[PATCH] media: omap_vout: potential buffer overflow in vidioc_dqbuf()

[Dan Carpenter <dan.carpenter@oracle.com>]

The "b->index" is a u32 the comes from the user in the ioctl.  It hasn't
been checked.  We aren't supposed to use it but we're instead supposed
to use the value that gets written to it when we call videobuf_dqbuf().

The videobuf_dqbuf() first memsets it to zero and then re-initializes it
inside the videobuf_status() function.  It's this final value which we
want.

Fixes: 72915e851da9 ("[media] V4L2: OMAP: VOUT: dma map and unmap v4l2 buffers in qbuf and dqbuf")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
UNTESTED!  I think I understand this code now, but I have struggled to
read it correctly in the past.  Please review carefully.


 drivers/media/platform/omap/omap_vout.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/omap/omap_vout.c b/drivers/media/platform/omap/omap_vout.c
index 37f0d7146dfa..15e38990e85a 100644
--- a/drivers/media/platform/omap/omap_vout.c
+++ b/drivers/media/platform/omap/omap_vout.c
@@ -1527,8 +1527,6 @@ static int vidioc_dqbuf(struct file *file, void *fh, struct v4l2_buffer *b)
 	unsigned long size;
 	struct videobuf_buffer *vb;
 
-	vb = q->bufs[b->index];
-
 	if (!vout->streaming)
 		return -EINVAL;
 
@@ -1539,6 +1537,8 @@ static int vidioc_dqbuf(struct file *file, void *fh, struct v4l2_buffer *b)
 		/* Call videobuf_dqbuf for  blocking mode */
 		ret = videobuf_dqbuf(q, (struct v4l2_buffer *)b, 0);
 
+	vb = q->bufs[b->index];
+
 	addr = (unsigned long) vout->buf_phy_addr[vb->i];
 	size = (unsigned long) vb->size;
 	dma_unmap_single(vout->vid_dev->v4l2_dev.dev,  addr,
-- 
2.17.1