1 files changed, 14 insertions, 7 deletions

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 6b3c558a4f23..a51360087b19 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -803,10 +803,17 @@ static void igmp_gq_timer_expire(struct timer_list *t)
 static void igmp_ifc_timer_expire(struct timer_list *t)
 {
 	struct in_device *in_dev = from_timer(in_dev, t, mr_ifc_timer);
+	u8 mr_ifc_count;
 
 	igmpv3_send_cr(in_dev);
-	if (in_dev->mr_ifc_count) {
-		in_dev->mr_ifc_count--;
+restart:
+	mr_ifc_count = READ_ONCE(in_dev->mr_ifc_count);
+
+	if (mr_ifc_count) {
+		if (cmpxchg(&in_dev->mr_ifc_count,
+			    mr_ifc_count,
+			    mr_ifc_count - 1) != mr_ifc_count)
+			goto restart;
 		igmp_ifc_start_timer(in_dev,
 				     unsolicited_report_interval(in_dev));
 	}
@@ -818,7 +825,7 @@ static void igmp_ifc_event(struct in_device *in_dev)
 	struct net *net = dev_net(in_dev->dev);
 	if (IGMP_V1_SEEN(in_dev) || IGMP_V2_SEEN(in_dev))
 		return;
-	in_dev->mr_ifc_count = in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv;
+	WRITE_ONCE(in_dev->mr_ifc_count, in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv);
 	igmp_ifc_start_timer(in_dev, 1);
 }
 
@@ -957,7 +964,7 @@ static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
 				in_dev->mr_qri;
 		}
 		/* cancel the interface change timer */
-		in_dev->mr_ifc_count = 0;
+		WRITE_ONCE(in_dev->mr_ifc_count, 0);
 		if (del_timer(&in_dev->mr_ifc_timer))
 			__in_dev_put(in_dev);
 		/* clear deleted report items */
@@ -1724,7 +1731,7 @@ void ip_mc_down(struct in_device *in_dev)
 		igmp_group_dropped(pmc);
 
 #ifdef CONFIG_IP_MULTICAST
-	in_dev->mr_ifc_count = 0;
+	WRITE_ONCE(in_dev->mr_ifc_count, 0);
 	if (del_timer(&in_dev->mr_ifc_timer))
 		__in_dev_put(in_dev);
 	in_dev->mr_gq_running = 0;
@@ -1941,7 +1948,7 @@ static int ip_mc_del_src(struct in_device *in_dev, __be32 *pmca, int sfmode,
 		pmc->sfmode = MCAST_INCLUDE;
 #ifdef CONFIG_IP_MULTICAST
 		pmc->crcount = in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv;
-		in_dev->mr_ifc_count = pmc->crcount;
+		WRITE_ONCE(in_dev->mr_ifc_count, pmc->crcount);
 		for (psf = pmc->sources; psf; psf = psf->sf_next)
 			psf->sf_crcount = 0;
 		igmp_ifc_event(pmc->interface);
@@ -2120,7 +2127,7 @@ static int ip_mc_add_src(struct in_device *in_dev, __be32 *pmca, int sfmode,
 		/* else no filters; keep old mode for reports */
 
 		pmc->crcount = in_dev->mr_qrv ?: net->ipv4.sysctl_igmp_qrv;
-		in_dev->mr_ifc_count = pmc->crcount;
+		WRITE_ONCE(in_dev->mr_ifc_count, pmc->crcount);
 		for (psf = pmc->sources; psf; psf = psf->sf_next)
 			psf->sf_crcount = 0;
 		igmp_ifc_event(in_dev);