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    Subject[PATCH 5.4 36/87] tcp: Fix a data-race around sysctl_tcp_tw_reuse.
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    [ Upstream commit cbfc6495586a3f09f6f07d9fb3c7cafe807e3c55 ]

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

    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_ipv4.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
    index 72fe93ace7d7..b95e1a3487c8 100644
    --- a/net/ipv4/tcp_ipv4.c
    +++ b/net/ipv4/tcp_ipv4.c
    @@ -105,10 +105,10 @@ static u32 tcp_v4_init_ts_off(const struct net *net, const struct sk_buff *skb)

    int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
    {
    + int reuse = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tw_reuse);
    const struct inet_timewait_sock *tw = inet_twsk(sktw);
    const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
    struct tcp_sock *tp = tcp_sk(sk);
    - int reuse = sock_net(sk)->ipv4.sysctl_tcp_tw_reuse;

    if (reuse == 2) {
    /* Still does not detect *everything* that goes through
    --
    2.35.1


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