netdev - Re: [PATCH net v4 0/3] tcp: fix handling of stale syncookies timestamps

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Date:   Fri, 06 Dec 2019 21:06:14 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     gnault@...hat.com
Cc:     jakub.kicinski@...ronome.com, netdev@...r.kernel.org,
        edumazet@...gle.com, arnd@...db.de, john.stultz@...aro.org,
        tglx@...utronix.de
Subject: Re: [PATCH net v4 0/3] tcp: fix handling of stale syncookies
 timestamps

From: Guillaume Nault <gnault@...hat.com>
Date: Fri, 6 Dec 2019 12:38:26 +0100

> The synflood timestamps (->ts_recent_stamp and ->synq_overflow_ts) are
> only refreshed when the syncookie protection triggers. Therefore, their
> value can become very far apart from jiffies if no synflood happens for
> a long time.
> 
> If jiffies grows too much and wraps while the synflood timestamp isn't
> refreshed, then time_after32() might consider the later to be in the
> future. This can trick tcp_synq_no_recent_overflow() into returning
> erroneous values and rejecting valid ACKs.
> 
> Patch 1 handles the case of ACKs using legitimate syncookies.
> Patch 2 handles the case of stray ACKs.
> Patch 3 annotates lockless timestamp operations with READ_ONCE() and
> WRITE_ONCE().
 ...

Series applied, thanks.