netdev - Re: [PATCH v1 net 6/7] tcp: Fix data-races around sysctl_tcp_reflect

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Date:   Fri, 22 Jul 2022 11:58:49 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...nel.org>,
        Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v1 net 6/7] tcp: Fix data-races around sysctl_tcp_reflect_tos.

On Fri, Jul 22, 2022 at 11:24 AM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> While reading sysctl_tcp_reflect_tos, it can be changed concurrently.
> Thus, we need to add READ_ONCE() to its readers.
>
> Fixes: ac8f1710c12b ("tcp: reflect tos value received in SYN to the socket")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> ---

Acked-by: Wei Wang <weiwan@...gle.com>

> CC: Wei Wang <weiwan@...gle.com>
> ---
>  net/ipv4/tcp_ipv4.c | 4 ++--
>  net/ipv6/tcp_ipv6.c | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index d16e6e40f47b..586c102ce152 100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -1006,7 +1006,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
>         if (skb) {
>                 __tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
>
> -               tos = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
> +               tos = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos) ?
>                                 (tcp_rsk(req)->syn_tos & ~INET_ECN_MASK) |
>                                 (inet_sk(sk)->tos & INET_ECN_MASK) :
>                                 inet_sk(sk)->tos;
> @@ -1526,7 +1526,7 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
>         /* Set ToS of the new socket based upon the value of incoming SYN.
>          * ECT bits are set later in tcp_init_transfer().
>          */
> -       if (sock_net(sk)->ipv4.sysctl_tcp_reflect_tos)
> +       if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos))
>                 newinet->tos = tcp_rsk(req)->syn_tos & ~INET_ECN_MASK;
>
>         if (!dst) {
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index 9d3ede293258..be09941fe6d9 100644
> --- a/net/ipv6/tcp_ipv6.c
> +++ b/net/ipv6/tcp_ipv6.c
> @@ -546,7 +546,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
>                 if (np->repflow && ireq->pktopts)
>                         fl6->flowlabel = ip6_flowlabel(ipv6_hdr(ireq->pktopts));
>
> -               tclass = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
> +               tclass = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos) ?
>                                 (tcp_rsk(req)->syn_tos & ~INET_ECN_MASK) |
>                                 (np->tclass & INET_ECN_MASK) :
>                                 np->tclass;
> @@ -1314,7 +1314,7 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
>         /* Set ToS of the new socket based upon the value of incoming SYN.
>          * ECT bits are set later in tcp_init_transfer().
>          */
> -       if (sock_net(sk)->ipv4.sysctl_tcp_reflect_tos)
> +       if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reflect_tos))
>                 newnp->tclass = tcp_rsk(req)->syn_tos & ~INET_ECN_MASK;
>
>         /* Clone native IPv6 options from listening socket (if any)
> --
> 2.30.2
>