[PATCH AUTOSEL 5.0 016/262] xsk: fix to reject invalid flags in xsk_bind

[Sasha Levin]

From: BjÃrn TÃpel <bjorn.topel@xxxxxxxxx>

[ Upstream commit f54ba391d88f5a5d032175b4c308c176e34b80b7 ]

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: BjÃrn TÃpel <bjorn.topel@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 85e4fe4f18cc..f3031c8907d9 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;
+
 	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;
-- 
2.19.1