[PATCH net] igmp: Avoid zero delay when receiving odd mixture of IGMP queries

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 <redacted>
References: http://bugs.debian.org/654876
Signed-off-by: Ben Hutchings <redacted>
---
 net/ipv4/igmp.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index d577199..e0d42db 100644
--- 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);
+		if (!max_delay)
+			max_delay = 1;	/* can't mod w/ 0 */
 	} else { /* v3 */
 		if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)))
 			return;

-- 
1.7.8.2

From: Ben Hutchings <redacted>
Date: Mon, 9 Jan 2012 22:04:28 +0000

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 <redacted>
References: http://bugs.debian.org/654876
Signed-off-by: Ben Hutchings <redacted>

Applied and queued up for -stable, thanks Ben.

On Mon, 2012-01-09 at 22:04 +0000, Ben Hutchings wrote:

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.

This has been assigned CVE-2012-0207.

Ben.

-- 
Ben Hutchings
Life is what happens to you while you're busy making other plans.
                                                               - John Lennon