Patch "virtio: Protect vqs list access" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    virtio: Protect vqs list access

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     virtio-protect-vqs-list-access.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit ec7c95e32fa39841854ad14149368a7a80ee74a7
Author: Parav Pandit <parav@xxxxxxxxxx>
Date:   Wed Jul 21 17:26:47 2021 +0300

    virtio: Protect vqs list access
    
    [ Upstream commit 0e566c8f0f2e8325e35f6f97e13cde5356b41814 ]
    
    VQs may be accessed to mark the device broken while they are
    created/destroyed. Hence protect the access to the vqs list.
    
    Fixes: e2dcdfe95c0b ("virtio: virtio_break_device() to mark all virtqueues broken.")
    Signed-off-by: Parav Pandit <parav@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20210721142648.1525924-4-parav@xxxxxxxxxx
    Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index a977e32a88f2..59a05f1b8105 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -342,6 +342,7 @@ int register_virtio_device(struct virtio_device *dev)
 	virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
 
 	INIT_LIST_HEAD(&dev->vqs);
+	spin_lock_init(&dev->vqs_list_lock);
 
 	/*
 	 * device_add() causes the bus infrastructure to look for a matching
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 97e8a195e18f..f6011c9ed32f 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1668,7 +1668,9 @@ static struct virtqueue *vring_create_virtqueue_packed(
 			cpu_to_le16(vq->packed.event_flags_shadow);
 	}
 
+	spin_lock(&vdev->vqs_list_lock);
 	list_add_tail(&vq->vq.list, &vdev->vqs);
+	spin_unlock(&vdev->vqs_list_lock);
 	return &vq->vq;
 
 err_desc_extra:
@@ -2126,7 +2128,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index,
 	memset(vq->split.desc_state, 0, vring.num *
 			sizeof(struct vring_desc_state_split));
 
+	spin_lock(&vdev->vqs_list_lock);
 	list_add_tail(&vq->vq.list, &vdev->vqs);
+	spin_unlock(&vdev->vqs_list_lock);
 	return &vq->vq;
 }
 EXPORT_SYMBOL_GPL(__vring_new_virtqueue);
@@ -2210,7 +2214,9 @@ void vring_del_virtqueue(struct virtqueue *_vq)
 	}
 	if (!vq->packed_ring)
 		kfree(vq->split.desc_state);
+	spin_lock(&vq->vq.vdev->vqs_list_lock);
 	list_del(&_vq->list);
+	spin_unlock(&vq->vq.vdev->vqs_list_lock);
 	kfree(vq);
 }
 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
@@ -2274,10 +2280,12 @@ void virtio_break_device(struct virtio_device *dev)
 {
 	struct virtqueue *_vq;
 
+	spin_lock(&dev->vqs_list_lock);
 	list_for_each_entry(_vq, &dev->vqs, list) {
 		struct vring_virtqueue *vq = to_vvq(_vq);
 		vq->broken = true;
 	}
+	spin_unlock(&dev->vqs_list_lock);
 }
 EXPORT_SYMBOL_GPL(virtio_break_device);
 
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 15f906e4a748..7c075463c7f2 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -111,6 +111,7 @@ struct virtio_device {
 	bool config_enabled;
 	bool config_change_pending;
 	spinlock_t config_lock;
+	spinlock_t vqs_list_lock; /* Protects VQs list access */
 	struct device dev;
 	struct virtio_device_id id;
 	const struct virtio_config_ops *config;