diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 00576bae183d..0c321996c6eb 100644
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -2720,6 +2720,7 @@ int ip_check_mc_rcu(struct in_device *in_dev, __be32 mc_addr, __be32 src_addr, u
 		rv = 1;
 	} else if (im) {
 		if (src_addr) {
+			spin_lock_bh(&im->lock);
 			for (psf = im->sources; psf; psf = psf->sf_next) {
 				if (psf->sf_inaddr == src_addr)
 					break;
@@ -2730,6 +2731,7 @@ int ip_check_mc_rcu(struct in_device *in_dev, __be32 mc_addr, __be32 src_addr, u
 					im->sfcount[MCAST_EXCLUDE];
 			else
 				rv = im->sfcount[MCAST_EXCLUDE] != 0;
+			spin_unlock_bh(&im->lock);
 		} else
 			rv = 1; /* unspecified source; tentatively allow */
 	}