[v8] vhost: Add support of kthread API

[PATCH v8 7/8] vhost: Add check for inherit_owner status

Posted by Cindy Lu 8 months, 3 weeks ago

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@redhat.com>
---
 drivers/vhost/vhost.c | 7 +++++++
 1 file changed, 7 insertions(+)

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

Re: [PATCH v8 7/8] vhost: Add check for inherit_owner status

Posted by Stefano Garzarella 8 months, 3 weeks ago

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@redhat.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
>

Re: [PATCH v8 7/8] vhost: Add check for inherit_owner status

Posted by Cindy Lu 8 months, 2 weeks ago

On Tue, Apr 1, 2025 at 9:59 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> 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@redhat.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
>
Sure, will do
Thanks
Cindy
> >
> >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
> >
>