2 files changed, 40 insertions, 11 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index a490ef643586..3e8ac127a7e1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3997,9 +3997,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 				     struct bpf_prog *xdp_prog)
 {
 	struct netdev_rx_queue *rxqueue;
+	void *orig_data, *orig_data_end;
 	u32 metalen, act = XDP_DROP;
 	struct xdp_buff xdp;
-	void *orig_data;
 	int hlen, off;
 	u32 mac_len;
 
@@ -4038,6 +4038,7 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 	xdp.data_meta = xdp.data;
 	xdp.data_end = xdp.data + hlen;
 	xdp.data_hard_start = skb->data - skb_headroom(skb);
+	orig_data_end = xdp.data_end;
 	orig_data = xdp.data;
 
 	rxqueue = netif_get_rxqueue(skb);
@@ -4052,6 +4053,13 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 		__skb_push(skb, -off);
 	skb->mac_header += off;
 
+	/* check if bpf_xdp_adjust_tail was used. it can only "shrink"
+	 * pckt.
+	 */
+	off = orig_data_end - xdp.data_end;
+	if (off != 0)
+		skb_set_tail_pointer(skb, xdp.data_end - xdp.data);
+
 	switch (act) {
 	case XDP_REDIRECT:
 	case XDP_TX:
diff --git a/net/core/filter.c b/net/core/filter.c
index a374b8560bc4..e25bc4a3aa1a 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2694,20 +2694,13 @@ BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset)
 {
 	void *xdp_frame_end = xdp->data_hard_start + sizeof(struct xdp_frame);
 	unsigned long metalen = xdp_get_metalen(xdp);
-	void *data_start = xdp->data_hard_start + metalen;
+	void *data_start = xdp_frame_end + metalen;
 	void *data = xdp->data + offset;
 
 	if (unlikely(data < data_start ||
 		     data > xdp->data_end - ETH_HLEN))
 		return -EINVAL;
 
-	/* Avoid info leak, when reusing area prev used by xdp_frame */
-	if (data < xdp_frame_end) {
-		unsigned long clearlen = xdp_frame_end - data;
-
-		memset(data, 0, clearlen);
-	}
-
 	if (metalen)
 		memmove(xdp->data_meta + offset,
 			xdp->data_meta, metalen);
@@ -2725,14 +2718,39 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
+BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset)
+{
+	void *data_end = xdp->data_end + offset;
+
+	/* only shrinking is allowed for now. */
+	if (unlikely(offset >= 0))
+		return -EINVAL;
+
+	if (unlikely(data_end < xdp->data + ETH_HLEN))
+		return -EINVAL;
+
+	xdp->data_end = data_end;
+
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_xdp_adjust_tail_proto = {
+	.func		= bpf_xdp_adjust_tail,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+};
+
 BPF_CALL_2(bpf_xdp_adjust_meta, struct xdp_buff *, xdp, int, offset)
 {
+	void *xdp_frame_end = xdp->data_hard_start + sizeof(struct xdp_frame);
 	void *meta = xdp->data_meta + offset;
 	unsigned long metalen = xdp->data - meta;
 
 	if (xdp_data_meta_unsupported(xdp))
 		return -ENOTSUPP;
-	if (unlikely(meta < xdp->data_hard_start ||
+	if (unlikely(meta < xdp_frame_end ||
 		     meta > xdp->data))
 		return -EINVAL;
 	if (unlikely((metalen & (sizeof(__u32) - 1)) ||
@@ -3074,7 +3092,8 @@ bool bpf_helper_changes_pkt_data(void *func)
 	    func == bpf_l4_csum_replace ||
 	    func == bpf_xdp_adjust_head ||
 	    func == bpf_xdp_adjust_meta ||
-	    func == bpf_msg_pull_data)
+	    func == bpf_msg_pull_data ||
+	    func == bpf_xdp_adjust_tail)
 		return true;
 
 	return false;
@@ -3888,6 +3907,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_xdp_redirect_proto;
 	case BPF_FUNC_redirect_map:
 		return &bpf_xdp_redirect_map_proto;
+	case BPF_FUNC_xdp_adjust_tail:
+		return &bpf_xdp_adjust_tail_proto;
 	default:
 		return bpf_base_func_proto(func_id);
 	}