linux-kernel - [PATCH 3.19 020/123] tcp: fix tcp fin memory accounting

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Message-Id: <20150324154424.879590264@linuxfoundation.org>
Date:	Tue, 24 Mar 2015 16:45:29 +0100
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.19 020/123] tcp: fix tcp fin memory accounting

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

------------------

From: Josh Hunt <johunt@...mai.com>

[ Upstream commit d22e1537181188e5dc8cbc51451832625035bdc2 ]

tcp_send_fin() does not account for the memory it allocates properly, so
sk_forward_alloc can be negative in cases where we've sent a FIN:

ss example output (ss -amn | grep -B1 f4294):
tcp    FIN-WAIT-1 0      1            192.168.0.1:45520         192.0.2.1:8080
	skmem:(r0,rb87380,t0,tb87380,f4294966016,w1280,o0,bl0)
Acked-by: Eric Dumazet <edumazet@...gle.com>

Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp_output.c |    6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2775,15 +2775,11 @@ void tcp_send_fin(struct sock *sk)
 	} else {
 		/* Socket is locked, keep trying until memory is available. */
 		for (;;) {
-			skb = alloc_skb_fclone(MAX_TCP_HEADER,
-					       sk->sk_allocation);
+			skb = sk_stream_alloc_skb(sk, 0, sk->sk_allocation);
 			if (skb)
 				break;
 			yield();
 		}
-
-		/* Reserve space for headers and prepare control bits. */
-		skb_reserve(skb, MAX_TCP_HEADER);
 		/* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
 		tcp_init_nondata_skb(skb, tp->write_seq,
 				     TCPHDR_ACK | TCPHDR_FIN);


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