[PATCH 1/2] ASoC: SOF: sof-client-probes: fix error codes in sof_probes_compr_copy()

[Dan Carpenter]

On Wed, Jul 06, 2022 at 01:21:59PM +0300, Dan Carpenter wrote:
> On Wed, Jul 06, 2022 at 12:05:37PM +0300, Péter Ujfalusi wrote:
> > 
> > 
> > On 06/07/2022 10:23, Dan Carpenter wrote:
> > > This function tries to return the number of bytes that it was able to
> > > copy to the user.  However, because there are multiple calls to
> > > copy_to_user() in a row that means the bytes are not necessarily
> > > consecutive so it's not useful.  Just return -EFAULT instead.
> > 
> > The function is copying data from a circular buffer to a use buffer.
> > The single copy_to_user() is used when we don't have wrapping, the
> > 'double' copy_to_user() is when we wrap, so first copy is from the end
> > of the buffer then we copy the data from the start of the buffer to get
> > all data.
> 
> Ok.  But the bugs in the original code are real.  I will resend.

Actually that's not true.  The bugs in the original code are something
that only affect users who deserve it?  I might not resend.  A fix would
look something like below?

regards,
dan carpenter

diff --git a/sound/soc/sof/sof-client-probes.c b/sound/soc/sof/sof-client-probes.c
index 1f1ea93a7fbf..32fa3186c295 100644
--- a/sound/soc/sof/sof-client-probes.c
+++ b/sound/soc/sof/sof-client-probes.c
@@ -398,9 +398,14 @@ static int sof_probes_compr_copy(struct snd_soc_component *component,
 		ret = copy_to_user(buf, ptr, count);
 	} else {
 		ret = copy_to_user(buf, ptr, n);
-		ret += copy_to_user(buf + n, rtd->dma_area, count - n);
+		if (ret) {
+			ret += count - n;
+			goto done;
+		}
+		ret = copy_to_user(buf + n, rtd->dma_area, count - n);
 	}
 
+done:
 	if (ret)
 		return count - ret;
 	return count;