sch_cake: Make sure we can write the IP header before changing DSCP bits (c87b4ecd) · Commits · 戴 / test

There is not actually any guarantee that the IP headers are valid before we access the DSCP bits of the packets. Fix this using the same approach taken in sch_dsmark. Reported-by:

Kevin Darbyshire-Bryant <kevin@darbyshire-bryant.me.uk> Signed-off-by:

Toke Høiland-Jørgensen <toke@redhat.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/sched/sch_cake.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -1517,16 +1517,27 @@ static unsigned int cake_drop(struct Qdisc sch, struct sk_buff *to_free)

		static u8 cake_handle_diffserv(struct sk_buff *skb, u16 wash)
		{
		int wlen = skb_network_offset(skb);
		u8 dscp;

		switch (tc_skb_protocol(skb)) {
		case htons(ETH_P_IP):
		wlen += sizeof(struct iphdr);
		if (!pskb_may_pull(skb, wlen) \|\|
		skb_try_make_writable(skb, wlen))
		return 0;

		dscp = ipv4_get_dsfield(ip_hdr(skb)) >> 2;
		if (wash && dscp)
		ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, 0);
		return dscp;

		case htons(ETH_P_IPV6):
		wlen += sizeof(struct ipv6hdr);
		if (!pskb_may_pull(skb, wlen) \|\|
		skb_try_make_writable(skb, wlen))
		return 0;

		dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> 2;
		if (wash && dscp)
		ipv6_change_dsfield(ipv6_hdr(skb), INET_ECN_MASK, 0);

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