Commit message: vhost-vdpa: fix use-after-free of v->config_ctx

When the 'v->config_ctx' eventfd_ctx reference is released we didn't
set it to NULL. So if the same character device (e.g. /dev/vhost-vdpa-0)
is re-opened, the 'v->config_ctx' is invalid and calling again
vhost_vdpa_config_put() causes use-after-free issues like the
following refcount_t underflow:

    refcount_t: underflow; use-after-free.
    WARNING: CPU: 2 PID: 872 at lib/refcount.c:28 refcount_warn_saturate+0xae/0xf0
    RIP: 0010:refcount_warn_saturate+0xae/0xf0
    Call Trace:
     eventfd_ctx_put+0x5b/0x70
     vhost_vdpa_release+0xcd/0x150 [vhost_vdpa]
     __fput+0x8e/0x240
     ____fput+0xe/0x10
     task_work_run+0x66/0xa0
     exit_to_user_mode_prepare+0x118/0x120
     syscall_exit_to_user_mode+0x21/0x50
     ? __x64_sys_close+0x12/0x40
     do_syscall_64+0x45/0x50
     entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: 776f395004d8 ("vhost_vdpa: Support config interrupt in vdpa")
Cc: lingshan.zhu@intel.com
Cc: stable@vger.kernel.org
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20210311135257.109460-2-sgarzare@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
CVE: CVE-2021-29266
CWE: CWE-416
Vulnerability description: An issue was discovered in the Linux kernel before 5.11.9. drivers/vhost/vdpa.c has a use-after-free because v->config_ctx has an invalid value upon re-opening a character device, aka CID-f6bbf0010ba0.

Project: linux
File: vdpa.c

static int vhost_vdpa_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct vhost_vdpa *v = vma->vm_file->private_data;
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	struct vdpa_notification_area notify;
	unsigned long index = vma->vm_pgoff;

	if (vma->vm_end - vma->vm_start != PAGE_SIZE)
		return -EINVAL;
	if ((vma->vm_flags & VM_SHARED) == 0)
		return -EINVAL;
	if (vma->vm_flags & VM_READ)
		return -EINVAL;
	if (index > 65535)
		return -EINVAL;
	if (!ops->get_vq_notification)
		return -ENOTSUPP;

	/* To be safe and easily modelled by userspace, We only
	 * support the doorbell which sits on the page boundary and
	 * does not share the page with other registers.
	 */
	notify = ops->get_vq_notification(vdpa, index);
	if (notify.addr & (PAGE_SIZE - 1))
		return -EINVAL;
	if (vma->vm_end - vma->vm_start != notify.size)
		return -ENOTSUPP;

	vma->vm_ops = &vhost_vdpa_vm_ops;
	return 0;
}

Project: linux
File: vdpa.c

static void vhost_vdpa_reset(struct vhost_vdpa *v)
{
	struct vdpa_device *vdpa = v->vdpa;

	vdpa_reset(vdpa);
	v->in_batch = 0;
}

Project: linux
File: vdpa.c

static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
				   void __user *argp)
{
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	struct vdpa_vq_state vq_state;
	struct vdpa_callback cb;
	struct vhost_virtqueue *vq;
	struct vhost_vring_state s;
	u32 idx;
	long r;

	r = get_user(idx, (u32 __user *)argp);
	if (r < 0)
		return r;

	if (idx >= v->nvqs)
		return -ENOBUFS;

	idx = array_index_nospec(idx, v->nvqs);
	vq = &v->vqs[idx];

	switch (cmd) {
	case VHOST_VDPA_SET_VRING_ENABLE:
		if (copy_from_user(&s, argp, sizeof(s)))
			return -EFAULT;
		ops->set_vq_ready(vdpa, idx, s.num);
		return 0;
	case VHOST_GET_VRING_BASE:
		r = ops->get_vq_state(v->vdpa, idx, &vq_state);
		if (r)
			return r;

		vq->last_avail_idx = vq_state.avail_index;
		break;
	}

	r = vhost_vring_ioctl(&v->vdev, cmd, argp);
	if (r)
		return r;

	switch (cmd) {
	case VHOST_SET_VRING_ADDR:
		if (ops->set_vq_address(vdpa, idx,
					(u64)(uintptr_t)vq->desc,
					(u64)(uintptr_t)vq->avail,
					(u64)(uintptr_t)vq->used))
			r = -EINVAL;
		break;

	case VHOST_SET_VRING_BASE:
		vq_state.avail_index = vq->last_avail_idx;
		if (ops->set_vq_state(vdpa, idx, &vq_state))
			r = -EINVAL;
		break;

	case VHOST_SET_VRING_CALL:
		if (vq->call_ctx.ctx) {
			cb.callback = vhost_vdpa_virtqueue_cb;
			cb.private = vq;
		} else {
			cb.callback = NULL;
			cb.private = NULL;
		}
		ops->set_vq_cb(vdpa, idx, &cb);
		vhost_vdpa_setup_vq_irq(v, idx);
		break;

	case VHOST_SET_VRING_NUM:
		ops->set_vq_num(vdpa, idx, vq->num);
		break;
	}

	return r;
}

Project: linux
File: vdpa.c

static void vhost_vdpa_iotlb_unmap(struct vhost_vdpa *v, u64 start, u64 last)
{
	struct vhost_dev *dev = &v->vdev;
	struct vhost_iotlb *iotlb = dev->iotlb;
	struct vhost_iotlb_map *map;
	struct page *page;
	unsigned long pfn, pinned;

	while ((map = vhost_iotlb_itree_first(iotlb, start, last)) != NULL) {
		pinned = map->size >> PAGE_SHIFT;
		for (pfn = map->addr >> PAGE_SHIFT;
		     pinned > 0; pfn++, pinned--) {
			page = pfn_to_page(pfn);
			if (map->perm & VHOST_ACCESS_WO)
				set_page_dirty_lock(page);
			unpin_user_page(page);
		}
		atomic64_sub(map->size >> PAGE_SHIFT, &dev->mm->pinned_vm);
		vhost_iotlb_map_free(iotlb, map);
	}
}

Project: linux
File: vdpa.c

static int vhost_vdpa_map(struct vhost_vdpa *v,
			  u64 iova, u64 size, u64 pa, u32 perm)
{
	struct vhost_dev *dev = &v->vdev;
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	int r = 0;

	r = vhost_iotlb_add_range(dev->iotlb, iova, iova + size - 1,
				  pa, perm);
	if (r)
		return r;

	if (ops->dma_map) {
		r = ops->dma_map(vdpa, iova, size, pa, perm);
	} else if (ops->set_map) {
		if (!v->in_batch)
			r = ops->set_map(vdpa, dev->iotlb);
	} else {
		r = iommu_map(v->domain, iova, pa, size,
			      perm_to_iommu_flags(perm));
	}

	if (r)
		vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1);
	else
		atomic64_add(size >> PAGE_SHIFT, &dev->mm->pinned_vm);

	return r;
}

Project: linux
File: vdpa.c

static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
					   struct vhost_iotlb_msg *msg)
{
	struct vhost_dev *dev = &v->vdev;
	struct vhost_iotlb *iotlb = dev->iotlb;
	struct page **page_list;
	unsigned long list_size = PAGE_SIZE / sizeof(struct page *);
	unsigned int gup_flags = FOLL_LONGTERM;
	unsigned long npages, cur_base, map_pfn, last_pfn = 0;
	unsigned long lock_limit, sz2pin, nchunks, i;
	u64 iova = msg->iova;
	long pinned;
	int ret = 0;

	if (msg->iova < v->range.first ||
	    msg->iova + msg->size - 1 > v->range.last)
		return -EINVAL;

	if (vhost_iotlb_itree_first(iotlb, msg->iova,
				    msg->iova + msg->size - 1))
		return -EEXIST;

	/* Limit the use of memory for bookkeeping */
	page_list = (struct page **) __get_free_page(GFP_KERNEL);
	if (!page_list)
		return -ENOMEM;

	if (msg->perm & VHOST_ACCESS_WO)
		gup_flags |= FOLL_WRITE;

	npages = PAGE_ALIGN(msg->size + (iova & ~PAGE_MASK)) >> PAGE_SHIFT;
	if (!npages) {
		ret = -EINVAL;
		goto free;
	}

	mmap_read_lock(dev->mm);

	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
	if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
		ret = -ENOMEM;
		goto unlock;
	}

	cur_base = msg->uaddr & PAGE_MASK;
	iova &= PAGE_MASK;
	nchunks = 0;

	while (npages) {
		sz2pin = min_t(unsigned long, npages, list_size);
		pinned = pin_user_pages(cur_base, sz2pin,
					gup_flags, page_list, NULL);
		if (sz2pin != pinned) {
			if (pinned < 0) {
				ret = pinned;
			} else {
				unpin_user_pages(page_list, pinned);
				ret = -ENOMEM;
			}
			goto out;
		}
		nchunks++;

		if (!last_pfn)
			map_pfn = page_to_pfn(page_list[0]);

		for (i = 0; i < pinned; i++) {
			unsigned long this_pfn = page_to_pfn(page_list[i]);
			u64 csize;

			if (last_pfn && (this_pfn != last_pfn + 1)) {
				/* Pin a contiguous chunk of memory */
				csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT;
				ret = vhost_vdpa_map(v, iova, csize,
						     map_pfn << PAGE_SHIFT,
						     msg->perm);
				if (ret) {
					/*
					 * Unpin the pages that are left unmapped
					 * from this point on in the current
					 * page_list. The remaining outstanding
					 * ones which may stride across several
					 * chunks will be covered in the common
					 * error path subsequently.
					 */
					unpin_user_pages(&page_list[i],
							 pinned - i);
					goto out;
				}

				map_pfn = this_pfn;
				iova += csize;
				nchunks = 0;
			}

			last_pfn = this_pfn;
		}

		cur_base += pinned << PAGE_SHIFT;
		npages -= pinned;
	}

	/* Pin the rest chunk */
	ret = vhost_vdpa_map(v, iova, (last_pfn - map_pfn + 1) << PAGE_SHIFT,
			     map_pfn << PAGE_SHIFT, msg->perm);
out:
	if (ret) {
		if (nchunks) {
			unsigned long pfn;

			/*
			 * Unpin the outstanding pages which are yet to be
			 * mapped but haven't due to vdpa_map() or
			 * pin_user_pages() failure.
			 *
			 * Mapped pages are accounted in vdpa_map(), hence
			 * the corresponding unpinning will be handled by
			 * vdpa_unmap().
			 */
			WARN_ON(!last_pfn);
			for (pfn = map_pfn; pfn <= last_pfn; pfn++)
				unpin_user_page(pfn_to_page(pfn));
		}
		vhost_vdpa_unmap(v, msg->iova, msg->size);
	}
unlock:
	mmap_read_unlock(dev->mm);
free:
	free_page((unsigned long)page_list);
	return ret;
}

Project: linux
File: vdpa.c

static long vhost_vdpa_set_status(struct vhost_vdpa *v, u8 __user *statusp)
{
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	u8 status, status_old;
	int nvqs = v->nvqs;
	u16 i;

	if (copy_from_user(&status, statusp, sizeof(status)))
		return -EFAULT;

	status_old = ops->get_status(vdpa);

	/*
	 * Userspace shouldn't remove status bits unless reset the
	 * status to 0.
	 */
	if (status != 0 && (ops->get_status(vdpa) & ~status) != 0)
		return -EINVAL;

	ops->set_status(vdpa, status);

	if ((status & VIRTIO_CONFIG_S_DRIVER_OK) && !(status_old & VIRTIO_CONFIG_S_DRIVER_OK))
		for (i = 0; i < nvqs; i++)
			vhost_vdpa_setup_vq_irq(v, i);

	if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) && !(status & VIRTIO_CONFIG_S_DRIVER_OK))
		for (i = 0; i < nvqs; i++)
			vhost_vdpa_unsetup_vq_irq(v, i);

	return 0;
}

Project: linux
File: vdpa.c

static void vhost_vdpa_set_iova_range(struct vhost_vdpa *v)
{
	struct vdpa_iova_range *range = &v->range;
	struct iommu_domain_geometry geo;
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;

	if (ops->get_iova_range) {
		*range = ops->get_iova_range(vdpa);
	} else if (v->domain &&
		   !iommu_domain_get_attr(v->domain,
		   DOMAIN_ATTR_GEOMETRY, &geo) &&
		   geo.force_aperture) {
		range->first = geo.aperture_start;
		range->last = geo.aperture_end;
	} else {
		range->first = 0;
		range->last = ULLONG_MAX;
	}
}

Project: linux
File: vdpa.c

static vm_fault_t vhost_vdpa_fault(struct vm_fault *vmf)
{
	struct vhost_vdpa *v = vmf->vma->vm_file->private_data;
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	struct vdpa_notification_area notify;
	struct vm_area_struct *vma = vmf->vma;
	u16 index = vma->vm_pgoff;

	notify = ops->get_vq_notification(vdpa, index);

	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
	if (remap_pfn_range(vma, vmf->address & PAGE_MASK,
			    notify.addr >> PAGE_SHIFT, PAGE_SIZE,
			    vma->vm_page_prot))
		return VM_FAULT_SIGBUS;

	return VM_FAULT_NOPAGE;
}

Project: linux
File: vdpa.c

static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
					struct vhost_iotlb_msg *msg)
{
	struct vhost_vdpa *v = container_of(dev, struct vhost_vdpa, vdev);
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	int r = 0;

	r = vhost_dev_check_owner(dev);
	if (r)
		return r;

	switch (msg->type) {
	case VHOST_IOTLB_UPDATE:
		r = vhost_vdpa_process_iotlb_update(v, msg);
		break;
	case VHOST_IOTLB_INVALIDATE:
		vhost_vdpa_unmap(v, msg->iova, msg->size);
		break;
	case VHOST_IOTLB_BATCH_BEGIN:
		v->in_batch = true;
		break;
	case VHOST_IOTLB_BATCH_END:
		if (v->in_batch && ops->set_map)
			ops->set_map(vdpa, dev->iotlb);
		v->in_batch = false;
		break;
	default:
		r = -EINVAL;
		break;
	}

	return r;
}

Project: linux
File: vdpa.c

static long vhost_vdpa_set_config_call(struct vhost_vdpa *v, u32 __user *argp)
{
	struct vdpa_callback cb;
	int fd;
	struct eventfd_ctx *ctx;

	cb.callback = vhost_vdpa_config_cb;
	cb.private = v->vdpa;
	if (copy_from_user(&fd, argp, sizeof(fd)))
		return  -EFAULT;

	ctx = fd == VHOST_FILE_UNBIND ? NULL : eventfd_ctx_fdget(fd);
	swap(ctx, v->config_ctx);

	if (!IS_ERR_OR_NULL(ctx))
		eventfd_ctx_put(ctx);

	if (IS_ERR(v->config_ctx))
		return PTR_ERR(v->config_ctx);

	v->vdpa->config->set_config_cb(v->vdpa, &cb);

	return 0;
}

Project: linux
File: vdpa.c

static long vhost_vdpa_set_config(struct vhost_vdpa *v,
				  struct vhost_vdpa_config __user *c)
{
	struct vdpa_device *vdpa = v->vdpa;
	const struct vdpa_config_ops *ops = vdpa->config;
	struct vhost_vdpa_config config;
	unsigned long size = offsetof(struct vhost_vdpa_config, buf);
	u8 *buf;

	if (copy_from_user(&config, c, size))
		return -EFAULT;
	if (vhost_vdpa_config_validate(v, &config))
		return -EINVAL;

	buf = vmemdup_user(c->buf, config.len);
	if (IS_ERR(buf))
		return PTR_ERR(buf);

	ops->set_config(vdpa, config.off, buf, config.len);

	kvfree(buf);
	return 0;
}

Project: linux
File: vdpa.c

static int vhost_vdpa_open(struct inode *inode, struct file *filep)
{
	struct vhost_vdpa *v;
	struct vhost_dev *dev;
	struct vhost_virtqueue **vqs;
	int nvqs, i, r, opened;

	v = container_of(inode->i_cdev, struct vhost_vdpa, cdev);

	opened = atomic_cmpxchg(&v->opened, 0, 1);
	if (opened)
		return -EBUSY;

	nvqs = v->nvqs;
	vhost_vdpa_reset(v);

	vqs = kmalloc_array(nvqs, sizeof(*vqs), GFP_KERNEL);
	if (!vqs) {
		r = -ENOMEM;
		goto err;
	}

	dev = &v->vdev;
	for (i = 0; i < nvqs; i++) {
		vqs[i] = &v->vqs[i];
		vqs[i]->handle_kick = handle_vq_kick;
	}
	vhost_dev_init(dev, vqs, nvqs, 0, 0, 0, false,
		       vhost_vdpa_process_iotlb_msg);

	dev->iotlb = vhost_iotlb_alloc(0, 0);
	if (!dev->iotlb) {
		r = -ENOMEM;
		goto err_init_iotlb;
	}

	r = vhost_vdpa_alloc_domain(v);
	if (r)
		goto err_init_iotlb;

	vhost_vdpa_set_iova_range(v);

	filep->private_data = v;

	return 0;

err_init_iotlb:
	vhost_dev_cleanup(&v->vdev);
	kfree(vqs);
err:
	atomic_dec(&v->opened);
	return r;
}

Project: linux
File: vdpa.c

static int vhost_vdpa_release(struct inode *inode, struct file *filep)
{
	struct vhost_vdpa *v = filep->private_data;
	struct vhost_dev *d = &v->vdev;

	mutex_lock(&d->mutex);
	filep->private_data = NULL;
	vhost_vdpa_reset(v);
	vhost_dev_stop(&v->vdev);
	vhost_vdpa_iotlb_free(v);
	vhost_vdpa_free_domain(v);
	vhost_vdpa_config_put(v);
	vhost_vdpa_clean_irq(v);
	vhost_dev_cleanup(&v->vdev);
	kfree(v->vdev.vqs);
	mutex_unlock(&d->mutex);

	atomic_dec(&v->opened);
	complete(&v->completion);

	return 0;
}

Project: linux
File: vdpa.c

static int vhost_vdpa_probe(struct vdpa_device *vdpa)
{
	const struct vdpa_config_ops *ops = vdpa->config;
	struct vhost_vdpa *v;
	int minor;
	int r;

	/* Currently, we only accept the network devices. */
	if (ops->get_device_id(vdpa) != VIRTIO_ID_NET)
		return -ENOTSUPP;

	v = kzalloc(sizeof(*v), GFP_KERNEL | __GFP_RETRY_MAYFAIL);
	if (!v)
		return -ENOMEM;

	minor = ida_simple_get(&vhost_vdpa_ida, 0,
			       VHOST_VDPA_DEV_MAX, GFP_KERNEL);
	if (minor < 0) {
		kfree(v);
		return minor;
	}

	atomic_set(&v->opened, 0);
	v->minor = minor;
	v->vdpa = vdpa;
	v->nvqs = vdpa->nvqs;
	v->virtio_id = ops->get_device_id(vdpa);

	device_initialize(&v->dev);
	v->dev.release = vhost_vdpa_release_dev;
	v->dev.parent = &vdpa->dev;
	v->dev.devt = MKDEV(MAJOR(vhost_vdpa_major), minor);
	v->vqs = kmalloc_array(v->nvqs, sizeof(struct vhost_virtqueue),
			       GFP_KERNEL);
	if (!v->vqs) {
		r = -ENOMEM;
		goto err;
	}

	r = dev_set_name(&v->dev, "vhost-vdpa-%u", minor);
	if (r)
		goto err;

	cdev_init(&v->cdev, &vhost_vdpa_fops);
	v->cdev.owner = THIS_MODULE;

	r = cdev_device_add(&v->cdev, &v->dev);
	if (r)
		goto err;

	init_completion(&v->completion);
	vdpa_set_drvdata(vdpa, v);

	return 0;

err:
	put_device(&v->dev);
	return r;
}

Project: linux
File: vdpa.c

static int vhost_vdpa_config_validate(struct vhost_vdpa *v,
				      struct vhost_vdpa_config *c)
{
	long size = 0;

	switch (v->virtio_id) {
	case VIRTIO_ID_NET:
		size = sizeof(struct virtio_net_config);
		break;
	}

	if (c->len == 0)
		return -EINVAL;

	if (c->len > size - c->off)
		return -E2BIG;

	return 0;
}