staging: kpc2000: kpc_dma: Unpin partial pinned pages

There is a bug, when get_user_pages() failed but partially pinned
pages are not unpinned and positive numbers are returned instead of
-ERRNO. Fixed it.

Also, int is more appropriate type for rv. Changed it.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Bharath Vedartham <linux.bhar@gmail.com>
Link: https://lore.kernel.org/r/1593584264-16982-2-git-send-email-jrdr.linux@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/kpc2000/kpc_dma/fileops.c

@@ -35,7 +35,7 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 			    unsigned long iov_base, size_t iov_len)
 {
 	unsigned int i = 0;
-	long rv = 0;
+	int rv = 0;
 	struct kpc_dma_device *ldev;
 	struct aio_cb_data *acd;
 	DECLARE_COMPLETION_ONSTACK(done);
@@ -79,14 +79,14 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 	rv = get_user_pages(iov_base, acd->page_count, FOLL_TOUCH | FOLL_WRITE | FOLL_GET, acd->user_pages, NULL);
 	mmap_read_unlock(current->mm);        /*  release the semaphore */
 	if (rv != acd->page_count) {
-		dev_err(&priv->ldev->pldev->dev, "Couldn't get_user_pages (%ld)\n", rv);
+		dev_err(&priv->ldev->pldev->dev, "Couldn't get_user_pages (%d)\n", rv);
 		goto err_get_user_pages;
 	}
 
 	// Allocate and setup the sg_table (scatterlist entries)
 	rv = sg_alloc_table_from_pages(&acd->sgt, acd->user_pages, acd->page_count, iov_base & (PAGE_SIZE - 1), iov_len, GFP_KERNEL);
 	if (rv) {
-		dev_err(&priv->ldev->pldev->dev, "Couldn't alloc sg_table (%ld)\n", rv);
+		dev_err(&priv->ldev->pldev->dev, "Couldn't alloc sg_table (%d)\n", rv);
 		goto err_alloc_sg_table;
 	}
 
@@ -193,10 +193,15 @@ static int kpc_dma_transfer(struct dev_private_data *priv,
 		put_page(acd->user_pages[i]);
 
  err_get_user_pages:
+	if (rv > 0) {
+		for (i = 0; i < rv; i++)
+			put_pages(acd->user_pages[i]);
+		rv = -EFAULT;
+	}
 	kfree(acd->user_pages);
  err_alloc_userpages:
 	kfree(acd);
-	dev_dbg(&priv->ldev->pldev->dev, "%s returning with error %ld\n", __func__, rv);
+	dev_dbg(&priv->ldev->pldev->dev, "%s returning with error %d\n", __func__, rv);
 	return rv;
 }