[PATCH bpf 2/2] xsk: fix to reject invalid options in Tx descriptor

[Björn Töpel]

From: Björn Töpel <bjorn.to...@intel.com>

Passing a non-existing option in the options member of struct
xdp_desc, 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.to...@intel.com>
---
 net/xdp/xsk_queue.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk_queue.h b/net/xdp/xsk_queue.h
index bcb5cbb40419..610c0bdc0c2b 100644
--- 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;
        }
-- 
2.19.1