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SubjectRe: [RFC PATCH] vhost-vdpa: mark vhost device invalid to reflect vdpa device unregistration
On Mon, Jul 05, 2021 at 02:22:04AM +0530, gautam.dawar@xilinx.com wrote:
> From: Gautam Dawar <gdawar@xilinx.com>
>
> As mentioned in Bug 213179, any malicious user-space application can render
> a module registering a vDPA device to hang forever. This will typically
> surface when vdpa_device_unregister() is called from the function
> responsible for module unload, leading rmmod commands to not return.
>
> This patch unblocks the caller module by continuing with the clean-up
> but after marking the vhost device as unavailable. For future requests
> from user-space application, the vhost device availability is checked
> first and if it has gone unavailable, such requests are denied.
>
> Signed-off-by: Gautam Dawar <gdawar@xilinx.com>


I don't seem mappings handled below. Did I miss it?

> ---
> drivers/vhost/vdpa.c | 45 ++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 39 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index e4b7d26649d8..623bc7f0c0ca 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -47,6 +47,7 @@ struct vhost_vdpa {
> int minor;
> struct eventfd_ctx *config_ctx;
> int in_batch;
> + int dev_invalid;
> struct vdpa_iova_range range;
> };
>
> @@ -61,6 +62,11 @@ static void handle_vq_kick(struct vhost_work *work)
> struct vhost_vdpa *v = container_of(vq->dev, struct vhost_vdpa, vdev);
> const struct vdpa_config_ops *ops = v->vdpa->config;
>
> + if (v->dev_invalid) {
> + dev_info(&v->dev,
> + "%s: vhost_vdpa device unavailable\n", __func__);
> + return;
> + }
> ops->kick_vq(v->vdpa, vq - v->vqs);
> }
>
> @@ -120,6 +126,11 @@ static void vhost_vdpa_reset(struct vhost_vdpa *v)
> {
> struct vdpa_device *vdpa = v->vdpa;
>
> + if (v->dev_invalid) {
> + dev_info(&v->dev,
> + "%s: vhost_vdpa device unavailable\n", __func__);
> + return;
> + }
> vdpa_reset(vdpa);
> v->in_batch = 0;
> }
> @@ -367,6 +378,11 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
> u32 idx;
> long r;
>
> + if (v->dev_invalid) {
> + dev_info(&v->dev,
> + "%s: vhost_vdpa device unavailable\n", __func__);
> + return -ENODEV;
> + }
> r = get_user(idx, (u32 __user *)argp);
> if (r < 0)
> return r;
> @@ -450,6 +466,11 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> return 0;
> }
>
> + if (v->dev_invalid) {
> + dev_info(&v->dev,
> + "%s: vhost_vdpa device unavailable\n", __func__);
> + return -ENODEV;
> + }
> mutex_lock(&d->mutex);
>
> switch (cmd) {
> @@ -745,8 +766,13 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
> const struct vdpa_config_ops *ops = vdpa->config;
> int r = 0;
>
> - mutex_lock(&dev->mutex);
> + if (v->dev_invalid) {
> + dev_info(&v->dev,
> + "%s: vhost_vdpa device unavailable\n", __func__);
> + return -ENODEV;
> + }
>
> + mutex_lock(&dev->mutex);
> r = vhost_dev_check_owner(dev);
> if (r)
> goto unlock;
> @@ -949,6 +975,11 @@ static vm_fault_t vhost_vdpa_fault(struct vm_fault *vmf)
> struct vm_area_struct *vma = vmf->vma;
> u16 index = vma->vm_pgoff;
>
> + if (v->dev_invalid) {
> + dev_info(&v->dev,
> + "%s: vhost_vdpa device unavailable\n", __func__);
> + return VM_FAULT_NOPAGE;
> + }
> notify = ops->get_vq_notification(vdpa, index);
>
> vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> @@ -1091,11 +1122,13 @@ static void vhost_vdpa_remove(struct vdpa_device *vdpa)
> opened = atomic_cmpxchg(&v->opened, 0, 1);
> if (!opened)
> break;
> - wait_for_completion_timeout(&v->completion,
> - msecs_to_jiffies(1000));
> - dev_warn_once(&v->dev,
> - "%s waiting for /dev/%s to be closed\n",
> - __func__, dev_name(&v->dev));
> + if (!wait_for_completion_timeout(&v->completion,
> + msecs_to_jiffies(1000))) {
> + dev_warn(&v->dev,
> + "%s /dev/%s in use, continue..\n",
> + __func__, dev_name(&v->dev));
> + break;
> + }

When you have an arbitrary timeout you know something's not entirely
robust ...

> } while (1);
>
> put_device(&v->dev);
> + v->dev_invalid = true;
> --
> 2.30.1

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