igmp: fix ip_mc_sf_allow race [v5]

Almost all igmp functions accessing inet->mc_list are protected by
rtnl_lock(), but there is one exception which is ip_mc_sf_allow(),
so there is a chance of either ip_mc_drop_socket or ip_mc_leave_group
remove an entry while ip_mc_sf_allow is running causing a crash.

Signed-off-by: Flavio Leitner <fleitner@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/igmp.h b/include/linux/igmp.h
index 724c27e5d17355c0300294e30dbc52f6a19cc2dd..93fc2449af10e8dded6cbed23b4d979e4b5d10ef 100644 (file)
--- a/include/linux/igmp.h
+++ b/include/linux/igmp.h
@@ -153,6 +153,7 @@ extern int sysctl_igmp_max_msf;
 struct ip_sf_socklist {
        unsigned int            sl_max;
        unsigned int            sl_count;
+       struct rcu_head         rcu;
        __be32                  sl_addr[0];
 };
 
@@ -170,6 +171,7 @@ struct ip_mc_socklist {
        struct ip_mreqn         multi;
        unsigned int            sfmode;         /* MCAST_{INCLUDE,EXCLUDE} */
        struct ip_sf_socklist   *sflist;
+       struct rcu_head         rcu;
 };
 
 struct ip_sf_list {

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 8f5468393f014b48bfa2b9c9f801113779f488c4..d28363998743a0bf72188695ef1f6db6fa580bdb 100644 (file)
--- a/net/ipv4/igmp.c
+++ b/net/ipv4/igmp.c
@@ -1799,7 +1799,7 @@ int ip_mc_join_group(struct sock *sk , struct ip_mreqn *imr)
        iml->next = inet->mc_list;
        iml->sflist = NULL;
        iml->sfmode = MCAST_EXCLUDE;
-       inet->mc_list = iml;
+       rcu_assign_pointer(inet->mc_list, iml);
        ip_mc_inc_group(in_dev, addr);
        err = 0;
 done:
@@ -1807,24 +1807,46 @@ done:
        return err;
 }
 
+static void ip_sf_socklist_reclaim(struct rcu_head *rp)
+{
+       struct ip_sf_socklist *psf;
+
+       psf = container_of(rp, struct ip_sf_socklist, rcu);
+       /* sk_omem_alloc should have been decreased by the caller*/
+       kfree(psf);
+}
+
 static int ip_mc_leave_src(struct sock *sk, struct ip_mc_socklist *iml,
                           struct in_device *in_dev)
 {
+       struct ip_sf_socklist *psf = iml->sflist;
        int err;
 
-       if (iml->sflist == NULL) {
+       if (psf == NULL) {
                /* any-source empty exclude case */
                return ip_mc_del_src(in_dev, &iml->multi.imr_multiaddr.s_addr,
                        iml->sfmode, 0, NULL, 0);
        }
        err = ip_mc_del_src(in_dev, &iml->multi.imr_multiaddr.s_addr,
-                       iml->sfmode, iml->sflist->sl_count,
-                       iml->sflist->sl_addr, 0);
-       sock_kfree_s(sk, iml->sflist, IP_SFLSIZE(iml->sflist->sl_max));
-       iml->sflist = NULL;
+                       iml->sfmode, psf->sl_count, psf->sl_addr, 0);
+       rcu_assign_pointer(iml->sflist, NULL);
+       /* decrease mem now to avoid the memleak warning */
+       atomic_sub(IP_SFLSIZE(psf->sl_max), &sk->sk_omem_alloc);
+       call_rcu(&psf->rcu, ip_sf_socklist_reclaim);
        return err;
 }
 
+
+static void ip_mc_socklist_reclaim(struct rcu_head *rp)
+{
+       struct ip_mc_socklist *iml;
+
+       iml = container_of(rp, struct ip_mc_socklist, rcu);
+       /* sk_omem_alloc should have been decreased by the caller*/
+       kfree(iml);
+}
+
+
 /*
  *     Ask a socket to leave a group.
  */
@@ -1854,12 +1876,14 @@ int ip_mc_leave_group(struct sock *sk, struct ip_mreqn *imr)
 
                (void) ip_mc_leave_src(sk, iml, in_dev);
 
-               *imlp = iml->next;
+               rcu_assign_pointer(*imlp, iml->next);
 
                if (in_dev)
                        ip_mc_dec_group(in_dev, group);
                rtnl_unlock();
-               sock_kfree_s(sk, iml, sizeof(*iml));
+               /* decrease mem now to avoid the memleak warning */
+               atomic_sub(sizeof(*iml), &sk->sk_omem_alloc);
+               call_rcu(&iml->rcu, ip_mc_socklist_reclaim);
                return 0;
        }
        if (!in_dev)
@@ -1974,9 +1998,12 @@ int ip_mc_source(int add, int omode, struct sock *sk, struct
                if (psl) {
                        for (i=0; i<psl->sl_count; i++)
                                newpsl->sl_addr[i] = psl->sl_addr[i];
-                       sock_kfree_s(sk, psl, IP_SFLSIZE(psl->sl_max));
+                       /* decrease mem now to avoid the memleak warning */
+                       atomic_sub(IP_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc);
+                       call_rcu(&psl->rcu, ip_sf_socklist_reclaim);
                }
-               pmc->sflist = psl = newpsl;
+               rcu_assign_pointer(pmc->sflist, newpsl);
+               psl = newpsl;
        }
        rv = 1; /* > 0 for insert logic below if sl_count is 0 */
        for (i=0; i<psl->sl_count; i++) {
@@ -2072,11 +2099,13 @@ int ip_mc_msfilter(struct sock *sk, struct ip_msfilter *msf, int ifindex)
        if (psl) {
                (void) ip_mc_del_src(in_dev, &msf->imsf_multiaddr, pmc->sfmode,
                        psl->sl_count, psl->sl_addr, 0);
-               sock_kfree_s(sk, psl, IP_SFLSIZE(psl->sl_max));
+               /* decrease mem now to avoid the memleak warning */
+               atomic_sub(IP_SFLSIZE(psl->sl_max), &sk->sk_omem_alloc);
+               call_rcu(&psl->rcu, ip_sf_socklist_reclaim);
        } else
                (void) ip_mc_del_src(in_dev, &msf->imsf_multiaddr, pmc->sfmode,
                        0, NULL, 0);
-       pmc->sflist = newpsl;
+       rcu_assign_pointer(pmc->sflist, newpsl);
        pmc->sfmode = msf->imsf_fmode;
        err = 0;
 done:
@@ -2209,30 +2238,40 @@ int ip_mc_sf_allow(struct sock *sk, __be32 loc_addr, __be32 rmt_addr, int dif)
        struct ip_mc_socklist *pmc;
        struct ip_sf_socklist *psl;
        int i;
+       int ret;
 
+       ret = 1;
        if (!ipv4_is_multicast(loc_addr))
-               return 1;
+               goto out;
 
-       for (pmc=inet->mc_list; pmc; pmc=pmc->next) {
+       rcu_read_lock();
+       for (pmc=rcu_dereference(inet->mc_list); pmc; pmc=rcu_dereference(pmc->next)) {
                if (pmc->multi.imr_multiaddr.s_addr == loc_addr &&
                    pmc->multi.imr_ifindex == dif)
                        break;
        }
+       ret = inet->mc_all;
        if (!pmc)
-               return inet->mc_all;
+               goto unlock;
        psl = pmc->sflist;
+       ret = (pmc->sfmode == MCAST_EXCLUDE);
        if (!psl)
-               return pmc->sfmode == MCAST_EXCLUDE;
+               goto unlock;
 
        for (i=0; i<psl->sl_count; i++) {
                if (psl->sl_addr[i] == rmt_addr)
                        break;
        }
+       ret = 0;
        if (pmc->sfmode == MCAST_INCLUDE && i >= psl->sl_count)
-               return 0;
+               goto unlock;
        if (pmc->sfmode == MCAST_EXCLUDE && i < psl->sl_count)
-               return 0;
-       return 1;
+               goto unlock;
+       ret = 1;
+unlock:
+       rcu_read_unlock();
+out:
+       return ret;
 }
 
 /*
@@ -2251,7 +2290,7 @@ void ip_mc_drop_socket(struct sock *sk)
        rtnl_lock();
        while ((iml = inet->mc_list) != NULL) {
                struct in_device *in_dev;
-               inet->mc_list = iml->next;
+               rcu_assign_pointer(inet->mc_list, iml->next);
 
                in_dev = inetdev_by_index(net, iml->multi.imr_ifindex);
                (void) ip_mc_leave_src(sk, iml, in_dev);
@@ -2259,7 +2298,9 @@ void ip_mc_drop_socket(struct sock *sk)
                        ip_mc_dec_group(in_dev, iml->multi.imr_multiaddr.s_addr);
                        in_dev_put(in_dev);
                }
-               sock_kfree_s(sk, iml, sizeof(*iml));
+               /* decrease mem now to avoid the memleak warning */
+               atomic_sub(sizeof(*iml), &sk->sk_omem_alloc);
+               call_rcu(&iml->rcu, ip_mc_socklist_reclaim);
        }
        rtnl_unlock();
 }