vhost: Distinguish errors in vhost_dev_get_config()

Instead of just returning 0/-1 and letting the caller make up a
meaningless error message, add an Error parameter to allow reporting the
real error and switch to 0/-errno so that different kind of errors can
be distinguished in the caller.

config_len in vhost_user_get_config() is defined by the device, so if
it's larger than VHOST_USER_MAX_CONFIG_SIZE, this is a programming
error. Turn the corresponding check into an assertion.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20210609154658.350308-6-kwolf@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

4 files changed, 29 insertions, 20 deletions

diff --git a/hw/virtio/vhost-user-vsock.c b/hw/virtio/vhost-user-vsock.c
index b6a4a25ea1..6095ed7349 100644
--- a/hw/virtio/vhost-user-vsock.c
+++ b/hw/virtio/vhost-user-vsock.c
@@ -34,10 +34,12 @@ static void vuv_get_config(VirtIODevice *vdev, uint8_t *config)
 static int vuv_handle_config_change(struct vhost_dev *dev)
 {
     VHostUserVSock *vsock = VHOST_USER_VSOCK(dev->vdev);
+    Error *local_err = NULL;
     int ret = vhost_dev_get_config(dev, (uint8_t *)&vsock->vsockcfg,
-                                   sizeof(struct virtio_vsock_config));
+                                   sizeof(struct virtio_vsock_config),
+                                   &local_err);
     if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
         return -1;
     }
 
@@ -114,9 +116,8 @@ static void vuv_device_realize(DeviceState *dev, Error **errp)
     }
 
     ret = vhost_dev_get_config(&vvc->vhost_dev, (uint8_t *)&vsock->vsockcfg,
-                               sizeof(struct virtio_vsock_config));
+                               sizeof(struct virtio_vsock_config), errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "get config space failed");
         goto err_vhost_dev;
     }
 
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 889559d86a..1ac4a2ebec 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2117,7 +2117,7 @@ static void vhost_user_set_iotlb_callback(struct vhost_dev *dev, int enabled)
 }
 
 static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
-                                 uint32_t config_len)
+                                 uint32_t config_len, Error **errp)
 {
     VhostUserMsg msg = {
         .hdr.request = VHOST_USER_GET_CONFIG,
@@ -2127,32 +2127,32 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
 
     if (!virtio_has_feature(dev->protocol_features,
                 VHOST_USER_PROTOCOL_F_CONFIG)) {
-        return -1;
+        error_setg(errp, "VHOST_USER_PROTOCOL_F_CONFIG not supported");
+        return -EINVAL;
     }
 
-    if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
-        return -1;
-    }
+    assert(config_len <= VHOST_USER_MAX_CONFIG_SIZE);
 
     msg.payload.config.offset = 0;
     msg.payload.config.size = config_len;
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     if (vhost_user_read(dev, &msg) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     if (msg.hdr.request != VHOST_USER_GET_CONFIG) {
-        error_report("Received unexpected msg type. Expected %d received %d",
-                     VHOST_USER_GET_CONFIG, msg.hdr.request);
-        return -1;
+        error_setg(errp,
+                   "Received unexpected msg type. Expected %d received %d",
+                   VHOST_USER_GET_CONFIG, msg.hdr.request);
+        return -EINVAL;
     }
 
     if (msg.hdr.size != VHOST_USER_CONFIG_HDR_SIZE + config_len) {
-        error_report("Received bad msg size.");
-        return -1;
+        error_setg(errp, "Received bad msg size.");
+        return -EINVAL;
     }
 
     memcpy(config, msg.payload.config.region, config_len);
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 0f469f1823..4fa414feea 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -523,7 +523,7 @@ static int vhost_vdpa_set_config(struct vhost_dev *dev, const uint8_t *data,
 }
 
 static int vhost_vdpa_get_config(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len)
+                                   uint32_t config_len, Error **errp)
 {
     struct vhost_vdpa_config *v_config;
     unsigned long config_size = offsetof(struct vhost_vdpa_config, buf);
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index c7f9d8bb06..e8f85a5d2d 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1562,15 +1562,23 @@ void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
 }
 
 int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
-                         uint32_t config_len)
+                         uint32_t config_len, Error **errp)
 {
+    ERRP_GUARD();
+    int ret;
+
     assert(hdev->vhost_ops);
 
     if (hdev->vhost_ops->vhost_get_config) {
-        return hdev->vhost_ops->vhost_get_config(hdev, config, config_len);
+        ret = hdev->vhost_ops->vhost_get_config(hdev, config, config_len, errp);
+        if (ret < 0 && !*errp) {
+            error_setg_errno(errp, -ret, "vhost_get_config failed");
+        }
+        return ret;
     }
 
-    return -1;
+    error_setg(errp, "vhost_get_config not implemented");
+    return -ENOTSUP;
 }
 
 int vhost_dev_set_config(struct vhost_dev *hdev, const uint8_t *data,