5652,9 +5651,7 @@ static struct workqueue_struct *__alloc_workqueue(const char *fmt,
>  			goto err_free_wq;
>  	}
>  
> -	va_start(args, max_active);
>  	name_len = vsnprintf(wq->name, sizeof(wq->name), fmt, args);
> -	va_end(args);
>  
>  	if (name_len >= WQ_NAME_LEN)
>  		pr_warn_once("workqueue: name exceeds WQ_NAME_LEN. Truncating to: %s\n",