xsk: fix to reject invalid options in Tx descriptor

Passing a non-existing option in the options member of struct
xdp_desc was, incorrectly, silently ignored. This patch addresses
that behavior, and drops any Tx descriptor with non-existing options.

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: 35fcde7f8deb ("xsk: support for Tx")
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index bcb5cbb..610c0bd 100644 (file)
--- a/net/xdp/xsk_queue.h
+++ b/net/xdp/xsk_queue.h
@@ -174,8 +174,8 @@ static inline bool xskq_is_valid_desc(struct xsk_queue *q, struct xdp_desc *d)
        if (!xskq_is_valid_addr(q, d->addr))
                return false;
 
-       if (((d->addr + d->len) & q->chunk_mask) !=
-           (d->addr & q->chunk_mask)) {
+       if (((d->addr + d->len) & q->chunk_mask) != (d->addr & q->chunk_mask) ||
+           d->options) {
                q->invalid_descs++;
                return false;
        }