samples: vfio-mdev: fix error handing in mdpy_fb_probe()

Fix to return a negative error code from the framebuffer_alloc() error
handling case instead of 0, also release regions in some error handing
cases.

Fixes: cacade19 ("sample: vfio mdev display - guest driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Message-Id: <20210520133641.1421378-1-weiyongjun1@huawei.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

samples/vfio-mdev/mdpy-fb.c

@@ -117,22 +117,27 @@ static int mdpy_fb_probe(struct pci_dev *pdev,
 	if (format != DRM_FORMAT_XRGB8888) {
 		pci_err(pdev, "format mismatch (0x%x != 0x%x)\n",
 			format, DRM_FORMAT_XRGB8888);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto err_release_regions;
 	}
 	if (width < 100	 || width > 10000) {
 		pci_err(pdev, "width (%d) out of range\n", width);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto err_release_regions;
 	}
 	if (height < 100 || height > 10000) {
 		pci_err(pdev, "height (%d) out of range\n", height);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto err_release_regions;
 	}
 	pci_info(pdev, "mdpy found: %dx%d framebuffer\n",
 		 width, height);
 
 	info = framebuffer_alloc(sizeof(struct mdpy_fb_par), &pdev->dev);
-	if (!info)
+	if (!info) {
+		ret = -ENOMEM;
 		goto err_release_regions;
+	}
 	pci_set_drvdata(pdev, info);
 	par = info->par;