Re: [PATCH] v4l2: fill the reserved fields of VIDIOC_REQBUFS ioctl

From: Trent Piepho
Date: Thu Apr 30 2009 - 12:20:21 EST

On Thu, 30 Apr 2009, Trent Piepho wrote:
> On Wed, 29 Apr 2009, [UTF-8] Németh Márton wrote:
> > The parameter of VIDIOC_REQBUFS is a pointer to struct v4l2_requestbuffers.
> > This structure has reserved fields which has to be filled with zeros
> > according to the V4L2 API specification, revision 0.24 [1].
>
> As I read the spec, the reserved fields can be used for input from user
> space if the buffer is of type V4L2_BUF_TYPE_PRIVATE or higher.

Here is a patch that fixes this problem, along with the S_FMT problem you
patched earlier. TRY_FMT had the same problem as S_FMT, so I fixed that
one as well too.

v4l2-ioctl: Clear buffer type specific trailing fields/padding

From: Trent Piepho <xyzzy@xxxxxxxxxxxxx>

Some ioctls have structs that are a different size depending on what type
of buffer is being used. If the buffer type leaves a field unused or has
padding space at the end, this space should be zeroed out.

The problems with S_FMT and REQBUFS were original identified and patched by
Márton Németh <nm127@xxxxxxxxxxx>.

Priority: normal

Signed-off-by: Trent Piepho <xyzzy@xxxxxxxxxxxxx>

diff -r 7b786cb576e5 -r 82ef5d6e29e3 linux/drivers/media/video/v4l2-ioctl.c
--- a/linux/drivers/media/video/v4l2-ioctl.c Thu Apr 30 09:14:13 2009 -0700
+++ b/linux/drivers/media/video/v4l2-ioctl.c Thu Apr 30 09:15:56 2009 -0700
@@ -42,6 +42,12 @@
if (vfd->debug & V4L2_DEBUG_IOCTL_ARG) \
printk(KERN_DEBUG "%s: " fmt, vfd->name, ## arg);\
} while (0)
+
+/* Zero out the end of the struct pointed to by p. Everthing after, but
+ * not including, the specified field is cleared. */
+#define CLEAR_AFTER_FIELD(p, field) \
+ memset((u8 *)(p) + offsetof(typeof(*(p)), field) + sizeof((p)->field), \
+ 0, sizeof(*(p)) - offsetof(typeof(*(p)), field) - sizeof((p)->field))

struct std_descr {
v4l2_std_id std;
@@ -783,44 +789,53 @@ static long __video_do_ioctl(struct file

switch (f->type) {
case V4L2_BUF_TYPE_VIDEO_CAPTURE:
+ CLEAR_AFTER_FIELD(f, fmt.pix);
v4l_print_pix_fmt(vfd, &f->fmt.pix);
if (ops->vidioc_s_fmt_vid_cap)
ret = ops->vidioc_s_fmt_vid_cap(file, fh, f);
break;
case V4L2_BUF_TYPE_VIDEO_OVERLAY:
+ CLEAR_AFTER_FIELD(f, fmt.win);
if (ops->vidioc_s_fmt_vid_overlay)
ret = ops->vidioc_s_fmt_vid_overlay(file,
fh, f);
break;
case V4L2_BUF_TYPE_VIDEO_OUTPUT:
+ CLEAR_AFTER_FIELD(f, fmt.pix);
v4l_print_pix_fmt(vfd, &f->fmt.pix);
if (ops->vidioc_s_fmt_vid_out)
ret = ops->vidioc_s_fmt_vid_out(file, fh, f);
break;
case V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY:
+ CLEAR_AFTER_FIELD(f, fmt.win);
if (ops->vidioc_s_fmt_vid_out_overlay)
ret = ops->vidioc_s_fmt_vid_out_overlay(file,
fh, f);
break;
case V4L2_BUF_TYPE_VBI_CAPTURE:
+ CLEAR_AFTER_FIELD(f, fmt.vbi);
if (ops->vidioc_s_fmt_vbi_cap)
ret = ops->vidioc_s_fmt_vbi_cap(file, fh, f);
break;
case V4L2_BUF_TYPE_VBI_OUTPUT:
+ CLEAR_AFTER_FIELD(f, fmt.vbi);
if (ops->vidioc_s_fmt_vbi_out)
ret = ops->vidioc_s_fmt_vbi_out(file, fh, f);
break;
case V4L2_BUF_TYPE_SLICED_VBI_CAPTURE:
+ CLEAR_AFTER_FIELD(f, fmt.sliced);
if (ops->vidioc_s_fmt_sliced_vbi_cap)
ret = ops->vidioc_s_fmt_sliced_vbi_cap(file,
fh, f);
break;
case V4L2_BUF_TYPE_SLICED_VBI_OUTPUT:
+ CLEAR_AFTER_FIELD(f, fmt.sliced);
if (ops->vidioc_s_fmt_sliced_vbi_out)
ret = ops->vidioc_s_fmt_sliced_vbi_out(file,
fh, f);
break;
case V4L2_BUF_TYPE_PRIVATE:
+ /* CLEAR_AFTER_FIELD(f, fmt.raw_data); <- does nothing */
if (ops->vidioc_s_fmt_type_private)
ret = ops->vidioc_s_fmt_type_private(file,
fh, f);
@@ -837,46 +852,55 @@ static long __video_do_ioctl(struct file
v4l2_type_names));
switch (f->type) {
case V4L2_BUF_TYPE_VIDEO_CAPTURE:
+ CLEAR_AFTER_FIELD(f, fmt.pix);
if (ops->vidioc_try_fmt_vid_cap)
ret = ops->vidioc_try_fmt_vid_cap(file, fh, f);
if (!ret)
v4l_print_pix_fmt(vfd, &f->fmt.pix);
break;
case V4L2_BUF_TYPE_VIDEO_OVERLAY:
+ CLEAR_AFTER_FIELD(f, fmt.win);
if (ops->vidioc_try_fmt_vid_overlay)
ret = ops->vidioc_try_fmt_vid_overlay(file,
fh, f);
break;
case V4L2_BUF_TYPE_VIDEO_OUTPUT:
+ CLEAR_AFTER_FIELD(f, fmt.pix);
if (ops->vidioc_try_fmt_vid_out)
ret = ops->vidioc_try_fmt_vid_out(file, fh, f);
if (!ret)
v4l_print_pix_fmt(vfd, &f->fmt.pix);
break;
case V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY:
+ CLEAR_AFTER_FIELD(f, fmt.win);
if (ops->vidioc_try_fmt_vid_out_overlay)
ret = ops->vidioc_try_fmt_vid_out_overlay(file,
fh, f);
break;
case V4L2_BUF_TYPE_VBI_CAPTURE:
+ CLEAR_AFTER_FIELD(f, fmt.vbi);
if (ops->vidioc_try_fmt_vbi_cap)
ret = ops->vidioc_try_fmt_vbi_cap(file, fh, f);
break;
case V4L2_BUF_TYPE_VBI_OUTPUT:
+ CLEAR_AFTER_FIELD(f, fmt.vbi);
if (ops->vidioc_try_fmt_vbi_out)
ret = ops->vidioc_try_fmt_vbi_out(file, fh, f);
break;
case V4L2_BUF_TYPE_SLICED_VBI_CAPTURE:
+ CLEAR_AFTER_FIELD(f, fmt.sliced);
if (ops->vidioc_try_fmt_sliced_vbi_cap)
ret = ops->vidioc_try_fmt_sliced_vbi_cap(file,
fh, f);
break;
case V4L2_BUF_TYPE_SLICED_VBI_OUTPUT:
+ CLEAR_AFTER_FIELD(f, fmt.sliced);
if (ops->vidioc_try_fmt_sliced_vbi_out)
ret = ops->vidioc_try_fmt_sliced_vbi_out(file,
fh, f);
break;
case V4L2_BUF_TYPE_PRIVATE:
+ /* CLEAR_AFTER_FIELD(f, fmt.raw_data); <- does nothing */
if (ops->vidioc_try_fmt_type_private)
ret = ops->vidioc_try_fmt_type_private(file,
fh, f);
@@ -898,6 +922,9 @@ static long __video_do_ioctl(struct file
ret = check_fmt(ops, p->type);
if (ret)
break;
+
+ if (p->type < V4L2_BUF_TYPE_PRIVATE)
+ CLEAR_AFTER_FIELD(p, memory);

ret = ops->vidioc_reqbufs(file, fh, p);
dbgarg(cmd, "count=%d, type=%s, memory=%s\n",
--
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