netdev - [ 084/123] batman-adv: fix random jitter calculation

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Message-Id: <20130109201509.395329312@linuxfoundation.org>
Date:	Wed,  9 Jan 2013 12:35:23 -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, Akinobu Mita <akinobu.mita@...il.com>,
	Antonio Quartulli <ordex@...istici.org>,
	Marek Lindner <lindner_marek@...oo.de>,
	Simon Wunderlich <siwu@....tu-chemnitz.de>,
	"David S. Miller" <davem@...emloft.net>,
	b.a.t.m.a.n@...ts.open-mesh.org, netdev@...r.kernel.org
Subject: [ 084/123] batman-adv: fix random jitter calculation

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

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


From: Akinobu Mita <akinobu.mita@...il.com>

[ Upstream commit 143cdd8f33909ff5a153e3f02048738c5964ba26 ]

batadv_iv_ogm_emit_send_time() attempts to calculates a random integer
in the range of 'orig_interval +- BATADV_JITTER' by the below lines.

        msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
        msecs += (random32() % 2 * BATADV_JITTER);

But it actually gets 'orig_interval' or 'orig_interval - BATADV_JITTER'
because '%' and '*' have same precedence and associativity is
left-to-right.

This adds the parentheses at the appropriate position so that it matches
original intension.

Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
Acked-by: Antonio Quartulli <ordex@...istici.org>
Cc: Marek Lindner <lindner_marek@...oo.de>
Cc: Simon Wunderlich <siwu@....tu-chemnitz.de>
Cc: Antonio Quartulli <ordex@...istici.org>
Cc: b.a.t.m.a.n@...ts.open-mesh.org
Cc: "David S. Miller" <davem@...emloft.net>
Cc: netdev@...r.kernel.org
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/batman-adv/bat_iv_ogm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -119,7 +119,7 @@ batadv_iv_ogm_emit_send_time(const struc
 	unsigned int msecs;
 
 	msecs = atomic_read(&bat_priv->orig_interval) - BATADV_JITTER;
-	msecs += (random32() % 2 * BATADV_JITTER);
+	msecs += random32() % (2 * BATADV_JITTER);
 
 	return jiffies + msecs_to_jiffies(msecs);
 }


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