netdev - Re: [TEST] TCP MD5 vs kmemleak

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Date: Thu, 20 Jun 2024 10:02:40 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Dmitry Safonov <0x7f454c46@...il.com>
Cc: Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	rcu@...r.kernel.org
Subject: Re: [TEST] TCP MD5 vs kmemleak

On Wed, Jun 19, 2024 at 01:33:36AM +0100, Dmitry Safonov wrote:
> On Tue, 18 Jun 2024 at 18:47, Paul E. McKenney <paulmck@...nel.org> wrote:
> >
> > On Tue, Jun 18, 2024 at 10:02:10AM -0700, Jakub Kicinski wrote:
> > > On Tue, 18 Jun 2024 09:42:35 -0700 Paul E. McKenney wrote:
> [..]
> > >
> > > Dmitry mentioned this commit, too, but we use the same config for MPTCP
> > > tests, and while we repro TCP AO failures quite frequently, mptcp
> > > doesn't seem to have failed once.
> [..]
> > >
> > > To be clear I think Dmitry was suspecting kfree_rcu(), he mentioned
> > > call_rcu() as something he was expecting to have a similar issue but
> > > it in fact appeared immune.
> >
> > Whew!!!  ;-)
> 
> I'm sorry guys, that was me being inadequate.

I know that feeling!

> That's a real issue, rather than a false-positive:
> https://lore.kernel.org/netdev/20240619-tcp-ao-required-leak-v1-1-6408f3c94247@gmail.com/

So we need call_rcu() to mark memory flowing through it?  If so, we
need help from callers of call_rcu() in the case where more than one
object is being freed.

							Thanx, Paul