[IPV6] mcast: Fix multiple issues in MLDv2 reports.

The below "jumbo" patch fixes the following problems in MLDv2.

1) Add necessary "ntohs" to recent "pskb_may_pull" check [breaks
        all nonzero source queries on little-endian (!)]

2) Add locking to source filter list [resend of prior patch]

3) fix "mld_marksources()" to
        a) send nothing when all queried sources are excluded
        b) send full exclude report when source queried sources are
                not excluded
        c) don't schedule a timer when there's nothing to report

NOTE: RFC 3810 specifies the source list should be saved and each
  source reported individually as an IS_IN. This is an obvious DOS
  path, requiring the host to store and then multicast as many sources
  as are queried (e.g., millions...). This alternative sends a full, 
  relevant report that's limited to number of sources present on the
  machine.

4) fix "add_grec()" to send empty-source records when it should
        The original check doesn't account for a non-empty source
        list with all sources inactive; the new code keeps that
        short-circuit case, and also generates the group header
        with an empty list if needed.

5) fix mca_crcount decrement to be after add_grec(), which needs
        its original value

These issues (other than item #1 ;-) ) were all found by Yan Zheng,
much thanks!

Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 111 insertions, 30 deletions

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index d8234f9bd4c4..eb8afe3499a9 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -83,6 +83,7 @@ struct ipv6_mc_socklist
         struct in6_addr         addr;
         int                     ifindex;
         struct ipv6_mc_socklist *next;
+        rwlock_t                sflock;
         unsigned int            sfmode;         /* MCAST_{INCLUDE,EXCLUDE} */
         struct ip6_sf_socklist  *sflist;
 };
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 057d8619ba13..f829a4ad3ccc 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -224,6 +224,7 @@ int ipv6_sock_mc_join(struct sock *sk, int ifindex, struct in6_addr *addr)
 
         mc_lst->ifindex = dev->ifindex;
         mc_lst->sfmode = MCAST_EXCLUDE;
+        mc_lst->sflock = RW_LOCK_UNLOCKED;
         mc_lst->sflist = NULL;
 
         /*
@@ -360,6 +361,7 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
         struct ip6_sf_socklist *psl;
         int i, j, rv;
         int leavegroup = 0;
+        int pmclocked = 0;
         int err;
 
         if (pgsr->gsr_group.ss_family != AF_INET6 ||
@@ -403,6 +405,9 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
                 pmc->sfmode = omode;
         }
 
+        write_lock_bh(&pmc->sflock);
+        pmclocked = 1;
+
         psl = pmc->sflist;
         if (!add) {
                 if (!psl)
@@ -475,6 +480,8 @@ int ip6_mc_source(int add, int omode, struct sock *sk,
         /* update the interface list */
         ip6_mc_add_src(idev, group, omode, 1, source, 1);
 done:
+        if (pmclocked)
+                write_unlock_bh(&pmc->sflock);
         read_unlock_bh(&ipv6_sk_mc_lock);
         read_unlock_bh(&idev->lock);
         in6_dev_put(idev);
@@ -510,6 +517,8 @@ int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf)
         dev = idev->dev;
 
         err = 0;
+        read_lock_bh(&ipv6_sk_mc_lock);
+
         if (gsf->gf_fmode == MCAST_INCLUDE && gsf->gf_numsrc == 0) {
                 leavegroup = 1;
                 goto done;
@@ -549,6 +558,8 @@ int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf)
                 newpsl = NULL;
                 (void) ip6_mc_add_src(idev, group, gsf->gf_fmode, 0, NULL, 0);
         }
+
+        write_lock_bh(&pmc->sflock);
         psl = pmc->sflist;
         if (psl) {
                 (void) ip6_mc_del_src(idev, group, pmc->sfmode,
@@ -558,8 +569,10 @@ int ip6_mc_msfilter(struct sock *sk, struct group_filter *gsf)
                 (void) ip6_mc_del_src(idev, group, pmc->sfmode, 0, NULL, 0);
         pmc->sflist = newpsl;
         pmc->sfmode = gsf->gf_fmode;
+        write_unlock_bh(&pmc->sflock);
         err = 0;
 done:
+        read_unlock_bh(&ipv6_sk_mc_lock);
         read_unlock_bh(&idev->lock);
         in6_dev_put(idev);
         dev_put(dev);
@@ -592,6 +605,11 @@ int ip6_mc_msfget(struct sock *sk, struct group_filter *gsf,
         dev = idev->dev;
 
         err = -EADDRNOTAVAIL;
+        /*
+         * changes to the ipv6_mc_list require the socket lock and
+         * a read lock on ip6_sk_mc_lock. We have the socket lock,
+         * so reading the list is safe.
+         */
 
         for (pmc=inet6->ipv6_mc_list; pmc; pmc=pmc->next) {
                 if (pmc->ifindex != gsf->gf_interface)
@@ -614,6 +632,10 @@ int ip6_mc_msfget(struct sock *sk, struct group_filter *gsf,
             copy_to_user(optval, gsf, GROUP_FILTER_SIZE(0))) {
                 return -EFAULT;
         }
+        /* changes to psl require the socket lock, a read lock on
+         * on ipv6_sk_mc_lock and a write lock on pmc->sflock. We
+         * have the socket lock, so reading here is safe.
+         */
         for (i=0; i<copycount; i++) {
                 struct sockaddr_in6 *psin6;
                 struct sockaddr_storage ss;
@@ -650,6 +672,7 @@ int inet6_mc_check(struct sock *sk, struct in6_addr *mc_addr,
                 read_unlock(&ipv6_sk_mc_lock);
                 return 1;
         }
+        read_lock(&mc->sflock);
         psl = mc->sflist;
         if (!psl) {
                 rv = mc->sfmode == MCAST_EXCLUDE;
@@ -665,6 +688,7 @@ int inet6_mc_check(struct sock *sk, struct in6_addr *mc_addr,
                 if (mc->sfmode == MCAST_EXCLUDE && i < psl->sl_count)
                         rv = 0;
         }
+        read_unlock(&mc->sflock);
         read_unlock(&ipv6_sk_mc_lock);
 
         return rv;
@@ -1068,7 +1092,8 @@ static void igmp6_group_queried(struct ifmcaddr6 *ma, unsigned long resptime)
         ma->mca_flags |= MAF_TIMER_RUNNING;
 }
 
-static void mld_marksources(struct ifmcaddr6 *pmc, int nsrcs,
+/* mark EXCLUDE-mode sources */
+static int mld_xmarksources(struct ifmcaddr6 *pmc, int nsrcs,
         struct in6_addr *srcs)
 {
         struct ip6_sf_list *psf;
@@ -1078,13 +1103,53 @@ static void mld_marksources(struct ifmcaddr6 *pmc, int nsrcs,
         for (psf=pmc->mca_sources; psf; psf=psf->sf_next) {
                 if (scount == nsrcs)
                         break;
-                for (i=0; i<nsrcs; i++)
+                for (i=0; i<nsrcs; i++) {
+                        /* skip inactive filters */
+                        if (pmc->mca_sfcount[MCAST_INCLUDE] ||
+                            pmc->mca_sfcount[MCAST_EXCLUDE] !=
+                            psf->sf_count[MCAST_EXCLUDE])
+                                continue;
+                        if (ipv6_addr_equal(&srcs[i], &psf->sf_addr)) {
+                                scount++;
+                                break;
+                        }
+                }
+        }
+        pmc->mca_flags &= ~MAF_GSQUERY;
+        if (scount == nsrcs)    /* all sources excluded */
+                return 0;
+        return 1;
+}
+
+static int mld_marksources(struct ifmcaddr6 *pmc, int nsrcs,
+        struct in6_addr *srcs)
+{
+        struct ip6_sf_list *psf;
+        int i, scount;
+
+        if (pmc->mca_sfmode == MCAST_EXCLUDE)
+                return mld_xmarksources(pmc, nsrcs, srcs);
+
+        /* mark INCLUDE-mode sources */
+
+        scount = 0;
+        for (psf=pmc->mca_sources; psf; psf=psf->sf_next) {
+                if (scount == nsrcs)
+                        break;
+                for (i=0; i<nsrcs; i++) {
                         if (ipv6_addr_equal(&srcs[i], &psf->sf_addr)) {
                                 psf->sf_gsresp = 1;
                                 scount++;
                                 break;
                         }
+                }
+        }
+        if (!scount) {
+                pmc->mca_flags &= ~MAF_GSQUERY;
+                return 0;
         }
+        pmc->mca_flags |= MAF_GSQUERY;
+        return 1;
 }
 
 int igmp6_event_query(struct sk_buff *skb)
@@ -1167,7 +1232,7 @@ int igmp6_event_query(struct sk_buff *skb)
                 /* mark sources to include, if group & source-specific */
                 if (mlh2->nsrcs != 0) {
                         if (!pskb_may_pull(skb, srcs_offset + 
-                                mlh2->nsrcs * sizeof(struct in6_addr))) {
+                            ntohs(mlh2->nsrcs) * sizeof(struct in6_addr))) {
                                 in6_dev_put(idev);
                                 return -EINVAL;
                         }
@@ -1203,10 +1268,9 @@ int igmp6_event_query(struct sk_buff *skb)
                                 else
                                         ma->mca_flags &= ~MAF_GSQUERY;
                         }
-                        if (ma->mca_flags & MAF_GSQUERY)
-                                mld_marksources(ma, ntohs(mlh2->nsrcs),
-                                        mlh2->srcs);
-                        igmp6_group_queried(ma, max_delay);
+                        if (!(ma->mca_flags & MAF_GSQUERY) ||
+                           mld_marksources(ma, ntohs(mlh2->nsrcs), mlh2->srcs))
+                                igmp6_group_queried(ma, max_delay);
                         spin_unlock_bh(&ma->mca_lock);
                         if (group_type != IPV6_ADDR_ANY)
                                 break;
@@ -1281,7 +1345,18 @@ static int is_in(struct ifmcaddr6 *pmc, struct ip6_sf_list *psf, int type,
         case MLD2_MODE_IS_EXCLUDE:
                 if (gdeleted || sdeleted)
                         return 0;
-                return !((pmc->mca_flags & MAF_GSQUERY) && !psf->sf_gsresp);
+                if (!((pmc->mca_flags & MAF_GSQUERY) && !psf->sf_gsresp)) {
+                        if (pmc->mca_sfmode == MCAST_INCLUDE)
+                                return 1;
+                        /* don't include if this source is excluded
+                         * in all filters
+                         */
+                        if (psf->sf_count[MCAST_INCLUDE])
+                                return 0;
+                        return pmc->mca_sfcount[MCAST_EXCLUDE] ==
+                                psf->sf_count[MCAST_EXCLUDE];
+                }
+                return 0;
         case MLD2_CHANGE_TO_INCLUDE:
                 if (gdeleted || sdeleted)
                         return 0;
@@ -1450,7 +1525,7 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
         struct mld2_report *pmr;
         struct mld2_grec *pgr = NULL;
         struct ip6_sf_list *psf, *psf_next, *psf_prev, **psf_list;
-        int scount, first, isquery, truncate;
+        int scount, stotal, first, isquery, truncate;
 
         if (pmc->mca_flags & MAF_NOREPORT)
                 return skb;
@@ -1460,25 +1535,13 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
         truncate = type == MLD2_MODE_IS_EXCLUDE ||
                     type == MLD2_CHANGE_TO_EXCLUDE;
 
+        stotal = scount = 0;
+
         psf_list = sdeleted ? &pmc->mca_tomb : &pmc->mca_sources;
 
-        if (!*psf_list) {
-                if (type == MLD2_ALLOW_NEW_SOURCES ||
-                    type == MLD2_BLOCK_OLD_SOURCES)
-                        return skb;
-                if (pmc->mca_crcount || isquery) {
-                        /* make sure we have room for group header and at
-                         * least one source.
-                         */
-                        if (skb && AVAILABLE(skb) < sizeof(struct mld2_grec)+
-                            sizeof(struct in6_addr)) {
-                                mld_sendpack(skb);
-                                skb = NULL; /* add_grhead will get a new one */
-                        }
-                        skb = add_grhead(skb, pmc, type, &pgr);
-                }
-                return skb;
-        }
+        if (!*psf_list)
+                goto empty_source;
+
         pmr = skb ? (struct mld2_report *)skb->h.raw : NULL;
 
         /* EX and TO_EX get a fresh packet, if needed */
@@ -1491,7 +1554,6 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
                 }
         }
         first = 1;
-        scount = 0;
         psf_prev = NULL;
         for (psf=*psf_list; psf; psf=psf_next) {
                 struct in6_addr *psrc;
@@ -1525,7 +1587,7 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
                 }
                 psrc = (struct in6_addr *)skb_put(skb, sizeof(*psrc));
                 *psrc = psf->sf_addr;
-                scount++;
+                scount++; stotal++;
                 if ((type == MLD2_ALLOW_NEW_SOURCES ||
                      type == MLD2_BLOCK_OLD_SOURCES) && psf->sf_crcount) {
                         psf->sf_crcount--;
@@ -1540,6 +1602,21 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc,
                 }
                 psf_prev = psf;
         }
+
+empty_source:
+        if (!stotal) {
+                if (type == MLD2_ALLOW_NEW_SOURCES ||
+                    type == MLD2_BLOCK_OLD_SOURCES)
+                        return skb;
+                if (pmc->mca_crcount || isquery) {
+                        /* make sure we have room for group header */
+                        if (skb && AVAILABLE(skb) < sizeof(struct mld2_grec)) {
+                                mld_sendpack(skb);
+                                skb = NULL; /* add_grhead will get a new one */
+                        }
+                        skb = add_grhead(skb, pmc, type, &pgr);
+                }
+        }
         if (pgr)
                 pgr->grec_nsrcs = htons(scount);
 
@@ -1621,11 +1698,11 @@ static void mld_send_cr(struct inet6_dev *idev)
                         skb = add_grec(skb, pmc, dtype, 1, 1);
                 }
                 if (pmc->mca_crcount) {
-                        pmc->mca_crcount--;
                         if (pmc->mca_sfmode == MCAST_EXCLUDE) {
                                 type = MLD2_CHANGE_TO_INCLUDE;
                                 skb = add_grec(skb, pmc, type, 1, 0);
                         }
+                        pmc->mca_crcount--;
                         if (pmc->mca_crcount == 0) {
                                 mld_clear_zeros(&pmc->mca_tomb);
                                 mld_clear_zeros(&pmc->mca_sources);
@@ -1659,12 +1736,12 @@ static void mld_send_cr(struct inet6_dev *idev)
 
                 /* filter mode changes */
                 if (pmc->mca_crcount) {
-                        pmc->mca_crcount--;
                         if (pmc->mca_sfmode == MCAST_EXCLUDE)
                                 type = MLD2_CHANGE_TO_EXCLUDE;
                         else
                                 type = MLD2_CHANGE_TO_INCLUDE;
                         skb = add_grec(skb, pmc, type, 0, 0);
+                        pmc->mca_crcount--;
                 }
                 spin_unlock_bh(&pmc->mca_lock);
         }
@@ -2023,6 +2100,9 @@ static int ip6_mc_leave_src(struct sock *sk, struct ipv6_mc_socklist *iml,
 {
         int err;
 
+        /* callers have the socket lock and a write lock on ipv6_sk_mc_lock,
+         * so no other readers or writers of iml or its sflist
+         */
         if (iml->sflist == 0) {
                 /* any-source empty exclude case */
                 return ip6_mc_del_src(idev, &iml->addr, iml->sfmode, 0, NULL, 0);