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    Subject[PATCH 5.15 123/201] tcp: Fix data-races around sysctl_tcp_recovery.
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    [ Upstream commit e7d2ef837e14a971a05f60ea08c47f3fed1a36e4 ]

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

    Fixes: 4f41b1c58a32 ("tcp: use RACK to detect losses")
    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_input.c | 3 ++-
    net/ipv4/tcp_recovery.c | 6 ++++--
    2 files changed, 6 insertions(+), 3 deletions(-)

    diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
    index dd10a317709f..1cc0aca39c04 100644
    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -2087,7 +2087,8 @@ static inline void tcp_init_undo(struct tcp_sock *tp)

    static bool tcp_is_rack(const struct sock *sk)
    {
    - return sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION;
    + return READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
    + TCP_RACK_LOSS_DETECTION;
    }

    /* If we detect SACK reneging, forget all SACK information
    diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
    index fd113f6226ef..ac14216f6204 100644
    --- a/net/ipv4/tcp_recovery.c
    +++ b/net/ipv4/tcp_recovery.c
    @@ -19,7 +19,8 @@ static u32 tcp_rack_reo_wnd(const struct sock *sk)
    return 0;

    if (tp->sacked_out >= tp->reordering &&
    - !(sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_NO_DUPTHRESH))
    + !(READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
    + TCP_RACK_NO_DUPTHRESH))
    return 0;
    }

    @@ -192,7 +193,8 @@ void tcp_rack_update_reo_wnd(struct sock *sk, struct rate_sample *rs)
    {
    struct tcp_sock *tp = tcp_sk(sk);

    - if (sock_net(sk)->ipv4.sysctl_tcp_recovery & TCP_RACK_STATIC_REO_WND ||
    + if ((READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_recovery) &
    + TCP_RACK_STATIC_REO_WND) ||
    !rs->prior_delivered)
    return;

    --
    2.35.1


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