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sch_cake: Make sure we can write the IP header before changing DSCP bits 

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>
hifive-unleashed-5.1
Toke Høiland-Jørgensen 2019-04-04 15:01:33 +02:00 committed by David S. Miller
parent b2100cc56f
commit c87b4ecdbe
1 changed files with 11 additions and 0 deletions
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11
net/sched/sch_cake.c
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@ -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);