diff options
| -rw-r--r-- | include/linux/time.h | 13 | ||||
| -rw-r--r-- | include/net/tcp.h | 27 |
2 files changed, 32 insertions, 8 deletions
diff --git a/include/linux/time.h b/include/linux/time.h index 0760a4f5a15c..8e10b9dbd8c2 100644 --- a/include/linux/time.h +++ b/include/linux/time.h @@ -97,4 +97,17 @@ static inline bool itimerspec64_valid(const struct itimerspec64 *its) */ #define time_after32(a, b) ((s32)((u32)(b) - (u32)(a)) < 0) #define time_before32(b, a) time_after32(a, b) + +/** + * time_between32 - check if a 32-bit timestamp is within a given time range + * @t: the time which may be within [l,h] + * @l: the lower bound of the range + * @h: the higher bound of the range + * + * time_before32(t, l, h) returns true if @l <= @t <= @h. All operands are + * treated as 32-bit integers. + * + * Equivalent to !(time_before32(@t, @l) || time_after32(@t, @h)). + */ +#define time_between32(t, l, h) ((u32)(h) - (u32)(l) >= (u32)(t) - (u32)(l)) #endif diff --git a/include/net/tcp.h b/include/net/tcp.h index 36f195fb576a..86b9a8766648 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -494,15 +494,16 @@ static inline void tcp_synq_overflow(const struct sock *sk) reuse = rcu_dereference(sk->sk_reuseport_cb); if (likely(reuse)) { last_overflow = READ_ONCE(reuse->synq_overflow_ts); - if (time_after32(now, last_overflow + HZ)) + if (!time_between32(now, last_overflow, + last_overflow + HZ)) WRITE_ONCE(reuse->synq_overflow_ts, now); return; } } - last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; - if (time_after32(now, last_overflow + HZ)) - tcp_sk(sk)->rx_opt.ts_recent_stamp = now; + last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp); + 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? */ @@ -517,13 +518,23 @@ static inline bool tcp_synq_no_recent_overflow(const struct sock *sk) reuse = rcu_dereference(sk->sk_reuseport_cb); if (likely(reuse)) { last_overflow = READ_ONCE(reuse->synq_overflow_ts); - return time_after32(now, last_overflow + - TCP_SYNCOOKIE_VALID); + return !time_between32(now, last_overflow - HZ, + last_overflow + + TCP_SYNCOOKIE_VALID); } } - last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; - return time_after32(now, last_overflow + TCP_SYNCOOKIE_VALID); + last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp); + + /* 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(now, last_overflow - HZ, + last_overflow + TCP_SYNCOOKIE_VALID); } static inline u32 tcp_cookie_time(void) |