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    Subject[PATCH 3.12 084/127] tcp: fix overflow in __tcp_retransmit_skb()
    Date
    From: Eric Dumazet <edumazet@google.com>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    [ Upstream commit ffb4d6c8508657824bcef68a36b2a0f9d8c09d10 ]

    If a TCP socket gets a large write queue, an overflow can happen
    in a test in __tcp_retransmit_skb() preventing all retransmits.

    The flow then stalls and resets after timeouts.

    Tested:

    sysctl -w net.core.wmem_max=1000000000
    netperf -H dest -- -s 1000000000

    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    net/ipv4/tcp_output.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
    index aa72c9d604a0..f08921156be8 100644
    --- a/net/ipv4/tcp_output.c
    +++ b/net/ipv4/tcp_output.c
    @@ -2336,7 +2336,8 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
    * copying overhead: fragmentation, tunneling, mangling etc.
    */
    if (atomic_read(&sk->sk_wmem_alloc) >
    - min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
    + min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
    + sk->sk_sndbuf))
    return -EAGAIN;

    if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
    --
    2.10.2
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