media: pci: ivtv: Add check for DMA map result

In case DMA fails, 'dma->SG_length' is 0. This value is later used to
access 'dma->SGarray[dma->SG_length - 1]', which will cause out of
bounds access.

Add check to return early on invalid value. Adjust warnings accordingly.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 1932dc2f ("media: pci/ivtv: switch from 'pci_' to 'dma_' API")
Signed-off-by: Mikhail Kobuk <m.kobuk@ispras.ru>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/pci/ivtv/ivtv-udma.c

@@ -131,6 +131,8 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
 
 	/* Fill SG List with new values */
 	if (ivtv_udma_fill_sg_list(dma, &user_dma, 0) < 0) {
+		IVTV_DEBUG_WARN("%s: could not allocate bounce buffers for highmem userspace buffers\n",
+				__func__);
 		unpin_user_pages(dma->map, dma->page_count);
 		dma->page_count = 0;
 		return -ENOMEM;
@@ -139,6 +141,12 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
 	/* Map SG List */
 	dma->SG_length = dma_map_sg(&itv->pdev->dev, dma->SGlist,
 				    dma->page_count, DMA_TO_DEVICE);
+	if (!dma->SG_length) {
+		IVTV_DEBUG_WARN("%s: DMA map error, SG_length is 0\n", __func__);
+		unpin_user_pages(dma->map, dma->page_count);
+		dma->page_count = 0;
+		return -EINVAL;
+	}
 
 	/* Fill SG Array with new values */
 	ivtv_udma_fill_sg_array (dma, ivtv_dest_addr, 0, -1);

drivers/media/pci/ivtv/ivtv-yuv.c

@@ -114,6 +114,12 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
 	}
 	dma->SG_length = dma_map_sg(&itv->pdev->dev, dma->SGlist,
 				    dma->page_count, DMA_TO_DEVICE);
+	if (!dma->SG_length) {
+		IVTV_DEBUG_WARN("%s: DMA map error, SG_length is 0\n", __func__);
+		unpin_user_pages(dma->map, dma->page_count);
+		dma->page_count = 0;
+		return -EINVAL;
+	}
 
 	/* Fill SG Array with new values */
 	ivtv_udma_fill_sg_array(dma, y_buffer_offset, uv_buffer_offset, y_size);

drivers/media/pci/ivtv/ivtvfb.c

@@ -281,10 +281,10 @@ static int ivtvfb_prep_dec_dma_to_device(struct ivtv *itv,
 	/* Map User DMA */
 	if (ivtv_udma_setup(itv, ivtv_dest_addr, userbuf, size_in_bytes) <= 0) {
 		mutex_unlock(&itv->udma.lock);
-		IVTVFB_WARN("ivtvfb_prep_dec_dma_to_device, Error with pin_user_pages: %d bytes, %d pages returned\n",
-			       size_in_bytes, itv->udma.page_count);
+		IVTVFB_WARN("%s, Error in ivtv_udma_setup: %d bytes, %d pages returned\n",
+			       __func__, size_in_bytes, itv->udma.page_count);
 
-		/* pin_user_pages must have failed completely */
+		/* pin_user_pages or DMA must have failed completely */
 		return -EIO;
 	}