The return value of copy_to_iter can't be negative, check whether the
copied length is equal to the requested length instead of checking for
negative values.

Cc: zhang jiao <zhangjiao2@cmss.chinamobile.com>
Link: https://lore.kernel.org/all/20250910091739.2999-1-zhangjiao2@cmss.chinamobile.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---


Lightly tested. zhang jiao could you pls also test, either ack or
fold into your patch?

 drivers/vhost/vringh.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 0c8a17cbb22e..925858cc6096 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1162,6 +1162,7 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 		struct iov_iter iter;
 		u64 translated;
 		int ret;
+		size_t size;
 
 		ret = iotlb_translate(vrh, (u64)(uintptr_t)dst,
 				      len - total_translated, &translated,
@@ -1179,9 +1180,9 @@ static inline int copy_to_iotlb(const struct vringh *vrh, void *dst,
 				      translated);
 		}
 
-		ret = copy_to_iter(src, translated, &iter);
-		if (ret < 0)
-			return ret;
+		size = copy_to_iter(src, translated, &iter);
+		if (size != translated)
+			return -EFAULT;
 
 		src += translated;
 		dst += translated;
-- 
MST

On Wed, Sep 24, 2025 at 5:48 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> The return value of copy_to_iter can't be negative, check whether the
> copied length is equal to the requested length instead of checking for
> negative values.
>
> Cc: zhang jiao <zhangjiao2@cmss.chinamobile.com>
> Link: https://lore.kernel.org/all/20250910091739.2999-1-zhangjiao2@cmss.chinamobile.com
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

Tested this patch with virtio-net regression tests, everything works fine.

Tested-by: Lei Yang <leiyang@redhat.com>

On Wed, Sep 24, 2025 at 8:54 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Wed, Sep 24, 2025 at 5:48 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > The return value of copy_to_iter can't be negative, check whether the
> > copied length is equal to the requested length instead of checking for
> > negative values.
> >
> > Cc: zhang jiao <zhangjiao2@cmss.chinamobile.com>
> > Link: https://lore.kernel.org/all/20250910091739.2999-1-zhangjiao2@cmss.chinamobile.com
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> >
>
> Acked-by: Jason Wang <jasowang@redhat.com>
>
> Thanks
>
>