From: Eric Dumazet <eric.dumazet@gmail.com>
To: Jakub Sitnicki <jakub@cloudflare.com>, bpf@vger.kernel.org
Cc: 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 09:18:39 -0800 [thread overview]
Message-ID: <a6bf279e-a998-84ab-4371-cd6c1ccbca5d@gmail.com> (raw)
In-Reply-To: <20200123155534.114313-3-jakub@cloudflare.com>
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:
>
> Read side:
>
> tcp_v4_rcv
> sk = __inet_lookup_skb(...)
> tcp_check_req(sk)
> inet_csk(sk)->icsk_af_ops->syn_recv_sock
> tcp_v4_syn_recv_sock
> tcp_create_openreq_child
> inet_csk_clone_lock
> sk_clone_lock
> READ_ONCE(sk->sk_prot)
>
> Write side:
>
> sock_map_ops->map_update_elem
> sock_map_update_elem
> sock_map_update_common
> sock_map_link_no_progs
> tcp_bpf_init
> tcp_bpf_update_sk_prot
> sk_psock_update_proto
> WRITE_ONCE(sk->sk_prot, ops)
>
> sock_map_ops->map_delete_elem
> sock_map_delete_elem
> __sock_map_delete
> sock_map_unref
> sk_psock_put
> sk_psock_drop
> sk_psock_restore_proto
> tcp_update_ulp
> WRITE_ONCE(sk->sk_prot, proto)
>
> Mark the shared access with READ_ONCE/WRITE_ONCE annotations.
>
> Acked-by: Martin KaFai Lau <kafai@fb.com>
> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
> ---
> 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
const struct proto *ops = READ_ONCE(sk->sk_prot);
if (ops->handler)
ops->handler(....);
next prev parent reply other threads:[~2020-01-23 17:18 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 [this message]
2020-01-23 18:56 ` Jakub Sitnicki
2020-01-23 19:15 ` John Fastabend
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=a6bf279e-a998-84ab-4371-cd6c1ccbca5d@gmail.com \
--to=eric.dumazet@gmail.com \
--cc=bpf@vger.kernel.org \
--cc=jakub@cloudflare.com \
--cc=john.fastabend@gmail.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).