[SCTP]: Add RCU synchronization around sctp_localaddr_list

sctp_localaddr_list is modified dynamically via NETDEV_UP
and NETDEV_DOWN events, but there is not synchronization
between writer (even handler) and readers.  As a result,
the readers can access an entry that has been freed and
crash the sytem.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Sridhar Samdurala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index d529045..c9cc00c 100644 (file)
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -123,6 +123,7 @@
  * sctp/protocol.c
  */
 extern struct sock *sctp_get_ctl_sock(void);
+extern void sctp_local_addr_free(struct rcu_head *head);
 extern int sctp_copy_local_addr_list(struct sctp_bind_addr *,
                                     sctp_scope_t, gfp_t gfp,
                                     int flags);

diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index c0d5848..a89e361 100644 (file)
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -207,6 +207,9 @@ extern struct sctp_globals {
         * It is a list of sctp_sockaddr_entry.
         */
        struct list_head local_addr_list;
+
+       /* Lock that protects the local_addr_list writers */
+       spinlock_t addr_list_lock;
        
        /* Flag to indicate if addip is enabled. */
        int addip_enable;
@@ -242,6 +245,7 @@ extern struct sctp_globals {
 #define sctp_port_alloc_lock           (sctp_globals.port_alloc_lock)
 #define sctp_port_hashtable            (sctp_globals.port_hashtable)
 #define sctp_local_addr_list           (sctp_globals.local_addr_list)
+#define sctp_local_addr_lock           (sctp_globals.addr_list_lock)
 #define sctp_addip_enable              (sctp_globals.addip_enable)
 #define sctp_prsctp_enable             (sctp_globals.prsctp_enable)
 
@@ -737,8 +741,10 @@ const union sctp_addr *sctp_source(const struct sctp_chunk *chunk);
 /* This is a structure for holding either an IPv6 or an IPv4 address.  */
 struct sctp_sockaddr_entry {
        struct list_head list;
+       struct rcu_head rcu;
        union sctp_addr a;
        __u8 use_as_src;
+       __u8 valid;
 };
 
 typedef struct sctp_chunk *(sctp_packet_phandler_t)(struct sctp_association *);

diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
index fdb287a..7fc369f 100644 (file)
--- a/net/sctp/bind_addr.c
+++ b/net/sctp/bind_addr.c
@@ -163,8 +163,10 @@ int sctp_add_bind_addr(struct sctp_bind_addr *bp, union sctp_addr *new,
                addr->a.v4.sin_port = htons(bp->port);
 
        addr->use_as_src = use_as_src;
+       addr->valid = 1;
 
        INIT_LIST_HEAD(&addr->list);
+       INIT_RCU_HEAD(&addr->rcu);
        list_add_tail(&addr->list, &bp->address_list);
        SCTP_DBG_OBJCNT_INC(addr);
 

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index f8aa23d..e12fa0a 100644 (file)
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -77,13 +77,18 @@
 
 #include <asm/uaccess.h>
 
-/* Event handler for inet6 address addition/deletion events.  */
+/* Event handler for inet6 address addition/deletion events.
+ * The sctp_local_addr_list needs to be protocted by a spin lock since
+ * multiple notifiers (say IPv4 and IPv6) may be running at the same
+ * time and thus corrupt the list.
+ * The reader side is protected with RCU.
+ */
 static int sctp_inet6addr_event(struct notifier_block *this, unsigned long ev,
                                void *ptr)
 {
        struct inet6_ifaddr *ifa = (struct inet6_ifaddr *)ptr;
-       struct sctp_sockaddr_entry *addr;
-       struct list_head *pos, *temp;
+       struct sctp_sockaddr_entry *addr = NULL;
+       struct sctp_sockaddr_entry *temp;
 
        switch (ev) {
        case NETDEV_UP:
@@ -94,19 +99,26 @@ static int sctp_inet6addr_event(struct notifier_block *this, unsigned long ev,
                        memcpy(&addr->a.v6.sin6_addr, &ifa->addr,
                                 sizeof(struct in6_addr));
                        addr->a.v6.sin6_scope_id = ifa->idev->dev->ifindex;
-                       list_add_tail(&addr->list, &sctp_local_addr_list);
+                       addr->valid = 1;
+                       spin_lock_bh(&sctp_local_addr_lock);
+                       list_add_tail_rcu(&addr->list, &sctp_local_addr_list);
+                       spin_unlock_bh(&sctp_local_addr_lock);
                }
                break;
        case NETDEV_DOWN:
-               list_for_each_safe(pos, temp, &sctp_local_addr_list) {
-                       addr = list_entry(pos, struct sctp_sockaddr_entry, list);
-                       if (ipv6_addr_equal(&addr->a.v6.sin6_addr, &ifa->addr)) {
-                               list_del(pos);
-                               kfree(addr);
+               spin_lock_bh(&sctp_local_addr_lock);
+               list_for_each_entry_safe(addr, temp,
+                                       &sctp_local_addr_list, list) {
+                       if (ipv6_addr_equal(&addr->a.v6.sin6_addr,
+                                            &ifa->addr)) {
+                               addr->valid = 0;
+                               list_del_rcu(&addr->list);
                                break;
                        }
                }
-
+               spin_unlock_bh(&sctp_local_addr_lock);
+               if (addr && !addr->valid)
+                       call_rcu(&addr->rcu, sctp_local_addr_free);
                break;
        }
 
@@ -367,7 +379,9 @@ static void sctp_v6_copy_addrlist(struct list_head *addrlist,
                        addr->a.v6.sin6_port = 0;
                        addr->a.v6.sin6_addr = ifp->addr;
                        addr->a.v6.sin6_scope_id = dev->ifindex;
+                       addr->valid = 1;
                        INIT_LIST_HEAD(&addr->list);
+                       INIT_RCU_HEAD(&addr->rcu);
                        list_add_tail(&addr->list, addrlist);
                }
        }

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index e98579b..7ee120e 100644 (file)
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -153,6 +153,9 @@ static void sctp_v4_copy_addrlist(struct list_head *addrlist,
                        addr->a.v4.sin_family = AF_INET;
                        addr->a.v4.sin_port = 0;
                        addr->a.v4.sin_addr.s_addr = ifa->ifa_local;
+                       addr->valid = 1;
+                       INIT_LIST_HEAD(&addr->list);
+                       INIT_RCU_HEAD(&addr->rcu);
                        list_add_tail(&addr->list, addrlist);
                }
        }
@@ -192,16 +195,24 @@ static void sctp_free_local_addr_list(void)
        }
 }
 
+void sctp_local_addr_free(struct rcu_head *head)
+{
+       struct sctp_sockaddr_entry *e = container_of(head,
+                               struct sctp_sockaddr_entry, rcu);
+       kfree(e);
+}
+
 /* Copy the local addresses which are valid for 'scope' into 'bp'.  */
 int sctp_copy_local_addr_list(struct sctp_bind_addr *bp, sctp_scope_t scope,
                              gfp_t gfp, int copy_flags)
 {
        struct sctp_sockaddr_entry *addr;
        int error = 0;
-       struct list_head *pos, *temp;
 
-       list_for_each_safe(pos, temp, &sctp_local_addr_list) {
-               addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+       rcu_read_lock();
+       list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
+               if (!addr->valid)
+                       continue;
                if (sctp_in_scope(&addr->a, scope)) {
                        /* Now that the address is in scope, check to see if
                         * the address type is really supported by the local
@@ -221,6 +232,7 @@ int sctp_copy_local_addr_list(struct sctp_bind_addr *bp, sctp_scope_t scope,
        }
 
 end_copy:
+       rcu_read_unlock();
        return error;
 }
 
@@ -600,13 +612,18 @@ static void sctp_v4_seq_dump_addr(struct seq_file *seq, union sctp_addr *addr)
        seq_printf(seq, "%d.%d.%d.%d ", NIPQUAD(addr->v4.sin_addr));
 }
 
-/* Event handler for inet address addition/deletion events.  */
+/* Event handler for inet address addition/deletion events.
+ * The sctp_local_addr_list needs to be protocted by a spin lock since
+ * multiple notifiers (say IPv4 and IPv6) may be running at the same
+ * time and thus corrupt the list.
+ * The reader side is protected with RCU.
+ */
 static int sctp_inetaddr_event(struct notifier_block *this, unsigned long ev,
                               void *ptr)
 {
        struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
-       struct sctp_sockaddr_entry *addr;
-       struct list_head *pos, *temp;
+       struct sctp_sockaddr_entry *addr = NULL;
+       struct sctp_sockaddr_entry *temp;
 
        switch (ev) {
        case NETDEV_UP:
@@ -615,19 +632,25 @@ static int sctp_inetaddr_event(struct notifier_block *this, unsigned long ev,
                        addr->a.v4.sin_family = AF_INET;
                        addr->a.v4.sin_port = 0;
                        addr->a.v4.sin_addr.s_addr = ifa->ifa_local;
-                       list_add_tail(&addr->list, &sctp_local_addr_list);
+                       addr->valid = 1;
+                       spin_lock_bh(&sctp_local_addr_lock);
+                       list_add_tail_rcu(&addr->list, &sctp_local_addr_list);
+                       spin_unlock_bh(&sctp_local_addr_lock);
                }
                break;
        case NETDEV_DOWN:
-               list_for_each_safe(pos, temp, &sctp_local_addr_list) {
-                       addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+               spin_lock_bh(&sctp_local_addr_lock);
+               list_for_each_entry_safe(addr, temp,
+                                       &sctp_local_addr_list, list) {
                        if (addr->a.v4.sin_addr.s_addr == ifa->ifa_local) {
-                               list_del(pos);
-                               kfree(addr);
+                               addr->valid = 0;
+                               list_del_rcu(&addr->list);
                                break;
                        }
                }
-
+               spin_unlock_bh(&sctp_local_addr_lock);
+               if (addr && !addr->valid)
+                       call_rcu(&addr->rcu, sctp_local_addr_free);
                break;
        }
 
@@ -1160,6 +1183,7 @@ SCTP_STATIC __init int sctp_init(void)
 
        /* Initialize the local address list. */
        INIT_LIST_HEAD(&sctp_local_addr_list);
+       spin_lock_init(&sctp_local_addr_lock);
        sctp_get_local_addr_list();
 
        /* Register notifier for inet address additions/deletions. */
@@ -1227,6 +1251,9 @@ SCTP_STATIC __exit void sctp_exit(void)
        sctp_v6_del_protocol();
        inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
 
+       /* Unregister notifier for inet address additions/deletions. */
+       unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
+
        /* Free the local address list.  */
        sctp_free_local_addr_list();
 
@@ -1240,9 +1267,6 @@ SCTP_STATIC __exit void sctp_exit(void)
        inet_unregister_protosw(&sctp_stream_protosw);
        inet_unregister_protosw(&sctp_seqpacket_protosw);
 
-       /* Unregister notifier for inet address additions/deletions. */
-       unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
-
        sctp_sysctl_unregister();
        list_del(&sctp_ipv4_specific.list);
 

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 3335460..a3acf78 100644 (file)
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4057,9 +4057,9 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
                                               int __user *optlen)
 {
        sctp_assoc_t id;
+       struct list_head *pos;
        struct sctp_bind_addr *bp;
        struct sctp_association *asoc;
-       struct list_head *pos, *temp;
        struct sctp_sockaddr_entry *addr;
        rwlock_t *addr_lock;
        int cnt = 0;
@@ -4096,15 +4096,19 @@ static int sctp_getsockopt_local_addrs_num_old(struct sock *sk, int len,
                addr = list_entry(bp->address_list.next,
                                  struct sctp_sockaddr_entry, list);
                if (sctp_is_any(&addr->a)) {
-                       list_for_each_safe(pos, temp, &sctp_local_addr_list) {
-                               addr = list_entry(pos,
-                                                 struct sctp_sockaddr_entry,
-                                                 list);
+                       rcu_read_lock();
+                       list_for_each_entry_rcu(addr,
+                                               &sctp_local_addr_list, list) {
+                               if (!addr->valid)
+                                       continue;
+
                                if ((PF_INET == sk->sk_family) &&
                                    (AF_INET6 == addr->a.sa.sa_family))
                                        continue;
+
                                cnt++;
                        }
+                       rcu_read_unlock();
                } else {
                        cnt = 1;
                }
@@ -4127,14 +4131,16 @@ static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
                                        int max_addrs, void *to,
                                        int *bytes_copied)
 {
-       struct list_head *pos, *next;
        struct sctp_sockaddr_entry *addr;
        union sctp_addr temp;
        int cnt = 0;
        int addrlen;
 
-       list_for_each_safe(pos, next, &sctp_local_addr_list) {
-               addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+       rcu_read_lock();
+       list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
+               if (!addr->valid)
+                       continue;
+
                if ((PF_INET == sk->sk_family) &&
                    (AF_INET6 == addr->a.sa.sa_family))
                        continue;
@@ -4149,6 +4155,7 @@ static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
                cnt ++;
                if (cnt >= max_addrs) break;
        }
+       rcu_read_unlock();
 
        return cnt;
 }
@@ -4156,14 +4163,16 @@ static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
 static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
                            size_t space_left, int *bytes_copied)
 {
-       struct list_head *pos, *next;
        struct sctp_sockaddr_entry *addr;
        union sctp_addr temp;
        int cnt = 0;
        int addrlen;
 
-       list_for_each_safe(pos, next, &sctp_local_addr_list) {
-               addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+       rcu_read_lock();
+       list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
+               if (!addr->valid)
+                       continue;
+
                if ((PF_INET == sk->sk_family) &&
                    (AF_INET6 == addr->a.sa.sa_family))
                        continue;
@@ -4171,8 +4180,10 @@ static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
                sctp_get_pf_specific(sk->sk_family)->addr_v4map(sctp_sk(sk),
                                                                &temp);
                addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
-               if (space_left < addrlen)
-                       return -ENOMEM;
+               if (space_left < addrlen) {
+                       cnt =  -ENOMEM;
+                       break;
+               }
                memcpy(to, &temp, addrlen);
 
                to += addrlen;
@@ -4180,6 +4191,7 @@ static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
                space_left -= addrlen;
                *bytes_copied += addrlen;
        }
+       rcu_read_unlock();
 
        return cnt;
 }