linux-kernel - Re: [PATCH v8 7/8] vhost: Add check for inherit

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Message-ID: <d35istatjtnr42x4gwpwlgx627pl3ntqua3kde7fymtotl676i@jxxxkrii6rue>
Date: Tue, 1 Apr 2025 15:59:26 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: jasowang@...hat.com, mst@...hat.com, michael.christie@...cle.com, 
	linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v8 7/8] vhost: Add check for inherit_owner status

On Fri, Mar 28, 2025 at 06:02:51PM +0800, Cindy Lu wrote:
>The VHOST_NEW_WORKER requires the inherit_owner
>setting to be true. So we need to add a check for this.
>
>Signed-off-by: Cindy Lu <lulu@...hat.com>
>---
> drivers/vhost/vhost.c | 7 +++++++
> 1 file changed, 7 insertions(+)

IMHO we should squash this patch also with the previous one, or do this 
before allowing the user to change inherit_owner, otherwise bisection 
can be broken.

Thanks,
Stefano

>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index ff930c2e5b78..fb0c7fb43f78 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -1018,6 +1018,13 @@ long vhost_worker_ioctl(struct vhost_dev *dev, unsigned int ioctl,
> 	switch (ioctl) {
> 	/* dev worker ioctls */
> 	case VHOST_NEW_WORKER:
>+		/*
>+		 * 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 (!dev->inherit_owner)
>+			return -EFAULT;
> 		ret = vhost_new_worker(dev, &state);
> 		if (!ret && copy_to_user(argp, &state, sizeof(state)))
> 			ret = -EFAULT;
>-- 
>2.45.0
>