igmp: Avoid zero delay when receiving odd mixture of IGMP queries

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@debian.org>
References: http://bugs.debian.org/654876
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index b2ca095..c3cc64c 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -875,6 +875,8 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
                 * to be intended in a v3 query.
                 */
                max_delay = IGMPV3_MRC(ih3->code)*(HZ/IGMP_TIMER_SCALE);
                 * 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;
        } else { /* v3 */
                if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)))
                        return;