netdev - Re: [PATCH v3 8/9] vhost_scsi: Add check for inherit

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Message-ID: <3864ae3b-d6cd-4227-b4bb-56e014c71667@oracle.com>
Date: Mon, 25 Nov 2024 09:00:07 -0600
From: Mike Christie <michael.christie@...cle.com>
To: Cindy Lu <lulu@...hat.com>, jasowang@...hat.com, mst@...hat.com,
        sgarzare@...hat.com, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 8/9] vhost_scsi: Add check for inherit_owner status

On 11/5/24 1:25 AM, Cindy Lu wrote:
> The vhost_scsi VHOST_NEW_WORKER requires the inherit_owner
> setting to be true. So we need to implement a check for this.
> 
> Signed-off-by: Cindy Lu <lulu@...hat.com>
> ---
>  drivers/vhost/scsi.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 006ffacf1c56..05290298b5ab 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -2083,6 +2083,11 @@ vhost_scsi_ioctl(struct file *f,
>  			return -EFAULT;
>  		return vhost_scsi_set_features(vs, features);
>  	case VHOST_NEW_WORKER:
> +		/*vhost-scsi VHOST_NEW_WORKER requires inherit_owner to be true*/

The above comment is not really needed since we know it's
required from the check being added.

If you want to add a comment, I think it should describe why we
require it as that's not obvious from just looking at the check.

So maybe a more useful comment would be:

/*
 * vhost_tasks will account for worker threads under the parent's
 * NPROC value but kthreads do not. To avoid userspace overflowing
 * the system with worker threads inherit_owner must be true.
 */

> +		if (vs->dev.inherit_owner != true)

This check and the comment would apply to all vhost drivers so it
should go in vhost_worker_ioctl's VHOST_NEW_WORKER handling.

> +			return -EFAULT;
> +
> +		fallthrough;
>  	case VHOST_FREE_WORKER:
>  	case VHOST_ATTACH_VRING_WORKER:
>  	case VHOST_GET_VRING_WORKER: