virtio: last minute fixes

Some fixes that took a while to get ready. Not regressions,
 but they look safe and seem to be worth to have.
 
 Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

Pull virtio fixes from Michael Tsirkin:
 "Some last minute fixes that took a while to get ready. Not
  regressions, but they look safe and seem to be worth to have"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  tools/virtio: handle fallout from folio work
  tools/virtio: fix virtio_test execution
  vhost: remove avail_event arg from vhost_update_avail_event()
  virtio: drop default for virtio-mem
  vdpa: fix use-after-free on vp_vdpa_remove
  virtio-blk: Remove BUG_ON() in virtio_queue_rq()
  virtio-blk: Don't use MAX_DISCARD_SEGMENTS if max_discard_seg is zero
  vhost: fix hung thread due to erroneous iotlb entries
  vduse: Fix returning wrong type in vduse_domain_alloc_iova()
  vdpa/mlx5: add validation for VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET command
  vdpa/mlx5: should verify CTRL_VQ feature exists for MQ
  vdpa: factor out vdpa_set_features_unlocked for vdpa internal use
  virtio_console: break out of buf poll on remove
  virtio: document virtio_reset_device
  virtio: acknowledge all features before access
  virtio: unexport virtio_finalize_features

drivers/block/virtio_blk.c

@@ -76,9 +76,6 @@ struct virtio_blk {
 	 */
 	refcount_t refs;
 
-	/* What host tells us, plus 2 for header & tailer. */
-	unsigned int sg_elems;
-
 	/* Ida index - used to track minor number allocations. */
 	int index;
 
@@ -322,8 +319,6 @@ static blk_status_t virtio_queue_rq(struct blk_mq_hw_ctx *hctx,
 	blk_status_t status;
 	int err;
 
-	BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
-
 	status = virtblk_setup_cmd(vblk->vdev, req, vbr);
 	if (unlikely(status))
 		return status;
@@ -783,8 +778,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 	/* Prevent integer overflows and honor max vq size */
 	sg_elems = min_t(u32, sg_elems, VIRTIO_BLK_MAX_SG_ELEMS - 2);
 
-	/* We need extra sg elements at head and tail. */
-	sg_elems += 2;
 	vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);
 	if (!vblk) {
 		err = -ENOMEM;
@@ -796,7 +789,6 @@ static int virtblk_probe(struct virtio_device *vdev)
 	mutex_init(&vblk->vdev_mutex);
 
 	vblk->vdev = vdev;
-	vblk->sg_elems = sg_elems;
 
 	INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
 
@@ -853,7 +845,7 @@ static int virtblk_probe(struct virtio_device *vdev)
 		set_disk_ro(vblk->disk, 1);
 
 	/* We can handle whatever the host told us to handle. */
-	blk_queue_max_segments(q, vblk->sg_elems-2);
+	blk_queue_max_segments(q, sg_elems);
 
 	/* No real sector limit. */
 	blk_queue_max_hw_sectors(q, -1U);
@@ -925,9 +917,15 @@ static int virtblk_probe(struct virtio_device *vdev)
 
 		virtio_cread(vdev, struct virtio_blk_config, max_discard_seg,
 			     &v);
+
+		/*
+		 * max_discard_seg == 0 is out of spec but we always
+		 * handled it.
+		 */
+		if (!v)
+			v = sg_elems;
 		blk_queue_max_discard_segments(q,
-					       min_not_zero(v,
-							    MAX_DISCARD_SEGMENTS));
+					       min(v, MAX_DISCARD_SEGMENTS));
 
 		blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 	}

drivers/char/virtio_console.c

@@ -1957,6 +1957,13 @@ static void virtcons_remove(struct virtio_device *vdev)
 	list_del(&portdev->list);
 	spin_unlock_irq(&pdrvdata_lock);
 
+	/* Device is going away, exit any polling for buffers */
+	virtio_break_device(vdev);
+	if (use_multiport(portdev))
+		flush_work(&portdev->control_work);
+	else
+		flush_work(&portdev->config_work);
+
 	/* Disable interrupts for vqs */
 	virtio_reset_device(vdev);
 	/* Finish up work that's lined up */

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -1563,11 +1563,27 @@ static virtio_net_ctrl_ack handle_ctrl_mq(struct mlx5_vdpa_dev *mvdev, u8 cmd)
 
 	switch (cmd) {
 	case VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET:
+		/* This mq feature check aligns with pre-existing userspace
+		 * implementation.
+		 *
+		 * Without it, an untrusted driver could fake a multiqueue config
+		 * request down to a non-mq device that may cause kernel to
+		 * panic due to uninitialized resources for extra vqs. Even with
+		 * a well behaving guest driver, it is not expected to allow
+		 * changing the number of vqs on a non-mq device.
+		 */
+		if (!MLX5_FEATURE(mvdev, VIRTIO_NET_F_MQ))
+			break;
+
 		read = vringh_iov_pull_iotlb(&cvq->vring, &cvq->riov, (void *)&mq, sizeof(mq));
 		if (read != sizeof(mq))
 			break;
 
 		newqps = mlx5vdpa16_to_cpu(mvdev, mq.virtqueue_pairs);
+		if (newqps < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN ||
+		    newqps > mlx5_vdpa_max_qps(mvdev->max_vqs))
+			break;
+
 		if (ndev->cur_num_vqs == 2 * newqps) {
 			status = VIRTIO_NET_OK;
 			break;
@@ -1897,11 +1913,25 @@ static u64 mlx5_vdpa_get_device_features(struct vdpa_device *vdev)
 	return ndev->mvdev.mlx_features;
 }
 
-static int verify_min_features(struct mlx5_vdpa_dev *mvdev, u64 features)
+static int verify_driver_features(struct mlx5_vdpa_dev *mvdev, u64 features)
 {
+	/* Minimum features to expect */
 	if (!(features & BIT_ULL(VIRTIO_F_ACCESS_PLATFORM)))
 		return -EOPNOTSUPP;
 
+	/* Double check features combination sent down by the driver.
+	 * Fail invalid features due to absence of the depended feature.
+	 *
+	 * Per VIRTIO v1.1 specification, section 5.1.3.1 Feature bit
+	 * requirements: "VIRTIO_NET_F_MQ Requires VIRTIO_NET_F_CTRL_VQ".
+	 * By failing the invalid features sent down by untrusted drivers,
+	 * we're assured the assumption made upon is_index_valid() and
+	 * is_ctrl_vq_idx() will not be compromised.
+	 */
+	if ((features & (BIT_ULL(VIRTIO_NET_F_MQ) | BIT_ULL(VIRTIO_NET_F_CTRL_VQ))) ==
+            BIT_ULL(VIRTIO_NET_F_MQ))
+		return -EINVAL;
+
 	return 0;
 }
 
@@ -1977,7 +2007,7 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
 
 	print_features(mvdev, features, true);
 
-	err = verify_min_features(mvdev, features);
+	err = verify_driver_features(mvdev, features);
 	if (err)
 		return err;
 

drivers/vdpa/vdpa.c

@@ -393,7 +393,7 @@ static void vdpa_get_config_unlocked(struct vdpa_device *vdev,
 	 * If it does happen we assume a legacy guest.
 	 */
 	if (!vdev->features_valid)
-		vdpa_set_features(vdev, 0, true);
+		vdpa_set_features_unlocked(vdev, 0);
 	ops->get_config(vdev, offset, buf, len);
 }
 

drivers/vdpa/vdpa_user/iova_domain.c

@@ -294,7 +294,7 @@ vduse_domain_alloc_iova(struct iova_domain *iovad,
 
 	iova_pfn = alloc_iova_fast(iovad, iova_len, limit >> shift, true);
 
-	return iova_pfn << shift;
+	return (dma_addr_t)iova_pfn << shift;
 }
 
 static void vduse_domain_free_iova(struct iova_domain *iovad,

drivers/vdpa/virtio_pci/vp_vdpa.c

@@ -533,8 +533,8 @@ static void vp_vdpa_remove(struct pci_dev *pdev)
 {
 	struct vp_vdpa *vp_vdpa = pci_get_drvdata(pdev);
 
-	vdpa_unregister_device(&vp_vdpa->vdpa);
 	vp_modern_remove(&vp_vdpa->mdev);
+	vdpa_unregister_device(&vp_vdpa->vdpa);
 }
 
 static struct pci_driver vp_vdpa_driver = {

drivers/vhost/iotlb.c

@@ -57,6 +57,17 @@ int vhost_iotlb_add_range_ctx(struct vhost_iotlb *iotlb,
 	if (last < start)
 		return -EFAULT;
 
+	/* If the range being mapped is [0, ULONG_MAX], split it into two entries
+	 * otherwise its size would overflow u64.
+	 */
+	if (start == 0 && last == ULONG_MAX) {
+		u64 mid = last / 2;
+
+		vhost_iotlb_add_range_ctx(iotlb, start, mid, addr, perm, opaque);
+		addr += mid + 1;
+		start = mid + 1;
+	}
+
 	if (iotlb->limit &&
 	    iotlb->nmaps == iotlb->limit &&
 	    iotlb->flags & VHOST_IOTLB_FLAG_RETIRE) {

drivers/vhost/vdpa.c

@@ -286,7 +286,7 @@ static long vhost_vdpa_set_features(struct vhost_vdpa *v, u64 __user *featurep)
 	if (copy_from_user(&features, featurep, sizeof(features)))
 		return -EFAULT;
 
-	if (vdpa_set_features(vdpa, features, false))
+	if (vdpa_set_features(vdpa, features))
 		return -EINVAL;
 
 	return 0;

drivers/vhost/vhost.c

@@ -1170,6 +1170,11 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
 		goto done;
 	}
 
+	if (msg.size == 0) {
+		ret = -EINVAL;
+		goto done;
+	}
+
 	if (dev->msg_handler)
 		ret = dev->msg_handler(dev, &msg);
 	else
@@ -1981,7 +1986,7 @@ static int vhost_update_used_flags(struct vhost_virtqueue *vq)
 	return 0;
 }
 
-static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
+static int vhost_update_avail_event(struct vhost_virtqueue *vq)
 {
 	if (vhost_put_avail_event(vq))
 		return -EFAULT;
@@ -2527,7 +2532,7 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 			return false;
 		}
 	} else {
-		r = vhost_update_avail_event(vq, vq->avail_idx);
+		r = vhost_update_avail_event(vq);
 		if (r) {
 			vq_err(vq, "Failed to update avail event index at %p: %d\n",
 			       vhost_avail_event(vq), r);

drivers/virtio/Kconfig

@@ -105,7 +105,6 @@ config VIRTIO_BALLOON
 
 config VIRTIO_MEM
 	tristate "Virtio mem driver"
-	default m
 	depends on X86_64
 	depends on VIRTIO
 	depends on MEMORY_HOTPLUG

drivers/virtio/virtio.c

@@ -166,14 +166,13 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status)
 }
 EXPORT_SYMBOL_GPL(virtio_add_status);
 
-int virtio_finalize_features(struct virtio_device *dev)
+/* Do some validation, then set FEATURES_OK */
+static int virtio_features_ok(struct virtio_device *dev)
 {
-	int ret = dev->config->finalize_features(dev);
 	unsigned status;
+	int ret;
 
 	might_sleep();
-	if (ret)
-		return ret;
 
 	ret = arch_has_restricted_virtio_memory_access();
 	if (ret) {
@@ -202,8 +201,23 @@ int virtio_finalize_features(struct virtio_device *dev)
 	}
 	return 0;
 }
-EXPORT_SYMBOL_GPL(virtio_finalize_features);
 
+/**
+ * virtio_reset_device - quiesce device for removal
+ * @dev: the device to reset
+ *
+ * Prevents device from sending interrupts and accessing memory.
+ *
+ * Generally used for cleanup during driver / device removal.
+ *
+ * Once this has been invoked, caller must ensure that
+ * virtqueue_notify / virtqueue_kick are not in progress.
+ *
+ * Note: this guarantees that vq callbacks are not in progress, however caller
+ * is responsible for preventing access from other contexts, such as a system
+ * call/workqueue/bh.  Invoking virtio_break_device then flushing any such
+ * contexts is one way to handle that.
+ * */
 void virtio_reset_device(struct virtio_device *dev)
 {
 	dev->config->reset(dev);
@@ -245,17 +259,6 @@ static int virtio_dev_probe(struct device *_d)
 		driver_features_legacy = driver_features;
 	}
 
-	/*
-	 * Some devices detect legacy solely via F_VERSION_1. Write
-	 * F_VERSION_1 to force LE config space accesses before FEATURES_OK for
-	 * these when needed.
-	 */
-	if (drv->validate && !virtio_legacy_is_little_endian()
-			  && device_features & BIT_ULL(VIRTIO_F_VERSION_1)) {
-		dev->features = BIT_ULL(VIRTIO_F_VERSION_1);
-		dev->config->finalize_features(dev);
-	}
-
 	if (device_features & (1ULL << VIRTIO_F_VERSION_1))
 		dev->features = driver_features & device_features;
 	else
@@ -266,13 +269,26 @@ static int virtio_dev_probe(struct device *_d)
 		if (device_features & (1ULL << i))
 			__virtio_set_bit(dev, i);
 
+	err = dev->config->finalize_features(dev);
+	if (err)
+		goto err;
+
 	if (drv->validate) {
+		u64 features = dev->features;
+
 		err = drv->validate(dev);
 		if (err)
 			goto err;
+
+		/* Did validation change any features? Then write them again. */
+		if (features != dev->features) {
+			err = dev->config->finalize_features(dev);
+			if (err)
+				goto err;
+		}
 	}
 
-	err = virtio_finalize_features(dev);
+	err = virtio_features_ok(dev);
 	if (err)
 		goto err;
 
@@ -496,7 +512,11 @@ int virtio_device_restore(struct virtio_device *dev)
 	/* We have a driver! */
 	virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
 
-	ret = virtio_finalize_features(dev);
+	ret = dev->config->finalize_features(dev);
+	if (ret)
+		goto err;
+
+	ret = virtio_features_ok(dev);
 	if (ret)
 		goto err;
 

drivers/virtio/virtio_vdpa.c

@@ -317,7 +317,7 @@ static int virtio_vdpa_finalize_features(struct virtio_device *vdev)
 	/* Give virtio_ring a chance to accept features. */
 	vring_transport_features(vdev);
 
-	return vdpa_set_features(vdpa, vdev->features, false);
+	return vdpa_set_features(vdpa, vdev->features);
 }
 
 static const char *virtio_vdpa_bus_name(struct virtio_device *vdev)

include/linux/vdpa.h

@@ -401,18 +401,24 @@ static inline int vdpa_reset(struct vdpa_device *vdev)
 	return ret;
 }
 
-static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features, bool locked)
+static inline int vdpa_set_features_unlocked(struct vdpa_device *vdev, u64 features)
 {
 	const struct vdpa_config_ops *ops = vdev->config;
 	int ret;
 
-	if (!locked)
-		mutex_lock(&vdev->cf_mutex);
-
 	vdev->features_valid = true;
 	ret = ops->set_driver_features(vdev, features);
-	if (!locked)
-		mutex_unlock(&vdev->cf_mutex);
+
+	return ret;
+}
+
+static inline int vdpa_set_features(struct vdpa_device *vdev, u64 features)
+{
+	int ret;
+
+	mutex_lock(&vdev->cf_mutex);
+	ret = vdpa_set_features_unlocked(vdev, features);
+	mutex_unlock(&vdev->cf_mutex);
 
 	return ret;
 }

include/linux/virtio.h

@@ -133,7 +133,6 @@ bool is_virtio_device(struct device *dev);
 void virtio_break_device(struct virtio_device *dev);
 
 void virtio_config_changed(struct virtio_device *dev);
-int virtio_finalize_features(struct virtio_device *dev);
 #ifdef CONFIG_PM_SLEEP
 int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);

include/linux/virtio_config.h

@@ -64,8 +64,9 @@ struct virtio_shm_region {
  *	Returns the first 64 feature bits (all we currently need).
  * @finalize_features: confirm what device features we'll be using.
  *	vdev: the virtio_device
- *	This gives the final feature bits for the device: it can change
+ *	This sends the driver feature bits to the device: it can change
  *	the dev->feature bits if it wants.
+ * Note: despite the name this can be called any number of times.
  *	Returns 0 on success or error status
  * @bus_name: return the bus name associated with the device (optional)
  *	vdev: the virtio_device

tools/virtio/linux/mm_types.h

@@ -0,0 +1,3 @@
+struct folio {
+       struct page page;
+};

tools/virtio/virtio_test.c

@@ -130,6 +130,7 @@ static void vdev_info_init(struct vdev_info* dev, unsigned long long features)
 	memset(dev, 0, sizeof *dev);
 	dev->vdev.features = features;
 	INIT_LIST_HEAD(&dev->vdev.vqs);
+	spin_lock_init(&dev->vdev.vqs_list_lock);
 	dev->buf_size = 1024;
 	dev->buf = malloc(dev->buf_size);
 	assert(dev->buf);