From 721c8dafad26ccfa90ff659ee19755e3377b829d Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 6 Dec 2019 12:38:49 +0100 Subject: tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() Syncookies borrow the ->rx_opt.ts_recent_stamp field to store the timestamp of the last synflood. Protect them with READ_ONCE() and WRITE_ONCE() since reads and writes aren't serialised. Use of .rx_opt.ts_recent_stamp for storing the synflood timestamp was introduced by a0f82f64e269 ("syncookies: remove last_synq_overflow from struct tcp_sock"). But unprotected accesses were already there when timestamp was stored in .last_synq_overflow. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Guillaume Nault Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/tcp.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/net') diff --git a/include/net/tcp.h b/include/net/tcp.h index 43e04e14c41e..86b9a8766648 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -501,9 +501,9 @@ static inline void tcp_synq_overflow(const struct sock *sk) } } - last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; + last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp); if (!time_between32(now, last_overflow, last_overflow + HZ)) - tcp_sk(sk)->rx_opt.ts_recent_stamp = now; + WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now); } /* syncookies: no recent synqueue overflow on this listening socket? */ @@ -524,7 +524,7 @@ static inline bool tcp_synq_no_recent_overflow(const struct sock *sk) } } - last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp; + 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 -- cgit v1.2.3