This is a note to let you know that I've just added the patch titled
tcp: Defer ts_recent changes until req is owned
to the 6.12-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-defer-ts_recent-changes-until-req-is-owned.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit aedefdf20189f92f09ce5354fa2eb23ea07c0d2a
Author: Wang Hai <wanghai38@xxxxxxxxxx>
Date: Mon Feb 24 17:00:47 2025 +0800
tcp: Defer ts_recent changes until req is owned
[ Upstream commit 8d52da23b6c68a0f6bad83959ebb61a2cf623c4e ]
Recently a bug was discovered where the server had entered TCP_ESTABLISHED
state, but the upper layers were not notified.
The same 5-tuple packet may be processed by different CPUSs, so two
CPUs may receive different ack packets at the same time when the
state is TCP_NEW_SYN_RECV.
In that case, req->ts_recent in tcp_check_req may be changed concurrently,
which will probably cause the newsk's ts_recent to be incorrectly large.
So that tcp_validate_incoming will fail. At this point, newsk will not be
able to enter the TCP_ESTABLISHED.
cpu1 cpu2
tcp_check_req
tcp_check_req
req->ts_recent = rcv_tsval = t1
req->ts_recent = rcv_tsval = t2
syn_recv_sock
tcp_sk(child)->rx_opt.ts_recent = req->ts_recent = t2 // t1 < t2
tcp_child_process
tcp_rcv_state_process
tcp_validate_incoming
tcp_paws_check
if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
// t2 - t1 > paws_win, failed
tcp_v4_do_rcv
tcp_rcv_state_process
// TCP_ESTABLISHED
The cpu2's skb or a newly received skb will call tcp_v4_do_rcv to get
the newsk into the TCP_ESTABLISHED state, but at this point it is no
longer possible to notify the upper layer application. A notification
mechanism could be added here, but the fix is more complex, so the
current fix is used.
In tcp_check_req, req->ts_recent is used to assign a value to
tcp_sk(child)->rx_opt.ts_recent, so removing the change in req->ts_recent
and changing tcp_sk(child)->rx_opt.ts_recent directly after owning the
req fixes this bug.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Wang Hai <wanghai38@xxxxxxxxxx>
Reviewed-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index bb1fe1ba867ac..f3e4fc9572196 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -806,12 +806,6 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
/* In sequence, PAWS is OK. */
- /* TODO: We probably should defer ts_recent change once
- * we take ownership of @req.
- */
- if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_nxt))
- WRITE_ONCE(req->ts_recent, tmp_opt.rcv_tsval);
-
if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
/* Truncate SYN, it is out of window starting
at tcp_rsk(req)->rcv_isn + 1. */
@@ -860,6 +854,10 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
if (!child)
goto listen_overflow;
+ if (own_req && tmp_opt.saw_tstamp &&
+ !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_nxt))
+ tcp_sk(child)->rx_opt.ts_recent = tmp_opt.rcv_tsval;
+
if (own_req && rsk_drop_req(req)) {
reqsk_queue_removed(&inet_csk(req->rsk_listener)->icsk_accept_queue, req);
inet_csk_reqsk_queue_drop_and_put(req->rsk_listener, req);
