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 4.4-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-4.4 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
@@ -502,17 +502,17 @@ 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-4.4/tcp-protect-accesses-to-.ts_recent_stamp-with-read-write-_once.patch
queue-4.4/tcp-fix-rejected-syncookies-due-to-stale-timestamps.patch
queue-4.4/tcp-tighten-acceptance-of-acks-not-matching-a-child-socket.patch
