linux-kernel - Re: [PATCH] workqueue: missing NOT while checking if Workqueue is offline

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 28 May 2022 22:25:51 -0300
From:   Geraldo Nascimento <geraldogabriel@...il.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     Lai Jiangshan <jiangshanlai@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] workqueue: missing NOT while checking if Workqueue is
 offline

On Sat, May 28, 2022 at 05:07:08PM -0300, Geraldo Nascimento wrote:
> Greetings,
> 

Hi, again,

> This is a one-character patch but very important as the kernel workqueue
> __cancel_work_timer will cancel active work without the NOT operator
> added.
> 
> During early boot wq_online is false so with the NOT added it will evaluate
> to true. Conversely, after boot is done, workqueue

I meant wq_online. After boot, wq_online will evaluate to true, current
code might as well have an if (true) there. I hurried up the patch
because if I'm right this is a major show stopper to drivers that make
use of cancel_work_timer(). I hit it through amdgpu in conjuction with amdkfd.

> is now true and we want
> it to evaluate to false because otherwise it will cancel important work.
> 
> Signed-off-by: Geraldo Nascimento <geraldogabriel@...il.com>
> 
> --- workqueue.c	2022-05-28 16:54:12.024176123 -0300
> +++ workqueue.c	2022-05-28 16:54:37.698176135 -0300
> @@ -3158,7 +3158,7 @@ static bool __cancel_work_timer(struct w
>  	 * This allows canceling during early boot.  We know that @work
>  	 * isn't executing.
>  	 */
> -	if (wq_online)
> +	if (!wq_online)
>  		__flush_work(work, true);
>  
>  	clear_work_data(work);