Similar to commit bc6bcb59 ("netfilter: xt_TCPOPTSTRIP: fix possible mangling
beyond packet boundary"), add safe fragment handling to xt_TCPMSS.
Phil
Signed-off-by: Phil Oester <kernel@xxxxxxxxxxxx>
diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c
index a75240f..d81b760 100644
--- a/net/netfilter/xt_TCPMSS.c
+++ b/net/netfilter/xt_TCPMSS.c
@@ -45,17 +45,22 @@ optlen(const u_int8_t *opt, unsigned int offset)
static int
tcpmss_mangle_packet(struct sk_buff *skb,
- const struct xt_tcpmss_info *info,
+ const struct xt_action_param *par,
unsigned int in_mtu,
unsigned int tcphoff,
unsigned int minlen)
{
+ const struct xt_tcpmss_info *info = par->targinfo;
struct tcphdr *tcph;
unsigned int tcplen, i;
__be16 oldval;
u16 newmss;
u8 *opt;
+ /* This is a fragment, no TCP header is available */
+ if (par->fragoff != 0)
+ return XT_CONTINUE;
+
if (!skb_make_writable(skb, skb->len))
return -1;
@@ -182,7 +187,7 @@ tcpmss_tg4(struct sk_buff *skb, const struct xt_action_param *par)
__be16 newlen;
int ret;
- ret = tcpmss_mangle_packet(skb, par->targinfo,
+ ret = tcpmss_mangle_packet(skb, par,
tcpmss_reverse_mtu(skb, PF_INET),
iph->ihl * 4,
sizeof(*iph) + sizeof(struct tcphdr));
@@ -211,7 +216,7 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par)
tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr, &frag_off);
if (tcphoff < 0)
return NF_DROP;
- ret = tcpmss_mangle_packet(skb, par->targinfo,
+ ret = tcpmss_mangle_packet(skb, par,
tcpmss_reverse_mtu(skb, PF_INET6),
tcphoff,
sizeof(*ipv6h) + sizeof(struct tcphdr));
