Merge tag 'v4.4.207' into 10

[sagit-ice-cold/kernel_xiaomi_msm8998.git] / include / net / tcp.h

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 3330b90..7a58ee2 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -518,19 +518,27 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
  */
 static inline void tcp_synq_overflow(const struct sock *sk)
 {
-       unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+       unsigned long last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
        unsigned long now = jiffies;
 
-       if (time_after(now, last_overflow + HZ))
-               tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
+       if (!time_between32(now, last_overflow, last_overflow + HZ))
+               WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now);
 }
 
 /* syncookies: no recent synqueue overflow on this listening socket? */
 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
 {
-       unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+       unsigned long last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
 
-       return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
+       /* If last_overflow <= jiffies <= last_overflow + TCP_SYNCOOKIE_VALID,
+        * then we're under synflood. However, we have to use
+        * 'last_overflow - HZ' as lower bound. That's because a concurrent
+        * tcp_synq_overflow() could update .ts_recent_stamp after we read
+        * jiffies but before we store .ts_recent_stamp into last_overflow,
+        * which could lead to rejecting a valid syncookie.
+        */
+       return !time_between32(jiffies, last_overflow - HZ,
+                              last_overflow + TCP_SYNCOOKIE_VALID);
 }
 
 static inline u32 tcp_cookie_time(void)