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Commit 312de5a0 authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Greg Kroah-Hartman
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net: fix generic XDP to handle if eth header was mangled 



[ Upstream commit 2972495699320229b55b8e5065a310be5c81485b ]

XDP can modify (and resize) the Ethernet header in the packet.

There is a bug in generic-XDP, because skb->protocol and skb->pkt_type
are setup before reaching (netif_receive_)generic_xdp.

This bug was hit when XDP were popping VLAN headers (changing
eth->h_proto), as skb->protocol still contains VLAN-indication
(ETH_P_8021Q) causing invocation of skb_vlan_untag(skb), which corrupt
the packet (basically popping the VLAN again).

This patch catch if XDP changed eth header in such a way, that SKB
fields needs to be updated.

V2: on request from Song Liu, use ETH_HLEN instead of mac_len,
in __skb_push() as eth_type_trans() use ETH_HLEN in paired skb_pull_inline().

Fixes: d4455169 ("net: xdp: support xdp generic on virtual devices")
Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 01404588

net/core/dev.c

+14 −0
Original line number Diff line number Diff line
@@ -4296,6 +4296,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb, 
	struct netdev_rx_queue *rxqueue;

	void *orig_data, *orig_data_end;

	u32 metalen, act = XDP_DROP;

	__be16 orig_eth_type;

	struct ethhdr *eth;

	bool orig_bcast;

	int hlen, off;

	u32 mac_len;
@@ -4336,6 +4339,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb, 
	xdp->data_hard_start = skb->data - skb_headroom(skb);

	orig_data_end = xdp->data_end;

	orig_data = xdp->data;

	eth = (struct ethhdr *)xdp->data;

	orig_bcast = is_multicast_ether_addr_64bits(eth->h_dest);

	orig_eth_type = eth->h_proto;



	rxqueue = netif_get_rxqueue(skb);

	xdp->rxq = &rxqueue->xdp_rxq;
@@ -4359,6 +4365,14 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb, 


	}



	/* check if XDP changed eth hdr such SKB needs update */

	eth = (struct ethhdr *)xdp->data;

	if ((orig_eth_type != eth->h_proto) ||

	    (orig_bcast != is_multicast_ether_addr_64bits(eth->h_dest))) {

		__skb_push(skb, ETH_HLEN);

		skb->protocol = eth_type_trans(skb, skb->dev);

	}



	switch (act) {

	case XDP_REDIRECT:

	case XDP_TX: