From: David Miller <davem@davemloft.net>
To: g.nault@alphalink.fr
Cc: netdev@vger.kernel.org, jchapman@katalix.com
Subject: Re: [PATCH net 1/3] l2tp: hold reference on tunnels in netlink dumps
Date: Fri, 13 Apr 2018 12:15:25 -0400 (EDT) [thread overview]
Message-ID: <20180413.121525.1987403291146818781.davem@davemloft.net> (raw)
In-Reply-To: <20180413160912.GA1405@alphalink.fr>
From: Guillaume Nault <g.nault@alphalink.fr>
Date: Fri, 13 Apr 2018 18:09:12 +0200
> On Fri, Apr 13, 2018 at 10:57:03AM -0400, David Miller wrote:
>> From: Guillaume Nault <g.nault@alphalink.fr>
>> Date: Thu, 12 Apr 2018 20:50:33 +0200
>>
>> > l2tp_tunnel_find_nth() is unsafe: no reference is held on the returned
>> > tunnel, therefore it can be freed whenever the caller uses it.
>> > This patch defines l2tp_tunnel_get_nth() which works similarly, but
>> > also takes a reference on the returned tunnel. The caller then has to
>> > drop it after it stops using the tunnel.
>> >
>> > Convert netlink dumps to make them safe against concurrent tunnel
>> > deletion.
>> >
>> > Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
>> > Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
>>
>> During the entire invocation of l2tp_nl_cmd_tunnel_dump(), the RTNL
>> mutex is held.
>>
>> Therefore no tunnel configuration changes may occur and the tunnel
>> object will persist and is safe to access.
>>
> Yes, but only for updates done with the genl API. For L2TPv2, the
> tunnel can be created by connecting a PPPOL2TP and a UDP socket.
> Closing these sockets destroys the tunnel without any RTNL
> synchronisation.
Right, that's the part I missed. Thanks for explaining.
next prev parent reply other threads:[~2018-04-13 16:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-12 18:50 [PATCH net 0/3] l2tp: remove unsafe calls to l2tp_tunnel_find_nth() Guillaume Nault
2018-04-12 18:50 ` [PATCH net 1/3] l2tp: hold reference on tunnels in netlink dumps Guillaume Nault
2018-04-13 14:57 ` David Miller
2018-04-13 16:09 ` Guillaume Nault
2018-04-13 16:15 ` David Miller [this message]
2018-04-12 18:50 ` [PATCH net 2/3] l2tp: hold reference on tunnels printed in pppol2tp proc file Guillaume Nault
2018-04-12 18:50 ` [PATCH net 3/3] l2tp: hold reference on tunnels printed in l2tp/tunnels debugfs file Guillaume Nault
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