netdev - [PATCH v8 bpf-next 04/10] xdp: Helper function to clear kernel pointers in xdp

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Date:   Fri,  3 Aug 2018 16:58:12 +0900
From:   Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
        netdev@...r.kernel.org, Jesper Dangaard Brouer <brouer@...hat.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        John Fastabend <john.fastabend@...il.com>
Subject: [PATCH v8 bpf-next 04/10] xdp: Helper function to clear kernel pointers in xdp_frame

xdp_frame has kernel pointers which should not be readable from bpf
programs. When we want to reuse xdp_frame region but it may be read by
bpf programs later, we can use this helper to clear kernel pointers.
This is more efficient than calling memset() for the entire struct.

Signed-off-by: Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
---
 include/net/xdp.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index fcb033f..76b9525 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -84,6 +84,13 @@ struct xdp_frame {
 	struct net_device *dev_rx; /* used by cpumap */
 };
 
+/* Clear kernel pointers in xdp_frame */
+static inline void xdp_scrub_frame(struct xdp_frame *frame)
+{
+	frame->data = NULL;
+	frame->dev_rx = NULL;
+}
+
 /* Convert xdp_buff to xdp_frame */
 static inline
 struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
-- 
1.8.3.1