media: videobuf2: Fix IS_ERR checking in vb2_dc_put_userptr()

In order to avoid error pointers from frame_vector_pages(), we could
use IS_ERR() to check the return value to fix this. This checking
operation could make sure that vector contains pages.

Signed-off-by: Ma Ke <make_ruc2021@163.com>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Author: Ma Ke

drivers/media/common/videobuf2/videobuf2-dma-contig.c

@@ -542,13 +542,14 @@ static void vb2_dc_put_userptr(void *buf_priv)
 		 */
 		dma_unmap_sgtable(buf->dev, sgt, buf->dma_dir,
 				  DMA_ATTR_SKIP_CPU_SYNC);
-		pages = frame_vector_pages(buf->vec);
-		/* sgt should exist only if vector contains pages... */
-		BUG_ON(IS_ERR(pages));
 		if (buf->dma_dir == DMA_FROM_DEVICE ||
-		    buf->dma_dir == DMA_BIDIRECTIONAL)
-			for (i = 0; i < frame_vector_count(buf->vec); i++)
-				set_page_dirty_lock(pages[i]);
+				buf->dma_dir == DMA_BIDIRECTIONAL) {
+			pages = frame_vector_pages(buf->vec);
+			/* sgt should exist only if vector contains pages... */
+			if (!WARN_ON_ONCE(IS_ERR(pages)))
+				for (i = 0; i < frame_vector_count(buf->vec); i++)
+					set_page_dirty_lock(pages[i]);
+		}
 		sg_free_table(sgt);
 		kfree(sgt);
 	} else {