V4L/DVB (13239): saa7146: fix memory leakage in pagetable-handling

In buffer_release() the previously allocated pagetables are not
freed,  which might result in a memory leak in certain application
use-cases, where the frame format is changed from planar format to
non-planar format. The fix explicitely frees the page tables when a
format change is done and when buffer_release() is called.
Signed-off-by: Johann Friedrichs <johann.friedrichs@web.de>
Signed-off-by: Michael Hunold <hunold@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/common/saa7146_video.c

@@ -1205,6 +1205,13 @@ static int buffer_activate (struct saa7146_dev *dev,
 	return 0;
 }
 
+static void release_all_pagetables(struct saa7146_dev *dev, struct saa7146_buf *buf)
+{
+	saa7146_pgtable_free(dev->pci, &buf->pt[0]);
+	saa7146_pgtable_free(dev->pci, &buf->pt[1]);
+	saa7146_pgtable_free(dev->pci, &buf->pt[2]);
+}
+
 static int buffer_prepare(struct videobuf_queue *q,
 			  struct videobuf_buffer *vb, enum v4l2_field field)
 {
@@ -1257,16 +1264,12 @@ static int buffer_prepare(struct videobuf_queue *q,
 
 		sfmt = format_by_fourcc(dev,buf->fmt->pixelformat);
 
+		release_all_pagetables(dev, buf);
 		if( 0 != IS_PLANAR(sfmt->trans)) {
-			saa7146_pgtable_free(dev->pci, &buf->pt[0]);
-			saa7146_pgtable_free(dev->pci, &buf->pt[1]);
-			saa7146_pgtable_free(dev->pci, &buf->pt[2]);
-
 			saa7146_pgtable_alloc(dev->pci, &buf->pt[0]);
 			saa7146_pgtable_alloc(dev->pci, &buf->pt[1]);
 			saa7146_pgtable_alloc(dev->pci, &buf->pt[2]);
 		} else {
-			saa7146_pgtable_free(dev->pci, &buf->pt[0]);
 			saa7146_pgtable_alloc(dev->pci, &buf->pt[0]);
 		}
 
@@ -1329,6 +1332,9 @@ static void buffer_release(struct videobuf_queue *q, struct videobuf_buffer *vb)
 	struct saa7146_buf *buf = (struct saa7146_buf *)vb;
 
 	DEB_CAP(("vbuf:%p\n",vb));
+
+	release_all_pagetables(dev, buf);
+
 	saa7146_dma_free(dev,q,buf);
 }