On Fri, 8 Mar 2019 08:57:26 +0100
Björn Töpel <bjorn.topel@xxxxxxxxx> wrote:
> From: Björn Töpel <bjorn.topel@xxxxxxxxx>
>
> Passing a non-existing flag in the sxdp_flags member of struct
> sockaddr_xdp was, incorrectly, silently ignored. This patch addresses
> that behavior, and rejects any non-existing flags.
>
> We have examined existing user space code, and to our best knowledge,
> no one is relying on the current incorrect behavior. AF_XDP is still
> in its infancy, so from our perspective, the risk of breakage is very
> low, and addressing this problem now is important.
>
> Fixes: 965a99098443 ("xsk: add support for bind for Rx")
> Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx>
> ---
> net/xdp/xsk.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 6697084e3fdf..a14e8864e4fa 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -407,6 +407,10 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
> if (sxdp->sxdp_family != AF_XDP)
> return -EINVAL;
>
> + flags = sxdp->sxdp_flags;
> + if (flags & ~(XDP_SHARED_UMEM | XDP_COPY | XDP_ZEROCOPY))
> + return -EINVAL;
> +
What about setting more than one flag at a time? Is it allowed/make any sense?
After a quick look it seems that they exclude each other, e.g. you can't force
a zero copy and copy mode at the same time. And for XDP_SHARED_UMEM two
remaining flags can't be set.
So maybe check here also that only one particular flag is set by doing:
if (hweight32(flags & (XDP_SHARED_UMEM | XDP_COPY | XDP_ZEROCOPY)) > 1)
return -EINVAL;
just like we do it for IFLA_XDP_FLAGS in net/core/rtnetlink.c?
> mutex_lock(&xs->mutex);
> if (xs->dev) {
> err = -EBUSY;
> @@ -425,7 +429,6 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
> }
>
> qid = sxdp->sxdp_queue_id;
> - flags = sxdp->sxdp_flags;
>
> if (flags & XDP_SHARED_UMEM) {
> struct xdp_sock *umem_xs;
