netdev - Re: [PATCH bpf-next] net: Fix slab-out-of-bounds in inet[6]_steal

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Date: Wed, 9 Aug 2023 10:14:51 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <lmb@...valent.com>
CC: <bpf@...r.kernel.org>, <daniel@...earbox.net>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <kuniyu@...zon.com>,
	<linux-kernel@...r.kernel.org>, <martin.lau@...nel.org>,
	<martin.lau@...ux.dev>, <memxor@...il.com>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>
Subject: Re: [PATCH bpf-next] net: Fix slab-out-of-bounds in inet[6]_steal_sock

From: Lorenz Bauer <lmb@...valent.com>
Date: Wed, 9 Aug 2023 17:55:02 +0100
> On Wed, Aug 9, 2023 at 4:56 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
> >
> > > Things we could do if necessary:
> > > 1. Reset the flag in inet_csk_clone_lock like we do for SOCK_RCU_FREE
> >
> > I think we can't do this as sk_reuseport is inherited to twsk and used
> > in inet_bind_conflict().
> 
> Ok, so what kind of state does reuseport carry in the various states then?
> 
> TCP_LISTEN: sk_reuseport && sk_reuseport_cb
> TCP_ESTABLISHED: sk_reuseport && !sk_reuseport_cb
> TCP_TIME_WAIT: sk_reuseport && !sk_reuseport_cb
> 
> Where is sk_reuseport_cb cleared? On clone? Or not at all?

sk_clone_lock() does when cloning sk from listener, and we
cannot check sk_reuseport_cb for twsk as it doesn't have the
member.


> 
> > > 2. Duplicate the cb check into inet[6]_steal_sock
> >
> > or 3. Add sk_fullsock() test ?
> 
> I guess this would be in addition to the convoluted series of checks
> I've removed in this patch?

Yes.