On Wed, Nov 24, 2021 at 05:20:45PM +0100, Arnaud Pouliquen wrote:
> Using OpenAMP library on remote side, when the rpmsg framework tries to
> reuse the buffer the following error message is displayed in
> the virtqueue_get_buf_ctx_split function:
> "virtio_rpmsg_bus virtio0: output:used len 28 is larger than in buflen 0"
>
> As described in virtio specification:
> "many drivers ignored the len value, as a result, many devices set len
> incorrectly. Thus, when using the legacy interface, it is generally
> a good idea to ignore the len value in used ring entries if possible."
>
> To stay in compliance with the legacy libraries, this patch prevents the
> virtio core from validating used length.
>
> Fixes: 939779f5152d ("virtio_ring: validate used buffer length")
>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
> Cc: Jason Wang <jasowang@xxxxxxxxxx>
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
Arnaud, thanks a lot for the analysis.
Jason, I think this is another good point. We really should not
validate input for legacy devices at all.
> Update vs v1[1]: update commit message to clarify the context.
>
> base-commit: fa55b7dcdc43c1aa1ba12bca9d2dd4318c2a0dbf
>
> [1]https://lore.kernel.org/lkml/20211122160812.25125-1-arnaud.pouliquen@xxxxxxxxxxx/T/
> ---
> drivers/rpmsg/virtio_rpmsg_bus.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
> index 9c112aa65040..5f73f19c2c38 100644
> --- a/drivers/rpmsg/virtio_rpmsg_bus.c
> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c
> @@ -1054,6 +1054,7 @@ static struct virtio_driver virtio_ipc_driver = {
> .feature_table_size = ARRAY_SIZE(features),
> .driver.name = KBUILD_MODNAME,
> .driver.owner = THIS_MODULE,
> + .suppress_used_validation = true,
> .id_table = id_table,
> .probe = rpmsg_probe,
> .remove = rpmsg_remove,
> --
> 2.17.1
