V4L/DVB: v4l: videobuf: prevent passing a NULL to dma_free_coherent()

When a driver that uses videobuf-dma-contig is used with the USERPTR
memory access method a kernel oops might happen: a NULL address may be
passed to dma_free_coherent(). This happens when an application calls
REQBUFS and then exits without queuing any buffers. This patch fixes
that bug.

Signed-off-by: Pawel Osciak <p.osciak@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/media/video/videobuf-dma-contig.c b/drivers/media/video/videobuf-dma-contig.c
index 372b87e..6ff9e4b 100644 (file)
--- a/drivers/media/video/videobuf-dma-contig.c
+++ b/drivers/media/video/videobuf-dma-contig.c
@@ -393,8 +393,10 @@ void videobuf_dma_contig_free(struct videobuf_queue *q,
        }
 
        /* read() method */
-       dma_free_coherent(q->dev, mem->size, mem->vaddr, mem->dma_handle);
-       mem->vaddr = NULL;
+       if (mem->vaddr) {
+               dma_free_coherent(q->dev, mem->size, mem->vaddr, mem->dma_handle);
+               mem->vaddr = NULL;
+       }
 }
 EXPORT_SYMBOL_GPL(videobuf_dma_contig_free);