igmp: avoid drop_monitor false positives

igmp should call consume_skb() for all correctly processed packets,
to avoid false dropwatch/drop_monitor false positives.

Reported-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 0b5580c..3479b98 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -815,14 +815,15 @@ static int igmp_marksources(struct ip_mc_list *pmc, int nsrcs, __be32 *srcs)
        return 1;
 }
 
-static void igmp_heard_report(struct in_device *in_dev, __be32 group)
+/* return true if packet was dropped */
+static bool igmp_heard_report(struct in_device *in_dev, __be32 group)
 {
        struct ip_mc_list *im;
 
        /* Timers are only set for non-local groups */
 
        if (group == IGMP_ALL_HOSTS)
-               return;
+               return false;
 
        rcu_read_lock();
        for_each_pmc_rcu(in_dev, im) {
@@ -832,9 +833,11 @@ static void igmp_heard_report(struct in_device *in_dev, __be32 group)
                }
        }
        rcu_read_unlock();
+       return false;
 }
 
-static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
+/* return true if packet was dropped */
+static bool igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
        int len)
 {
        struct igmphdr          *ih = igmp_hdr(skb);
@@ -866,7 +869,7 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
                /* clear deleted report items */
                igmpv3_clear_delrec(in_dev);
        } else if (len < 12) {
-               return; /* ignore bogus packet; freed by caller */
+               return true;    /* ignore bogus packet; freed by caller */
        } else if (IGMP_V1_SEEN(in_dev)) {
                /* This is a v3 query with v1 queriers present */
                max_delay = IGMP_Query_Response_Interval;
@@ -883,13 +886,13 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
                        max_delay = 1;  /* can't mod w/ 0 */
        } else { /* v3 */
                if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)))
-                       return;
+                       return true;
 
                ih3 = igmpv3_query_hdr(skb);
                if (ih3->nsrcs) {
                        if (!pskb_may_pull(skb, sizeof(struct igmpv3_query)
                                           + ntohs(ih3->nsrcs)*sizeof(__be32)))
-                               return;
+                               return true;
                        ih3 = igmpv3_query_hdr(skb);
                }
 
@@ -901,9 +904,9 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
                        in_dev->mr_qrv = ih3->qrv;
                if (!group) { /* general query */
                        if (ih3->nsrcs)
-                               return; /* no sources allowed */
+                               return false;   /* no sources allowed */
                        igmp_gq_start_timer(in_dev);
-                       return;
+                       return false;
                }
                /* mark sources to include, if group & source-specific */
                mark = ih3->nsrcs != 0;
@@ -939,6 +942,7 @@ static void igmp_heard_query(struct in_device *in_dev, struct sk_buff *skb,
                        igmp_mod_timer(im, max_delay);
        }
        rcu_read_unlock();
+       return false;
 }
 
 /* called in rcu_read_lock() section */
@@ -948,6 +952,7 @@ int igmp_rcv(struct sk_buff *skb)
        struct igmphdr *ih;
        struct in_device *in_dev = __in_dev_get_rcu(skb->dev);
        int len = skb->len;
+       bool dropped = true;
 
        if (in_dev == NULL)
                goto drop;
@@ -969,7 +974,7 @@ int igmp_rcv(struct sk_buff *skb)
        ih = igmp_hdr(skb);
        switch (ih->type) {
        case IGMP_HOST_MEMBERSHIP_QUERY:
-               igmp_heard_query(in_dev, skb, len);
+               dropped = igmp_heard_query(in_dev, skb, len);
                break;
        case IGMP_HOST_MEMBERSHIP_REPORT:
        case IGMPV2_HOST_MEMBERSHIP_REPORT:
@@ -979,7 +984,7 @@ int igmp_rcv(struct sk_buff *skb)
                /* don't rely on MC router hearing unicast reports */
                if (skb->pkt_type == PACKET_MULTICAST ||
                    skb->pkt_type == PACKET_BROADCAST)
-                       igmp_heard_report(in_dev, ih->group);
+                       dropped = igmp_heard_report(in_dev, ih->group);
                break;
        case IGMP_PIM:
 #ifdef CONFIG_IP_PIMSM_V1
@@ -997,7 +1002,10 @@ int igmp_rcv(struct sk_buff *skb)
        }
 
 drop:
-       kfree_skb(skb);
+       if (dropped)
+               kfree_skb(skb);
+       else
+               consume_skb(skb);
        return 0;
 }