From: Ivan Vecera <ivecera@redhat.com>
Date: Wed, 21 Jan 2009 16:30:54 +0100
Subject: [net] tcp-lp: prevent chance for oops
Message-id: 1232551854-30638-1-git-send-email-ivecera@redhat.com
O-Subject: [RHEL5 PATCH] [net] tcp-lp: prevent chance for oops
Bugzilla: 478638
RH-Acked-by: Jiri Pirko <jpirko@redhat.com>
RH-Acked-by: David Miller <davem@redhat.com>

BZs:
#478638 - kernel-2.6.18-92.1.22.el5 misses bug fix which has to be backported.

Description:
This patch addresses the situation when tcp_lp_remote_hz_estimator
incorrectly sets LP_VALID_RHZ flag and returns 0. This causes 'divide
error' and the system hangs.

Test status:
Tested successfully.

Upstream status:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=bfbea8a8869a0e21b97605841d04190d63665d19

Signed-off-by: Ivan Vecera <ivecera@redhat.com>

diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c
index 649ebae..dc44f4d 100644
--- a/net/ipv4/tcp_lp.c
+++ b/net/ipv4/tcp_lp.c
@@ -164,7 +164,7 @@ static u32 tcp_lp_remote_hz_estimator(struct sock *sk)
 
  out:
 	/* record time for successful remote HZ calc */
-	if (rhz > 0)
+	if ((rhz >> 6) > 0)
 		lp->flag |= LP_VALID_RHZ;
 	else
 		lp->flag &= ~LP_VALID_RHZ;