Re: user accesses in ivtv-fileops.c:ivtv_v4l2_write ?

Re: user accesses in ivtv-fileops.c:ivtv_v4l2_write ?

[Andy Walls]

On Sun, 2010-11-28 at 17:40 +0000, Dr. David Alan Gilbert wrote:
> Hi,
>   Sparse pointed me at the following line in ivtv-fileops.c's ivtv_v4l2_write:
> 
>                 ivtv_write_vbi(itv, (const struct v4l2_sliced_vbi_data *)user_buf, elems);
> 

Hi David,

Let me know if this patch works for your sparse build and adequately
addresses the problem.

It might be easiest to review this patch by starting at the bottom and
working your way up.

Regards,
Andy


ivtv: ivtv_write_vbi() should use copy_from_user() for user data buffers

ivtv_write_vbi() is used to output VBI data to a TV screen using the
CX23415's decoder.  It was used for both VBI data that came from the
driver internally and VBI data that came from the user, but did not use
copy_from_user() for reading the VBI data from the user buffers.

This change adds a new version of the function,
ivtv_write_vbi_from_user(), that uses copy_from_user() to read the VBI
data provided via user buffers.

This should resolve an sparse build warning reported by Dave Gilbert.

Reported-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Andy Walls <awalls@md.metrocast.net>


diff --git a/drivers/media/video/ivtv/ivtv-fileops.c b/drivers/media/video/ivtv/ivtv-fileops.c
index d727485..4f46b00 100644
--- a/drivers/media/video/ivtv/ivtv-fileops.c
+++ b/drivers/media/video/ivtv/ivtv-fileops.c
@@ -570,7 +570,8 @@ ssize_t ivtv_v4l2_write(struct file *filp, const char __user *user_buf, size_t c
 		int elems = count / sizeof(struct v4l2_sliced_vbi_data);
 
 		set_bit(IVTV_F_S_APPL_IO, &s->s_flags);
-		ivtv_write_vbi(itv, (const struct v4l2_sliced_vbi_data *)user_buf, elems);
+		ivtv_write_vbi_from_user(itv,
+		   (const struct v4l2_sliced_vbi_data __user *)user_buf, elems);
 		return elems * sizeof(struct v4l2_sliced_vbi_data);
 	}
 
diff --git a/drivers/media/video/ivtv/ivtv-vbi.c b/drivers/media/video/ivtv/ivtv-vbi.c
index e1c347e..7275f2d 100644
--- a/drivers/media/video/ivtv/ivtv-vbi.c
+++ b/drivers/media/video/ivtv/ivtv-vbi.c
@@ -92,54 +92,91 @@ static int odd_parity(u8 c)
 	return c & 1;
 }
 
-void ivtv_write_vbi(struct ivtv *itv, const struct v4l2_sliced_vbi_data *sliced, size_t cnt)
+static void ivtv_write_vbi_line(struct ivtv *itv,
+				const struct v4l2_sliced_vbi_data *d,
+				struct vbi_cc *cc, int *found_cc)
 {
 	struct vbi_info *vi = &itv->vbi;
-	struct vbi_cc cc = { .odd = { 0x80, 0x80 }, .even = { 0x80, 0x80 } };
-	int found_cc = 0;
-	size_t i;
-
-	for (i = 0; i < cnt; i++) {
-		const struct v4l2_sliced_vbi_data *d = sliced + i;
 
-		if (d->id == V4L2_SLICED_CAPTION_525 && d->line == 21) {
-			if (d->field) {
-				cc.even[0] = d->data[0];
-				cc.even[1] = d->data[1];
-			} else {
-				cc.odd[0] = d->data[0];
-				cc.odd[1] = d->data[1];
-			}
-			found_cc = 1;
+	if (d->id == V4L2_SLICED_CAPTION_525 && d->line == 21) {
+		if (d->field) {
+			cc->even[0] = d->data[0];
+			cc->even[1] = d->data[1];
+		} else {
+			cc->odd[0] = d->data[0];
+			cc->odd[1] = d->data[1];
 		}
-		else if (d->id == V4L2_SLICED_VPS && d->line == 16 && d->field == 0) {
-			struct vbi_vps vps;
-
-			vps.data[0] = d->data[2];
-			vps.data[1] = d->data[8];
-			vps.data[2] = d->data[9];
-			vps.data[3] = d->data[10];
-			vps.data[4] = d->data[11];
-			if (memcmp(&vps, &vi->vps_payload, sizeof(vps))) {
-				vi->vps_payload = vps;
-				set_bit(IVTV_F_I_UPDATE_VPS, &itv->i_flags);
-			}
+		*found_cc = 1;
+	} else if (d->id == V4L2_SLICED_VPS && d->line == 16 && d->field == 0) {
+		struct vbi_vps vps;
+
+		vps.data[0] = d->data[2];
+		vps.data[1] = d->data[8];
+		vps.data[2] = d->data[9];
+		vps.data[3] = d->data[10];
+		vps.data[4] = d->data[11];
+		if (memcmp(&vps, &vi->vps_payload, sizeof(vps))) {
+			vi->vps_payload = vps;
+			set_bit(IVTV_F_I_UPDATE_VPS, &itv->i_flags);
 		}
-		else if (d->id == V4L2_SLICED_WSS_625 && d->line == 23 && d->field == 0) {
-			int wss = d->data[0] | d->data[1] << 8;
+	} else if (d->id == V4L2_SLICED_WSS_625 &&
+		   d->line == 23 && d->field == 0) {
+		int wss = d->data[0] | d->data[1] << 8;
 
-			if (vi->wss_payload != wss) {
-				vi->wss_payload = wss;
-				set_bit(IVTV_F_I_UPDATE_WSS, &itv->i_flags);
-			}
+		if (vi->wss_payload != wss) {
+			vi->wss_payload = wss;
+			set_bit(IVTV_F_I_UPDATE_WSS, &itv->i_flags);
 		}
 	}
-	if (found_cc && vi->cc_payload_idx < ARRAY_SIZE(vi->cc_payload)) {
-		vi->cc_payload[vi->cc_payload_idx++] = cc;
+}
+
+static void ivtv_write_vbi_cc_lines(struct ivtv *itv, const struct vbi_cc *cc)
+{
+	struct vbi_info *vi = &itv->vbi;
+
+	if (vi->cc_payload_idx < ARRAY_SIZE(vi->cc_payload)) {
+		memcpy(&vi->cc_payload[vi->cc_payload_idx], cc,
+		       sizeof(struct vbi_cc));
+		vi->cc_payload_idx++;
 		set_bit(IVTV_F_I_UPDATE_CC, &itv->i_flags);
 	}
 }
 
+static void ivtv_write_vbi(struct ivtv *itv,
+			   const struct v4l2_sliced_vbi_data *sliced,
+			   size_t cnt)
+{
+	struct vbi_cc cc = { .odd = { 0x80, 0x80 }, .even = { 0x80, 0x80 } };
+	int found_cc = 0;
+	size_t i;
+
+	for (i = 0; i < cnt; i++)
+		ivtv_write_vbi_line(itv, sliced + i, &cc, &found_cc);
+
+	if (found_cc)
+		ivtv_write_vbi_cc_lines(itv, &cc);
+}
+
+void ivtv_write_vbi_from_user(struct ivtv *itv,
+			      const struct v4l2_sliced_vbi_data __user *sliced,
+			      size_t cnt)
+{
+	struct vbi_cc cc = { .odd = { 0x80, 0x80 }, .even = { 0x80, 0x80 } };
+	int found_cc = 0;
+	size_t i;
+	struct v4l2_sliced_vbi_data d;
+
+	for (i = 0; i < cnt; i++) {
+		if (copy_from_user(&d, sliced + i,
+				   sizeof(struct v4l2_sliced_vbi_data)))
+			break;
+		ivtv_write_vbi_line(itv, sliced + i, &cc, &found_cc);
+	}
+
+	if (found_cc)
+		ivtv_write_vbi_cc_lines(itv, &cc);
+}
+
 static void copy_vbi_data(struct ivtv *itv, int lines, u32 pts_stamp)
 {
 	int line = 0;
diff --git a/drivers/media/video/ivtv/ivtv-vbi.h b/drivers/media/video/ivtv/ivtv-vbi.h
index 970567b..eda38d0 100644
--- a/drivers/media/video/ivtv/ivtv-vbi.h
+++ b/drivers/media/video/ivtv/ivtv-vbi.h
@@ -20,7 +20,9 @@
 #ifndef IVTV_VBI_H
 #define IVTV_VBI_H
 
-void ivtv_write_vbi(struct ivtv *itv, const struct v4l2_sliced_vbi_data *sliced, size_t count);
+void ivtv_write_vbi_from_user(struct ivtv *itv,
+			      const struct v4l2_sliced_vbi_data __user *sliced,
+			      size_t count);
 void ivtv_process_vbi_data(struct ivtv *itv, struct ivtv_buffer *buf,
 			   u64 pts_stamp, int streamtype);
 int ivtv_used_line(struct ivtv *itv, int line, int field);

Re: user accesses in ivtv-fileops.c:ivtv_v4l2_write ?

[Dr. David Alan Gilbert]

* Andy Walls (awalls@md.metrocast.net) wrote:
> On Sun, 2010-11-28 at 17:40 +0000, Dr. David Alan Gilbert wrote:
> > Hi,
> >   Sparse pointed me at the following line in ivtv-fileops.c's ivtv_v4l2_write:
> > 
> >                 ivtv_write_vbi(itv, (const struct v4l2_sliced_vbi_data *)user_buf, elems);
> > 
> 
> Hi David,
> 
> Let me know if this patch works for your sparse build and adequately
> addresses the problem.

Hi Andy,
  Yes that seems to fix it.
The only other comment I have is that it would probably be better if
ivtv_write_vbi_from_user() were to return an error if the copy_from_user
were to fail and then pass that all the way back up so that if an app passed
a bad pointer in it would get an EFAULT or the like.

Thanks,

Dave
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\ gro.gilbert @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: user accesses in ivtv-fileops.c:ivtv_v4l2_write ?

[Dr. David Alan Gilbert]

Hi Andy,
  It looks like we missed something in that copy from user
patch from the end of last year:

+void ivtv_write_vbi_from_user(struct ivtv *itv,
+                             const struct v4l2_sliced_vbi_data __user *sliced,
+                             size_t cnt)
+{
+       struct vbi_cc cc = { .odd = { 0x80, 0x80 }, .even = { 0x80, 0x80 } };
+       int found_cc = 0;
+       size_t i;
+       struct v4l2_sliced_vbi_data d;
+
+       for (i = 0; i < cnt; i++) {
+               if (copy_from_user(&d, sliced + i,
+                                  sizeof(struct v4l2_sliced_vbi_data)))
+                       break;
+               ivtv_write_vbi_line(itv, sliced + i, &cc, &found_cc);


sparse is giving me:
drivers/media/video/ivtv/ivtv-vbi.c:177:49: warning: incorrect type in argument 2 (different address spaces)
drivers/media/video/ivtv/ivtv-vbi.c:177:49:    expected struct v4l2_sliced_vbi_data const *d
drivers/media/video/ivtv/ivtv-vbi.c:177:49:    got struct v4l2_sliced_vbi_data const [noderef] <asn:1>*

and I think the point is that while you've copied the data I think
you're still passing the user pointer to ivtv_write_vbi_line and it 
should be:

               ivtv_write_vbi_line(itv, &d, &cc, &found_cc);


What do you think?

Dave


-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\ gro.gilbert @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/

Re: user accesses in ivtv-fileops.c:ivtv_v4l2_write ?

[Andy Walls]

On Sun, 2011-01-09 at 00:34 +0000, Dr. David Alan Gilbert wrote:
> Hi Andy,
>   It looks like we missed something in that copy from user
> patch from the end of last year:
> 
> +void ivtv_write_vbi_from_user(struct ivtv *itv,
> +                             const struct v4l2_sliced_vbi_data __user *sliced,
> +                             size_t cnt)
> +{
> +       struct vbi_cc cc = { .odd = { 0x80, 0x80 }, .even = { 0x80, 0x80 } };
> +       int found_cc = 0;
> +       size_t i;
> +       struct v4l2_sliced_vbi_data d;
> +
> +       for (i = 0; i < cnt; i++) {
> +               if (copy_from_user(&d, sliced + i,
> +                                  sizeof(struct v4l2_sliced_vbi_data)))
> +                       break;
> +               ivtv_write_vbi_line(itv, sliced + i, &cc, &found_cc);
                                           ^^^^^^^^^^
What was I thinking?  ---------------------+

Decent plan; failed execution. :(


> 
> sparse is giving me:
> drivers/media/video/ivtv/ivtv-vbi.c:177:49: warning: incorrect type in argument 2 (different address spaces)
> drivers/media/video/ivtv/ivtv-vbi.c:177:49:    expected struct v4l2_sliced_vbi_data const *d
> drivers/media/video/ivtv/ivtv-vbi.c:177:49:    got struct v4l2_sliced_vbi_data const [noderef] <asn:1>*
> 
> and I think the point is that while you've copied the data I think
> you're still passing the user pointer to ivtv_write_vbi_line and it 
> should be:
> 
>                ivtv_write_vbi_line(itv, &d, &cc, &found_cc);
> 
> 
> What do you think?

Yes, it looks like I gooned that one up. :)

That's what I get for trying to fix things with the kids running around
before bedtime.

I assume that you have made the replacement and tested that sparse is
satisfied?

Regards,
Andy

Re: user accesses in ivtv-fileops.c:ivtv_v4l2_write ?

[Dr. David Alan Gilbert]

* Andy Walls (awalls@md.metrocast.net) wrote:
> On Sun, 2011-01-09 at 00:34 +0000, Dr. David Alan Gilbert wrote:
> > Hi Andy,
> >   It looks like we missed something in that copy from user
> > patch from the end of last year:
> > 
> > +void ivtv_write_vbi_from_user(struct ivtv *itv,
> > +                             const struct v4l2_sliced_vbi_data __user *sliced,
> > +                             size_t cnt)
> > +{
> > +       struct vbi_cc cc = { .odd = { 0x80, 0x80 }, .even = { 0x80, 0x80 } };
> > +       int found_cc = 0;
> > +       size_t i;
> > +       struct v4l2_sliced_vbi_data d;
> > +
> > +       for (i = 0; i < cnt; i++) {
> > +               if (copy_from_user(&d, sliced + i,
> > +                                  sizeof(struct v4l2_sliced_vbi_data)))
> > +                       break;
> > +               ivtv_write_vbi_line(itv, sliced + i, &cc, &found_cc);
>                                            ^^^^^^^^^^
> What was I thinking?  ---------------------+
> 
> Decent plan; failed execution. :(

Sorry for not spotting it when you sent it out last time!

> > sparse is giving me:
> > drivers/media/video/ivtv/ivtv-vbi.c:177:49: warning: incorrect type in argument 2 (different address spaces)
> > drivers/media/video/ivtv/ivtv-vbi.c:177:49:    expected struct v4l2_sliced_vbi_data const *d
> > drivers/media/video/ivtv/ivtv-vbi.c:177:49:    got struct v4l2_sliced_vbi_data const [noderef] <asn:1>*
> > 
> > and I think the point is that while you've copied the data I think
> > you're still passing the user pointer to ivtv_write_vbi_line and it 
> > should be:
> > 
> >                ivtv_write_vbi_line(itv, &d, &cc, &found_cc);
> > 
> > 
> > What do you think?
> 
> Yes, it looks like I gooned that one up. :)
> 
> That's what I get for trying to fix things with the kids running around
> before bedtime.
> 
> I assume that you have made the replacement and tested that sparse is
> satisfied?

Yes, seems happy - of course I thought I did last time :-)

Dave
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
/ Dr. David Alan Gilbert    |       Running GNU/Linux       | Happy  \ 
\ gro.gilbert @ treblig.org |                               | In Hex /
 \ _________________________|_____ http://www.treblig.org   |_______/