From: Nikhil P. Rao <nikhil.rao@amd.com>
Date: Wed, 25 Feb 2026 00:00:27 +0000 (+0000)
Subject: xsk: Fix zero-copy AF_XDP fragment drop
X-Git-Tag: v7.0-rc3~39^2~45^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f7387d6579d65efd490a864254101cb665f2e7a7;p=thirdparty%2Fkernel%2Fstable.git

xsk: Fix zero-copy AF_XDP fragment drop

AF_XDP should ensure that only a complete packet is sent to application.
In the zero-copy case, if the Rx queue gets full as fragments are being
enqueued, the remaining fragments are dropped.

For the multi-buffer case, add a check to ensure that the Rx queue has
enough space for all fragments of a packet before starting to enqueue
them.

Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX")
Signed-off-by: Nikhil P. Rao <nikhil.rao@amd.com>
Link: https://patch.msgid.link/20260225000456.107806-3-nikhil.rao@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index be882a8d473c3..6149f6a798971 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -167,25 +167,31 @@ static int xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 	struct xdp_buff_xsk *pos, *tmp;
 	struct list_head *xskb_list;
 	u32 contd = 0;
+	u32 num_desc;
 	int err;
 
-	if (frags)
-		contd = XDP_PKT_CONTD;
+	if (likely(!frags)) {
+		err = __xsk_rcv_zc(xs, xskb, len, contd);
+		if (err)
+			goto err;
+		return 0;
+	}
 
-	err = __xsk_rcv_zc(xs, xskb, len, contd);
-	if (err)
+	contd = XDP_PKT_CONTD;
+	num_desc = xdp_get_shared_info_from_buff(xdp)->nr_frags + 1;
+	if (xskq_prod_nb_free(xs->rx, num_desc) < num_desc) {
+		xs->rx_queue_full++;
+		err = -ENOBUFS;
 		goto err;
-	if (likely(!frags))
-		return 0;
+	}
 
+	__xsk_rcv_zc(xs, xskb, len, contd);
 	xskb_list = &xskb->pool->xskb_list;
 	list_for_each_entry_safe(pos, tmp, xskb_list, list_node) {
 		if (list_is_singular(xskb_list))
 			contd = 0;
 		len = pos->xdp.data_end - pos->xdp.data;
-		err = __xsk_rcv_zc(xs, pos, len, contd);
-		if (err)
-			goto err;
+		__xsk_rcv_zc(xs, pos, len, contd);
 		list_del_init(&pos->list_node);
 	}