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    Subject[PATCH 4.19 19/62] tcp: Fix data-races around sysctl_tcp_reordering.
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    [ Upstream commit 46778cd16e6a5ad1b2e3a91f6c057c907379418e ]

    While reading sysctl_tcp_reordering, it can be changed concurrently.
    Thus, we need to add READ_ONCE() to its readers.

    Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/ipv4/tcp.c | 2 +-
    net/ipv4/tcp_input.c | 10 +++++++---
    net/ipv4/tcp_metrics.c | 3 ++-
    3 files changed, 10 insertions(+), 5 deletions(-)

    diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
    index f7795488b0ad..b1b121d5076c 100644
    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -436,7 +436,7 @@ void tcp_init_sock(struct sock *sk)
    tp->snd_cwnd_clamp = ~0;
    tp->mss_cache = TCP_MSS_DEFAULT;

    - tp->reordering = sock_net(sk)->ipv4.sysctl_tcp_reordering;
    + tp->reordering = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reordering);
    tcp_assign_congestion_control(sk);

    tp->tsoffset = 0;
    diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
    index 92f5068c7680..afe195e03a95 100644
    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -1982,6 +1982,7 @@ void tcp_enter_loss(struct sock *sk)
    struct tcp_sock *tp = tcp_sk(sk);
    struct net *net = sock_net(sk);
    bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
    + u8 reordering;

    tcp_timeout_mark_lost(sk);

    @@ -2002,10 +2003,12 @@ void tcp_enter_loss(struct sock *sk)
    /* Timeout in disordered state after receiving substantial DUPACKs
    * suggests that the degree of reordering is over-estimated.
    */
    + reordering = READ_ONCE(net->ipv4.sysctl_tcp_reordering);
    if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
    - tp->sacked_out >= net->ipv4.sysctl_tcp_reordering)
    + tp->sacked_out >= reordering)
    tp->reordering = min_t(unsigned int, tp->reordering,
    - net->ipv4.sysctl_tcp_reordering);
    + reordering);
    +
    tcp_set_ca_state(sk, TCP_CA_Loss);
    tp->high_seq = tp->snd_nxt;
    tcp_ecn_queue_cwr(tp);
    @@ -3303,7 +3306,8 @@ static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)
    * new SACK or ECE mark may first advance cwnd here and later reduce
    * cwnd in tcp_fastretrans_alert() based on more states.
    */
    - if (tcp_sk(sk)->reordering > sock_net(sk)->ipv4.sysctl_tcp_reordering)
    + if (tcp_sk(sk)->reordering >
    + READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_reordering))
    return flag & FLAG_FORWARD_PROGRESS;

    return flag & FLAG_DATA_ACKED;
    diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
    index 03b51cdcc731..61843c6d7a47 100644
    --- a/net/ipv4/tcp_metrics.c
    +++ b/net/ipv4/tcp_metrics.c
    @@ -425,7 +425,8 @@ void tcp_update_metrics(struct sock *sk)
    if (!tcp_metric_locked(tm, TCP_METRIC_REORDERING)) {
    val = tcp_metric_get(tm, TCP_METRIC_REORDERING);
    if (val < tp->reordering &&
    - tp->reordering != net->ipv4.sysctl_tcp_reordering)
    + tp->reordering !=
    + READ_ONCE(net->ipv4.sysctl_tcp_reordering))
    tcp_metric_set(tm, TCP_METRIC_REORDERING,
    tp->reordering);
    }
    --
    2.35.1


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