From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jakub Kicinski <kubakici@wp.pl>,
davem@davemloft.net, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next 3/3] tap: XDP support
Date: Fri, 28 Jul 2017 11:50:45 +0800 [thread overview]
Message-ID: <a53d61f5-584c-db8a-be1f-ddec0666d7df@redhat.com> (raw)
In-Reply-To: <20170728064603-mutt-send-email-mst@kernel.org>
On 2017年07月28日 11:46, Michael S. Tsirkin wrote:
> On Fri, Jul 28, 2017 at 11:28:54AM +0800, Jason Wang wrote:
>>>> + old_prog = rtnl_dereference(tun->xdp_prog);
>>>> + if (old_prog)
>>>> + bpf_prog_put(old_prog);
>>>> + rcu_assign_pointer(tun->xdp_prog, prog);
>>> Is this OK? Could this lead to the program getting freed and then
>>> datapath accessing a stale pointer? I mean in the scenario where the
>>> process gets pre-empted between the bpf_prog_put() and
>>> rcu_assign_pointer()?
>> Will call bpf_prog_put() after rcu_assign_pointer().
> I suspect you need to sync RCU or something before that.
__bpf_prog_put() will do call_rcu(), so looks like it was ok.
Thanks
next prev parent reply other threads:[~2017-07-28 3:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-27 9:25 [PATCH net-next 0/3] XDP support for tap Jason Wang
2017-07-27 9:25 ` [PATCH net-next 1/3] tap: use build_skb() for small packet Jason Wang
2017-07-27 9:25 ` [PATCH net-next 2/3] net: export some generic xdp helpers Jason Wang
2017-07-27 9:25 ` [PATCH net-next 3/3] tap: XDP support Jason Wang
2017-07-28 3:13 ` Jakub Kicinski
2017-07-28 3:28 ` Jason Wang
2017-07-28 3:46 ` Michael S. Tsirkin
2017-07-28 3:50 ` Jason Wang [this message]
2017-07-28 4:05 ` Michael S. Tsirkin
2017-07-28 3:51 ` Jakub Kicinski
2017-07-28 15:11 ` Daniel Borkmann
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