From: Martin Kelly <martin@martingkelly•com>
To: David Miller <davem@davemloft•net>
Cc: netdev@vger•kernel.org,
Paul McKenney <paulmck@linux•vnet.ibm.com>,
Stephen Hemminger <stephen@networkplumber•org>
Subject: Re: Question about synchronize_net() in AF_PACKET close()
Date: Wed, 17 Sep 2014 07:29:27 -0700 [thread overview]
Message-ID: <54199AC7.1040502@martingkelly.com> (raw)
In-Reply-To: <CAN8CM3xEnQXVgrLpV0rfAJoZ75v6Xv64pAGJ-9SAPACAT8WJ_w@mail.gmail.com>
On 09/10/2014 02:37 PM, Martin Kelly wrote:
>> The synchronize_net() is also there to protect against the prot hook
>> which can run asynchronously from the core packet input path on any
>> cpu.
>>
>
> Yes, understood. What I'm not clear about is whether it is safe to do
> the following:
>
> unregister_prot_hook(sk, false);
> sock_orphan(sk);
> sock->sk = NULL;
> call_rcu(...);
> close socket, return to userspace
>
> instead of
>
> unregister_prot_hook(sk, false);
> synchronize_net();
> sock_orphan(sk);
> sock->sk = NULL;
> close socket, return to userspace
>
> If you don't call synchronize_net() immediately, then other readers
> could see the protocol hook in the protocol list and try to use it.
> They could call into prot_hook.func. However, it appears that such
> functions ( e.g. packet_rcv() ) touch the socket buffer but not the
> socket itself, so orphaning the socket before all RCUs have been
> processed is safe. In addition, no new packets will come in after
> packet_release() and touch the socket because the socket fd will be
> removed from the process fd list.
>
> From my testing, I'm not seeing any obvious issues, but I could be
> missing something. Is orphaning the socket before all RCUs have
> finished unsafe?
>
(friendly ping)
next prev parent reply other threads:[~2014-09-17 14:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-09 21:44 Question about synchronize_net() in AF_PACKET close() Martin Kelly
2014-09-09 22:00 ` David Miller
2014-09-10 13:19 ` Marcelo Ricardo Leitner
2014-09-10 21:39 ` Martin Kelly
2014-09-10 21:37 ` Martin Kelly
2014-09-17 14:29 ` Martin Kelly [this message]
2014-09-17 14:54 ` Eric Dumazet
2014-09-17 17:04 ` Martin Kelly
2014-09-17 17:52 ` Eric Dumazet
2014-09-17 18:58 ` Martin Kelly
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=54199AC7.1040502@martingkelly.com \
--to=martin@martingkelly$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=netdev@vger$(echo .)kernel.org \
--cc=paulmck@linux$(echo .)vnet.ibm.com \
--cc=stephen@networkplumber$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox