linux-kernel - [ 46/66] tcp: fix FIONREAD/SIOCINQ

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Date:	Wed, 14 Nov 2012 20:10:51 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Elliot Hughes <enh@...gle.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Tom Herbert <therbert@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 46/66] tcp: fix FIONREAD/SIOCINQ

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

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


From: Eric Dumazet <edumazet@...gle.com>

[ Upstream commit a3374c42aa5f7237e87ff3b0622018636b0c847e ]

tcp_ioctl() tries to take into account if tcp socket received a FIN
to report correct number bytes in receive queue.

But its flaky because if the application ate the last skb,
we return 1 instead of 0.

Correct way to detect that FIN was received is to test SOCK_DONE.

Reported-by: Elliot Hughes <enh@...gle.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>
Cc: Tom Herbert <therbert@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -548,14 +548,12 @@ int tcp_ioctl(struct sock *sk, int cmd,
 			 !tp->urg_data ||
 			 before(tp->urg_seq, tp->copied_seq) ||
 			 !before(tp->urg_seq, tp->rcv_nxt)) {
-			struct sk_buff *skb;
 
 			answ = tp->rcv_nxt - tp->copied_seq;
 
-			/* Subtract 1, if FIN is in queue. */
-			skb = skb_peek_tail(&sk->sk_receive_queue);
-			if (answ && skb)
-				answ -= tcp_hdr(skb)->fin;
+			/* Subtract 1, if FIN was received */
+			if (answ && sock_flag(sk, SOCK_DONE))
+				answ--;
 		} else
 			answ = tp->urg_seq - tp->copied_seq;
 		release_sock(sk);


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