From: Tom Parkin <tparkin@katalix.com>
To: Guillaume Nault <gnault@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>,
netdev@vger.kernel.org, g.nault@alphalink.fr,
Cong Wang <cong.wang@bytedance.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Jakub Sitnicki <jakub@cloudflare.com>,
Eric Dumazet <edumazet@google.com>
Subject: Re: [Patch net 1/2] l2tp: convert l2tp_tunnel_list to idr
Date: Mon, 9 Jan 2023 09:55:06 +0000 [thread overview]
Message-ID: <20230109095506.GA29862@katalix.com> (raw)
In-Reply-To: <Y7nMo02WWWwoGmv0@debian>
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On Sat, Jan 07, 2023 at 20:48:51 +0100, Guillaume Nault wrote:
> On Thu, Jan 05, 2023 at 11:13:38AM -0800, Cong Wang wrote:
> > +int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id,
> > + u32 peer_tunnel_id, struct l2tp_tunnel_cfg *cfg,
> > + struct l2tp_tunnel **tunnelp)
> > {
> > struct l2tp_tunnel *tunnel = NULL;
> > int err;
> > enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
> > + struct l2tp_net *pn = l2tp_pernet(net);
> >
> > if (cfg)
> > encap = cfg->encap;
> >
> > + spin_lock_bh(&pn->l2tp_tunnel_idr_lock);
> > + err = idr_alloc_u32(&pn->l2tp_tunnel_idr, NULL, &tunnel_id, tunnel_id,
> > + GFP_ATOMIC);
> > + if (err) {
> > + spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
> > + return err;
> > + }
> > + spin_unlock_bh(&pn->l2tp_tunnel_idr_lock);
>
> Why reserving the tunnel_id in l2tp_tunnel_create()? This function is
> supposed to just allocate a structure and pre-initialise some fields.
> The only cleanup required upon error after this call is to kfree() the
> new structure. So I can't see any reason to guarantee the id will be
> accepted by the future l2tp_tunnel_register() call.
>
> Looks like you could reserve the id at the beginning of
> l2tp_tunnel_register() instead. That'd avoid changing the API and thus
> the side effects on l2tp_{ppp,netlink}.c. Also we wouldn't need create
> l2tp_tunnel_remove().
>
FWIW I also think that'd make more sense, and leave callsites will
less tidyup to do on behalf of l2tp_core.
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next prev parent reply other threads:[~2023-01-09 10:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-05 19:13 [Patch net 0/2] l2tp: fix race conditions in l2tp_tunnel_register() Cong Wang
2023-01-05 19:13 ` [Patch net 1/2] l2tp: convert l2tp_tunnel_list to idr Cong Wang
2023-01-07 18:25 ` Saeed Mahameed
2023-01-07 19:48 ` Cong Wang
2023-01-07 19:48 ` Guillaume Nault
2023-01-09 9:55 ` Tom Parkin [this message]
2023-01-10 6:49 ` Cong Wang
2023-01-05 19:13 ` [Patch net 2/2] l2tp: close all race conditions in l2tp_tunnel_register() Cong Wang
2023-01-07 18:41 ` Saeed Mahameed
2023-01-07 19:52 ` Cong Wang
2023-01-10 1:36 ` Jakub Kicinski
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