[TCP]: Reset gso_segs if packet is dodgy

I wasn't paranoid enough in verifying GSO information.  A bogus gso_segs
could upset drivers as much as a bogus header would.  Let's reset it in
the per-protocol gso_segment functions.

I didn't verify gso_size because that can be verified by the source of
the dodgy packets.

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

1 files changed, 10 insertions, 4 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 0336422c88a0..0bb0ac96d675 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2166,13 +2166,19 @@ struct sk_buff *tcp_tso_segment(struct sk_buff *skb, int features)
         if (!pskb_may_pull(skb, thlen))
                 goto out;
 
-        segs = NULL;
-        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST))
-                goto out;
-
         oldlen = (u16)~skb->len;
         __skb_pull(skb, thlen);
 
+        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
+                /* Packet is from an untrusted source, reset gso_segs. */
+                int mss = skb_shinfo(skb)->gso_size;
+
+                skb_shinfo(skb)->gso_segs = (skb->len + mss - 1) / mss;
+
+                segs = NULL;
+                goto out;
+        }
+
         segs = skb_segment(skb, features);
         if (IS_ERR(segs))
                 goto out;