This is a note to let you know that I've just added the patch titled tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: tcp-protect-accesses-to-.ts_recent_stamp-with-read-write-_once.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Tue 17 Dec 2019 09:44:32 PM CET From: Guillaume Nault <gnault@xxxxxxxxxx> Date: Fri, 6 Dec 2019 12:38:49 +0100 Subject: tcp: Protect accesses to .ts_recent_stamp with {READ,WRITE}_ONCE() From: Guillaume Nault <gnault@xxxxxxxxxx> [ Upstream commit 721c8dafad26ccfa90ff659ee19755e3377b829d ] 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 <gnault@xxxxxxxxxx> Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- include/net/tcp.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -494,17 +494,17 @@ struct sock *cookie_v4_check(struct sock */ 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_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? */ 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); /* If last_overflow <= jiffies <= last_overflow + TCP_SYNCOOKIE_VALID, * then we're under synflood. However, we have to use Patches currently in stable-queue which might be from gnault@xxxxxxxxxx are queue-4.9/tcp-protect-accesses-to-.ts_recent_stamp-with-read-write-_once.patch queue-4.9/tcp-fix-rejected-syncookies-due-to-stale-timestamps.patch queue-4.9/tcp-tighten-acceptance-of-acks-not-matching-a-child-socket.patch