diff options
Diffstat (limited to 'include/net/tcp.h')
| -rw-r--r-- | include/net/tcp.h | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index e9b705a4f66e..d4a26c60ab5a 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -503,19 +503,27 @@ 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) |