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    Subject[PATCH 4.19 21/62] tcp: Fix a data-race around sysctl_tcp_notsent_lowat.
    Date
    From: Kuniyuki Iwashima <kuniyu@amazon.com>

    [ Upstream commit 55be873695ed8912eb77ff46d1d1cadf028bd0f3 ]

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

    Fixes: c9bee3b7fdec ("tcp: TCP_NOTSENT_LOWAT socket option")
    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>
    ---
    include/net/tcp.h | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/include/net/tcp.h b/include/net/tcp.h
    index f92b93cf074c..9b1bf1567861 100644
    --- a/include/net/tcp.h
    +++ b/include/net/tcp.h
    @@ -1876,7 +1876,7 @@ void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
    static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
    {
    struct net *net = sock_net((struct sock *)tp);
    - return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
    + return tp->notsent_lowat ?: READ_ONCE(net->ipv4.sysctl_tcp_notsent_lowat);
    }

    static inline bool tcp_stream_memory_free(const struct sock *sk)
    --
    2.35.1


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