netfilter: tcpmss, optstrip: prefer skb_ensure_writable

This also changes optstrip to only make the tcp header writeable
rather than the entire packet.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c
index 98efb202f8b4a14d329df1cc4614ac4088fbf151..3e24443ab81c3a7dbd77cdfcface4614c4c1efe7 100644 (file)
--- a/net/netfilter/xt_TCPMSS.c
+++ b/net/netfilter/xt_TCPMSS.c
@@ -89,7 +89,7 @@ tcpmss_mangle_packet(struct sk_buff *skb,
        if (par->fragoff != 0)
                return 0;
 
-       if (!skb_make_writable(skb, skb->len))
+       if (skb_ensure_writable(skb, skb->len))
                return -1;
 
        len = skb->len - tcphoff;

diff --git a/net/netfilter/xt_TCPOPTSTRIP.c b/net/netfilter/xt_TCPOPTSTRIP.c
index eb92bffff11ccb22690ec0cf76ff25076d6a8cb6..5a274813076a7b8630e5b03ee43b793a3feef27f 100644 (file)
--- a/net/netfilter/xt_TCPOPTSTRIP.c
+++ b/net/netfilter/xt_TCPOPTSTRIP.c
@@ -31,33 +31,33 @@ static inline unsigned int optlen(const u_int8_t *opt, unsigned int offset)
 static unsigned int
 tcpoptstrip_mangle_packet(struct sk_buff *skb,
                          const struct xt_action_param *par,
-                         unsigned int tcphoff, unsigned int minlen)
+                         unsigned int tcphoff)
 {
        const struct xt_tcpoptstrip_target_info *info = par->targinfo;
+       struct tcphdr *tcph, _th;
        unsigned int optl, i, j;
-       struct tcphdr *tcph;
        u_int16_t n, o;
        u_int8_t *opt;
-       int len, tcp_hdrlen;
+       int tcp_hdrlen;
 
        /* This is a fragment, no TCP header is available */
        if (par->fragoff != 0)
                return XT_CONTINUE;
 
-       if (!skb_make_writable(skb, skb->len))
+       tcph = skb_header_pointer(skb, tcphoff, sizeof(_th), &_th);
+       if (!tcph)
                return NF_DROP;
 
-       len = skb->len - tcphoff;
-       if (len < (int)sizeof(struct tcphdr))
-               return NF_DROP;
-
-       tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
        tcp_hdrlen = tcph->doff * 4;
+       if (tcp_hdrlen < sizeof(struct tcphdr))
+               return NF_DROP;
 
-       if (len < tcp_hdrlen)
+       if (skb_ensure_writable(skb, tcphoff + tcp_hdrlen))
                return NF_DROP;
 
-       opt  = (u_int8_t *)tcph;
+       /* must reload tcph, might have been moved */
+       tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
+       opt  = (u8 *)tcph;
 
        /*
         * Walk through all TCP options - if we find some option to remove,
@@ -91,8 +91,7 @@ tcpoptstrip_mangle_packet(struct sk_buff *skb,
 static unsigned int
 tcpoptstrip_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
-       return tcpoptstrip_mangle_packet(skb, par, ip_hdrlen(skb),
-              sizeof(struct iphdr) + sizeof(struct tcphdr));
+       return tcpoptstrip_mangle_packet(skb, par, ip_hdrlen(skb));
 }
 
 #if IS_ENABLED(CONFIG_IP6_NF_MANGLE)
@@ -109,8 +108,7 @@ tcpoptstrip_tg6(struct sk_buff *skb, const struct xt_action_param *par)
        if (tcphoff < 0)
                return NF_DROP;
 
-       return tcpoptstrip_mangle_packet(skb, par, tcphoff,
-              sizeof(*ipv6h) + sizeof(struct tcphdr));
+       return tcpoptstrip_mangle_packet(skb, par, tcphoff);
 }
 #endif