bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: John Fastabend <john.fastabend@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	John Fastabend <john.fastabend@gmail.com>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
	kernel-team@cloudflare.com,
	John Fastabend <john.fastabend@gmail.com>,
	Lorenz Bauer <lmb@cloudflare.com>, Martin Lau <kafai@fb.com>
Subject: Re: [PATCH bpf-next v4 02/12] net, sk_msg: Annotate lockless access to sk_prot on clone
Date: Thu, 23 Jan 2020 11:15:22 -0800	[thread overview]
Message-ID: <5e29f0caaec93_5aac2ad03f6d65c09b@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <874kwm2e8a.fsf@cloudflare.com>

Jakub Sitnicki wrote:
> On Thu, Jan 23, 2020 at 06:18 PM CET, Eric Dumazet wrote:
> > On 1/23/20 7:55 AM, Jakub Sitnicki wrote:
> >> sk_msg and ULP frameworks override protocol callbacks pointer in
> >> sk->sk_prot, while tcp accesses it locklessly when cloning the listening
> >> socket, that is with neither sk_lock nor sk_callback_lock held.
> >>
> >> Once we enable use of listening sockets with sockmap (and hence sk_msg),
> >> there will be shared access to sk->sk_prot if socket is getting cloned
> >> while being inserted/deleted to/from the sockmap from another CPU:

[...]

> >>  include/linux/skmsg.h | 3 ++-
> >>  net/core/sock.c       | 5 +++--
> >>  net/ipv4/tcp_bpf.c    | 4 +++-
> >>  net/ipv4/tcp_ulp.c    | 3 ++-
> >>  net/tls/tls_main.c    | 3 ++-
> >>  5 files changed, 12 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
> >> index 41ea1258d15e..55c834a5c25e 100644
> >> --- a/include/linux/skmsg.h
> >> +++ b/include/linux/skmsg.h
> >> @@ -352,7 +352,8 @@ static inline void sk_psock_update_proto(struct sock *sk,
> >>  	psock->saved_write_space = sk->sk_write_space;
> >>
> >>  	psock->sk_proto = sk->sk_prot;
> >> -	sk->sk_prot = ops;
> >> +	/* Pairs with lockless read in sk_clone_lock() */
> >> +	WRITE_ONCE(sk->sk_prot, ops);
> >
> >
> > Note there are dozens of calls like
> >
> > if (sk->sk_prot->handler)
> >     sk->sk_prot->handler(...);
> >
> > Some of them being done lockless.
> >
> > I know it is painful, but presumably we need

Correct.

> >
> > const struct proto *ops = READ_ONCE(sk->sk_prot);
> >
> > if (ops->handler)
> >     ops->handler(....);
> 
> Yikes! That will be quite an audit. Thank you for taking a look.
> 
> Now I think I understand what John had in mind when asking for pushing
> these annotations to the bpf tree as well [0].

Yep this is what I meant. But your patches don't make the situation
any worse its already there.

> 
> Considering these are lacking today, can I do it as a follow up?

In my opinion yes. I think pulling your patches in is OK and I started
doing this conversion already so we can have a fix shortly. I didn't
want to push it into rc7 though so I'll push it next week or into
net-next tree.

.John

  reply	other threads:[~2020-01-23 19:15 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-23 15:55 [PATCH bpf-next v4 00/12] Extend SOCKMAP to store listening sockets Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 01/12] bpf, sk_msg: Don't clear saved sock proto on restore Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 02/12] net, sk_msg: Annotate lockless access to sk_prot on clone Jakub Sitnicki
2020-01-23 17:18   ` Eric Dumazet
2020-01-23 18:56     ` Jakub Sitnicki
2020-01-23 19:15       ` John Fastabend [this message]
2020-01-27  9:36         ` Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 03/12] net, sk_msg: Clear sk_user_data pointer on clone if tagged Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 04/12] tcp_bpf: Don't let child socket inherit parent protocol ops on copy Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 05/12] bpf, sockmap: Allow inserting listening TCP sockets into sockmap Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 06/12] bpf, sockmap: Don't set up sockmap progs for listening sockets Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 07/12] bpf, sockmap: Return socket cookie on lookup from syscall Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 08/12] bpf, sockmap: Let all kernel-land lookup values in SOCKMAP Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 09/12] bpf: Allow selecting reuseport socket from a SOCKMAP Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 10/12] net: Generate reuseport group ID on group creation Jakub Sitnicki
2020-01-23 17:02   ` Martin Lau
2020-01-23 15:55 ` [PATCH bpf-next v4 11/12] selftests/bpf: Extend SK_REUSEPORT tests to cover SOCKMAP Jakub Sitnicki
2020-01-23 15:55 ` [PATCH bpf-next v4 12/12] selftests/bpf: Tests for SOCKMAP holding listening sockets Jakub Sitnicki
2020-01-27 11:13 ` [PATCH bpf-next v4 00/12] Extend SOCKMAP to store " Daniel Borkmann
2020-01-27 13:03   ` Jakub Sitnicki

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=5e29f0caaec93_5aac2ad03f6d65c09b@john-XPS-13-9370.notmuch \
    --to=john.fastabend@gmail.com \
    --cc=bpf@vger.kernel.org \
    --cc=eric.dumazet@gmail.com \
    --cc=jakub@cloudflare.com \
    --cc=kafai@fb.com \
    --cc=kernel-team@cloudflare.com \
    --cc=lmb@cloudflare.com \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).