[media] media: videobuf2: fix the length check for mmap

Memory maps typically require that the buffer size to be page
aligned. Currently, two memops drivers do such alignment
internally, but videobuf-vmalloc doesn't.
Also, the buffer overflow check doesn't take it into account.
So, instead of doing it at each memops driver, enforce it at
VB2 core.
Reported-by: Prabhakar lad <prabhakar.csengg@gmail.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/v4l2-core/videobuf2-core.c

@@ -54,10 +54,15 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
 	void *mem_priv;
 	int plane;
 
-	/* Allocate memory for all planes in this buffer */
+	/*
+	 * Allocate memory for all planes in this buffer
+	 * NOTE: mmapped areas should be page aligned
+	 */
 	for (plane = 0; plane < vb->num_planes; ++plane) {
+		unsigned long size = PAGE_ALIGN(q->plane_sizes[plane]);
+
 		mem_priv = call_memop(q, alloc, q->alloc_ctx[plane],
-				      q->plane_sizes[plane], q->gfp_flags);
+				      size, q->gfp_flags);
 		if (IS_ERR_OR_NULL(mem_priv))
 			goto free;
 
@@ -1852,6 +1857,7 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
 	struct vb2_buffer *vb;
 	unsigned int buffer, plane;
 	int ret;
+	unsigned long length;
 
 	if (q->memory != V4L2_MEMORY_MMAP) {
 		dprintk(1, "Queue is not currently set up for mmap\n");
@@ -1886,8 +1892,15 @@ int vb2_mmap(struct vb2_queue *q, struct vm_area_struct *vma)
 
 	vb = q->bufs[buffer];
 
-	if (vb->v4l2_planes[plane].length < (vma->vm_end - vma->vm_start)) {
-		dprintk(1, "Invalid length\n");
+	/*
+	 * MMAP requires page_aligned buffers.
+	 * The buffer length was page_aligned at __vb2_buf_mem_alloc(),
+	 * so, we need to do the same here.
+	 */
+	length = PAGE_ALIGN(vb->v4l2_planes[plane].length);
+	if (length < (vma->vm_end - vma->vm_start)) {
+		dprintk(1,
+			"MMAP invalid, as it would overflow buffer length\n");
 		return -EINVAL;
 	}
 

drivers/media/v4l2-core/videobuf2-dma-contig.c

@@ -162,9 +162,6 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size, gfp_t gfp_flags)
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
-	/* align image size to PAGE_SIZE */
-	size = PAGE_ALIGN(size);
-
 	buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr,
 						GFP_KERNEL | gfp_flags);
 	if (!buf->vaddr) {

drivers/media/v4l2-core/videobuf2-dma-sg.c

@@ -55,7 +55,8 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size, gfp_t gfp_fla
 	buf->write = 0;
 	buf->offset = 0;
 	buf->sg_desc.size = size;
-	buf->sg_desc.num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	/* size is already page aligned */
+	buf->sg_desc.num_pages = size >> PAGE_SHIFT;
 
 	buf->sg_desc.sglist = vzalloc(buf->sg_desc.num_pages *
 				      sizeof(*buf->sg_desc.sglist));