diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/tcp.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 2424026a6530..2c47947eac07 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -512,7 +512,15 @@ static inline bool tcp_synq_no_recent_overflow(const struct sock *sk) { unsigned long last_overflow = 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) |