[IPV4] raw: Strengthen check on validity of iph->ihl

We currently check that iph->ihl is bounded by the real length and that
the real length is greater than the minimum IP header length.  However,
we did not check the caes where iph->ihl is less than the minimum IP
header length.

This breaks because some ip_fast_csum implementations assume that which
is quite reasonable.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/ipv4/raw.c b/net/ipv4/raw.c
index 66b42f547bf..e7050f8eabe 100644
--- a/net/ipv4/raw.c
+++ b/net/ipv4/raw.c
@@ -271,6 +271,7 @@ static int raw_send_hdrinc(struct sock *sk, void *from, size_t length,
         int hh_len;
         struct iphdr *iph;
         struct sk_buff *skb;
+        unsigned int iphlen;
         int err;
 
         if (length > rt->u.dst.dev->mtu) {
@@ -304,7 +305,8 @@ static int raw_send_hdrinc(struct sock *sk, void *from, size_t length,
                 goto error_fault;
 
         /* We don't modify invalid header */
-        if (length >= sizeof(*iph) && iph->ihl * 4U <= length) {
+        iphlen = iph->ihl * 4;
+        if (iphlen >= sizeof(*iph) && iphlen <= length) {
                 if (!iph->saddr)
                         iph->saddr = rt->rt_src;
                 iph->check   = 0;