netdev - Re: [PATCH net] net: memcontrol: charge allocated memory after mem_cgroup_sk

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Message-ID: <20180201202158.GA11477@castle.DHCP.thefacebook.com>
Date:   Thu, 1 Feb 2018 20:22:04 +0000
From:   Roman Gushchin <guro@...com>
To:     Eric Dumazet <edumazet@...gle.com>
CC:     "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <kernel-team@...com>,
        <edumazet@...gle.com>, <hannes@...xchg.org>, <tj@...nel.org>
Subject: Re: [PATCH net] net: memcontrol: charge allocated memory after
 mem_cgroup_sk_alloc()

On Thu, Feb 01, 2018 at 10:16:55AM -0500, David Miller wrote:
> From: Roman Gushchin <guro@...com>
> Date: Wed, 31 Jan 2018 21:54:08 +0000
> 
> > So I really start thinking that reverting 9f1c2674b328
> > ("net: memcontrol: defer call to mem_cgroup_sk_alloc()")
> > and fixing the original issue differently might be easier
> > and a proper way to go. Does it makes sense?
> 
> You'll need to work that out with Eric Dumazet who added the
> change in question which you think we should revert.

Eric,

can you, please, provide some details about the use-after-free problem
that you've fixed with commit 9f1c2674b328 ("net: memcontrol: defer call
to mem_cgroup_sk_alloc()" ? Do you know how to reproduce it?

Deferring mem_cgroup_sk_alloc() breaks socket memory accounting
and makes it much more fragile in general. So, I wonder, if there are
solutions for the use-after-free problem.

Thank you!

Roman