tcp: fix overflow in __tcp_retransmit_skb()

[ 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: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 918ecd7..dd8b5c5 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2097,7 +2097,8 @@ 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)) {