linux-kernel - [34/40] igmp: Avoid zero delay when receiving odd mixture of IGMP queries

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Date:	Tue, 10 Jan 2012 13:45:47 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Ben Hutchings <ben@...adent.org.uk>,
	"David S. Miller" <davem@...emloft.net>
Subject: [34/40] igmp: Avoid zero delay when receiving odd mixture of IGMP queries

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

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

From: Ben Hutchings <ben@...adent.org.uk>

commit a8c1f65c79cbbb2f7da782d4c9d15639a9b94b27 upstream.

Commit 5b7c84066733c5dfb0e4016d939757b38de189e4 ('ipv4: correct IGMP
behavior on v3 query during v2-compatibility mode') added yet another
case for query parsing, which can result in max_delay = 0.  Substitute
a value of 1, as in the usual v3 case.

Reported-by: Simon McVittie <smcv@...ian.org>
References: http://bugs.debian.org/654876
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: David S. Miller <davem@...emloft.net>

---
 net/ipv4/igmp.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -875,6 +875,8 @@ static void igmp_heard_query(struct in_d
 		 * to be intended in a v3 query.
 		 */
 		max_delay = IGMPV3_MRC(ih3->code)*(HZ/IGMP_TIMER_SCALE);
+		if (!max_delay)
+			max_delay = 1;	/* can't mod w/ 0 */
 	} else { /* v3 */
 		if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)))
 			return;

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