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

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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>
This commit is contained in:
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);