[PATCHv4 for v3.17] v4l2-ioctl: don't set PRIV_MAGIC unconditionally in g_fmt()

[Hans Verkuil <hverkuil@xs4all.nl>]

Regression fix:

V4L2_PIX_FMT_PRIV_MAGIC should only be set for the VIDEO_CAPTURE and
VIDEO_OUTPUT buffer types, and not for any others. In the case of
the win format this overwrote a pointer value that is passed in from
userspace.

Just set it for V4L2_BUF_TYPE_VIDEO_CAPTURE and OUTPUT only. Set
it before the callback is called, just as is done for try/s_fmt, and
again afterwards in case the driver zeroed it. The latter was missing
in try/s_fmt, so add it there as well. Currently it is quite likely
that drivers clear priv (that was needed for a long time), so it makes
sense to set it twice.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>

diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
index e620387..9fc8076 100644
--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -1143,8 +1143,6 @@ static int v4l_g_fmt(const struct v4l2_ioctl_ops *ops,
 	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
 	int ret;
 
-	p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
-
 	/*
 	 * fmt can't be cleared for these overlay types due to the 'clips'
 	 * 'clipcount' and 'bitmap' pointers in struct v4l2_window.
@@ -1173,7 +1171,9 @@ static int v4l_g_fmt(const struct v4l2_ioctl_ops *ops,
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_g_fmt_vid_cap))
 			break;
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
 		ret = ops->vidioc_g_fmt_vid_cap(file, fh, arg);
+		/* just in case the driver zeroed it again */
 		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
 		return ret;
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
@@ -1195,7 +1195,9 @@ static int v4l_g_fmt(const struct v4l2_ioctl_ops *ops,
 	case V4L2_BUF_TYPE_VIDEO_OUTPUT:
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_g_fmt_vid_out))
 			break;
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
 		ret = ops->vidioc_g_fmt_vid_out(file, fh, arg);
+		/* just in case the driver zeroed it again */
 		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
 		return ret;
 	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
@@ -1231,6 +1233,7 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
 	bool is_sdr = vfd->vfl_type == VFL_TYPE_SDR;
 	bool is_rx = vfd->vfl_dir != VFL_DIR_TX;
 	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
+	int ret;
 
 	v4l_sanitize_format(p);
 
@@ -1239,7 +1242,10 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_s_fmt_vid_cap))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix);
-		return ops->vidioc_s_fmt_vid_cap(file, fh, arg);
+		ret = ops->vidioc_s_fmt_vid_cap(file, fh, arg);
+		/* just in case the driver zeroed it again */
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+		return ret;
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_s_fmt_vid_cap_mplane))
 			break;
@@ -1264,7 +1270,10 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_s_fmt_vid_out))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix);
-		return ops->vidioc_s_fmt_vid_out(file, fh, arg);
+		ret = ops->vidioc_s_fmt_vid_out(file, fh, arg);
+		/* just in case the driver zeroed it again */
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+		return ret;
 	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_s_fmt_vid_out_mplane))
 			break;
@@ -1303,6 +1312,7 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
 	bool is_sdr = vfd->vfl_type == VFL_TYPE_SDR;
 	bool is_rx = vfd->vfl_dir != VFL_DIR_TX;
 	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
+	int ret;
 
 	v4l_sanitize_format(p);
 
@@ -1311,7 +1321,10 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_try_fmt_vid_cap))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix);
-		return ops->vidioc_try_fmt_vid_cap(file, fh, arg);
+		ret = ops->vidioc_try_fmt_vid_cap(file, fh, arg);
+		/* just in case the driver zeroed it again */
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+		return ret;
 	case V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE:
 		if (unlikely(!is_rx || !is_vid || !ops->vidioc_try_fmt_vid_cap_mplane))
 			break;
@@ -1336,7 +1349,10 @@ static int v4l_try_fmt(const struct v4l2_ioctl_ops *ops,
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_try_fmt_vid_out))
 			break;
 		CLEAR_AFTER_FIELD(p, fmt.pix);
-		return ops->vidioc_try_fmt_vid_out(file, fh, arg);
+		ret = ops->vidioc_try_fmt_vid_out(file, fh, arg);
+		/* just in case the driver zeroed it again */
+		p->fmt.pix.priv = V4L2_PIX_FMT_PRIV_MAGIC;
+		return ret;
 	case V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE:
 		if (unlikely(!is_tx || !is_vid || !ops->vidioc_try_fmt_vid_out_mplane))
 			break;