3 files changed, 22 insertions, 9 deletions

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 9e68e25c8b82..18c246c9b009 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -464,7 +464,7 @@ extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb,
                                      __u16 *mss);
 
 extern __u32 cookie_init_timestamp(struct request_sock *req);
-extern void cookie_check_timestamp(struct tcp_options_received *tcp_opt);
+extern bool cookie_check_timestamp(struct tcp_options_received *tcp_opt);
 
 /* From net/ipv6/syncookies.c */
 extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 02bef6aa8b30..51b5662545d6 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -230,23 +230,36 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
  * The lowest 4 bits are for snd_wscale
  * The next 4 lsb are for rcv_wscale
  * The next lsb is for sack_ok
+ *
+ * return false if we decode an option that should not be.
  */
-void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
+bool cookie_check_timestamp(struct tcp_options_received *tcp_opt)
 {
         /* echoed timestamp, 9 lowest bits contain options */
         u32 options = tcp_opt->rcv_tsecr & TSMASK;
 
+        if (!tcp_opt->saw_tstamp)  {
+                tcp_clear_options(tcp_opt);
+                return true;
+        }
+
+        if (!sysctl_tcp_timestamps)
+                return false;
+
         tcp_opt->snd_wscale = options & 0xf;
         options >>= 4;
         tcp_opt->rcv_wscale = options & 0xf;
 
         tcp_opt->sack_ok = (options >> 4) & 0x1;
 
-        if (tcp_opt->sack_ok)
-                tcp_sack_reset(tcp_opt);
+        if (tcp_opt->sack_ok && !sysctl_tcp_sack)
+                return false;
 
-        if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
+        if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale) {
                 tcp_opt->wscale_ok = 1;
+                return sysctl_tcp_window_scaling != 0;
+        }
+        return true;
 }
 EXPORT_SYMBOL(cookie_check_timestamp);
 
@@ -281,8 +294,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
         memset(&tcp_opt, 0, sizeof(tcp_opt));
         tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
 
-        if (tcp_opt.saw_tstamp)
-                cookie_check_timestamp(&tcp_opt);
+        if (!cookie_check_timestamp(&tcp_opt))
+                goto out;
 
         ret = NULL;
         req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 70d330f8c990..c7ee57421ece 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -180,8 +180,8 @@ struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb)
         memset(&tcp_opt, 0, sizeof(tcp_opt));
         tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
 
-        if (tcp_opt.saw_tstamp)
-                cookie_check_timestamp(&tcp_opt);
+        if (!cookie_check_timestamp(&tcp_opt))
+                goto out;
 
         ret = NULL;
         req = inet6_reqsk_alloc(&tcp6_request_sock_ops);