vdpa: Read device configuration only if FEATURES_OK

Avoid reading device configuration during feature negotiation. Read
device status and verify that VIRTIO_CONFIG_S_FEATURES_OK is set.

Protect the entire operation, including configuration read with cf_mutex
to ensure integrity of the results.

Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220105114646.577224-5-elic@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 5134c83..4494325 100644 (file)
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -393,6 +393,21 @@ void vdpa_mgmtdev_unregister(struct vdpa_mgmt_dev *mdev)
 }
 EXPORT_SYMBOL_GPL(vdpa_mgmtdev_unregister);
 
+static void vdpa_get_config_unlocked(struct vdpa_device *vdev,
+                                    unsigned int offset,
+                                    void *buf, unsigned int len)
+{
+       const struct vdpa_config_ops *ops = vdev->config;
+
+       /*
+        * Config accesses aren't supposed to trigger before features are set.
+        * If it does happen we assume a legacy guest.
+        */
+       if (!vdev->features_valid)
+               vdpa_set_features(vdev, 0);
+       ops->get_config(vdev, offset, buf, len);
+}
+
 /**
  * vdpa_get_config - Get one or more device configuration fields.
  * @vdev: vdpa device to operate on
@@ -403,16 +418,8 @@ EXPORT_SYMBOL_GPL(vdpa_mgmtdev_unregister);
 void vdpa_get_config(struct vdpa_device *vdev, unsigned int offset,
                     void *buf, unsigned int len)
 {
-       const struct vdpa_config_ops *ops = vdev->config;
-
        mutex_lock(&vdev->cf_mutex);
-       /*
-        * Config accesses aren't supposed to trigger before features are set.
-        * If it does happen we assume a legacy guest.
-        */
-       if (!vdev->features_valid)
-               vdpa_set_features(vdev, 0);
-       ops->get_config(vdev, offset, buf, len);
+       vdpa_get_config_unlocked(vdev, offset, buf, len);
        mutex_unlock(&vdev->cf_mutex);
 }
 EXPORT_SYMBOL_GPL(vdpa_get_config);
@@ -813,7 +820,7 @@ static int vdpa_dev_net_config_fill(struct vdpa_device *vdev, struct sk_buff *ms
        u64 features;
        u16 val_u16;
 
-       vdpa_get_config(vdev, 0, &config, sizeof(config));
+       vdpa_get_config_unlocked(vdev, 0, &config, sizeof(config));
 
        if (nla_put(msg, VDPA_ATTR_DEV_NET_CFG_MACADDR, sizeof(config.mac),
                    config.mac))
@@ -838,12 +845,23 @@ vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid,
 {
        u32 device_id;
        void *hdr;
+       u8 status;
        int err;
 
+       mutex_lock(&vdev->cf_mutex);
+       status = vdev->config->get_status(vdev);
+       if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
+               NL_SET_ERR_MSG_MOD(extack, "Features negotiation not completed");
+               err = -EAGAIN;
+               goto out;
+       }
+
        hdr = genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags,
                          VDPA_CMD_DEV_CONFIG_GET);
-       if (!hdr)
-               return -EMSGSIZE;
+       if (!hdr) {
+               err = -EMSGSIZE;
+               goto out;
+       }
 
        if (nla_put_string(msg, VDPA_ATTR_DEV_NAME, dev_name(&vdev->dev))) {
                err = -EMSGSIZE;
@@ -867,11 +885,14 @@ vdpa_dev_config_fill(struct vdpa_device *vdev, struct sk_buff *msg, u32 portid,
        if (err)
                goto msg_err;
 
+       mutex_unlock(&vdev->cf_mutex);
        genlmsg_end(msg, hdr);
        return 0;
 
 msg_err:
        genlmsg_cancel(msg, hdr);
+out:
+       mutex_unlock(&vdev->cf_mutex);
        return err;
 }