2 files changed, 89 insertions, 67 deletions

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 7523f4df2da6..1662f9cc869e 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -73,6 +73,8 @@ static struct sctp_association *__sctp_lookup_association(
                                         const union sctp_addr *peer,
                                         struct sctp_transport **pt);
 
+static void sctp_add_backlog(struct sock *sk, struct sk_buff *skb);
+
 
 /* Calculate the SCTP checksum of an SCTP packet.  */
 static inline int sctp_rcv_checksum(struct sk_buff *skb)
@@ -186,7 +188,6 @@ int sctp_rcv(struct sk_buff *skb)
          */
         if (sk->sk_bound_dev_if && (sk->sk_bound_dev_if != af->skb_iif(skb)))
         {
-                sock_put(sk);
                 if (asoc) {
                         sctp_association_put(asoc);
                         asoc = NULL;
@@ -197,7 +198,6 @@ int sctp_rcv(struct sk_buff *skb)
                 sk = sctp_get_ctl_sock();
                 ep = sctp_sk(sk)->ep;
                 sctp_endpoint_hold(ep);
-                sock_hold(sk);
                 rcvr = &ep->base;
         }
 
@@ -253,25 +253,18 @@ int sctp_rcv(struct sk_buff *skb)
          */
         sctp_bh_lock_sock(sk);
 
-        /* It is possible that the association could have moved to a different
-         * socket if it is peeled off. If so, update the sk.
-         */ 
-        if (sk != rcvr->sk) {
-                sctp_bh_lock_sock(rcvr->sk);
-                sctp_bh_unlock_sock(sk);
-                sk = rcvr->sk;
-        }
-
         if (sock_owned_by_user(sk))
-                sk_add_backlog(sk, skb);
+                sctp_add_backlog(sk, skb);
         else
-                sctp_backlog_rcv(sk, skb);
+                sctp_inq_push(&chunk->rcvr->inqueue, chunk);
 
-        /* Release the sock and the sock ref we took in the lookup calls.
-         * The asoc/ep ref will be released in sctp_backlog_rcv.
-         */
         sctp_bh_unlock_sock(sk);
-        sock_put(sk);
+
+        /* Release the asoc/ep ref we took in the lookup calls. */
+        if (asoc)
+                sctp_association_put(asoc);
+        else
+                sctp_endpoint_put(ep);
 
         return 0;
 
@@ -280,8 +273,7 @@ discard_it:
         return 0;
 
 discard_release:
-        /* Release any structures we may be holding. */
-        sock_put(sk);
+        /* Release the asoc/ep ref we took in the lookup calls. */
         if (asoc)
                 sctp_association_put(asoc);
         else
@@ -290,56 +282,87 @@ discard_release:
         goto discard_it;
 }
 
-/* Handle second half of inbound skb processing.  If the sock was busy,
- * we may have need to delay processing until later when the sock is
- * released (on the backlog).   If not busy, we call this routine
- * directly from the bottom half.
+/* Process the backlog queue of the socket.  Every skb on
+ * the backlog holds a ref on an association or endpoint.
+ * We hold this ref throughout the state machine to make
+ * sure that the structure we need is still around.
  */
 int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb)
 {
         struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
-        struct sctp_inq *inqueue = NULL;
+        struct sctp_inq *inqueue = &chunk->rcvr->inqueue;
         struct sctp_ep_common *rcvr = NULL;
+        int backloged = 0;
 
         rcvr = chunk->rcvr;
 
-        BUG_TRAP(rcvr->sk == sk);
-
-        if (rcvr->dead) {
-                sctp_chunk_free(chunk);
-        } else {
-                inqueue = &chunk->rcvr->inqueue;
-                sctp_inq_push(inqueue, chunk);
-        }
-
-        /* Release the asoc/ep ref we took in the lookup calls in sctp_rcv. */ 
-        if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
-                sctp_association_put(sctp_assoc(rcvr));
-        else
-                sctp_endpoint_put(sctp_ep(rcvr));
-  
+        /* If the rcvr is dead then the association or endpoint
+         * has been deleted and we can safely drop the chunk
+         * and refs that we are holding.
+         */
+        if (rcvr->dead) {
+                sctp_chunk_free(chunk);
+                goto done;
+        }
+
+        if (unlikely(rcvr->sk != sk)) {
+                /* In this case, the association moved from one socket to
+                 * another.  We are currently sitting on the backlog of the
+                 * old socket, so we need to move.
+                 * However, since we are here in the process context we
+                 * need to take make sure that the user doesn't own
+                 * the new socket when we process the packet.
+                 * If the new socket is user-owned, queue the chunk to the
+                 * backlog of the new socket without dropping any refs.
+                 * Otherwise, we can safely push the chunk on the inqueue.
+                 */
+
+                sk = rcvr->sk;
+                sctp_bh_lock_sock(sk);
+
+                if (sock_owned_by_user(sk)) {
+                        sk_add_backlog(sk, skb);
+                        backloged = 1;
+                } else
+                        sctp_inq_push(inqueue, chunk);
+
+                sctp_bh_unlock_sock(sk);
+
+                /* If the chunk was backloged again, don't drop refs */
+                if (backloged)
+                        return 0;
+        } else {
+                sctp_inq_push(inqueue, chunk);
+        }
+
+done:
+        /* Release the refs we took in sctp_add_backlog */
+        if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
+                sctp_association_put(sctp_assoc(rcvr));
+        else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
+                sctp_endpoint_put(sctp_ep(rcvr));
+        else
+                BUG();
+
         return 0;
 }
 
-void sctp_backlog_migrate(struct sctp_association *assoc, 
-                          struct sock *oldsk, struct sock *newsk)
+static void sctp_add_backlog(struct sock *sk, struct sk_buff *skb)
 {
-        struct sk_buff *skb;
-        struct sctp_chunk *chunk;
+        struct sctp_chunk *chunk = SCTP_INPUT_CB(skb)->chunk;
+        struct sctp_ep_common *rcvr = chunk->rcvr;
 
-        skb = oldsk->sk_backlog.head;
-        oldsk->sk_backlog.head = oldsk->sk_backlog.tail = NULL;
-        while (skb != NULL) {
-                struct sk_buff *next = skb->next;
-
-                chunk = SCTP_INPUT_CB(skb)->chunk;
-                skb->next = NULL;
-                if (&assoc->base == chunk->rcvr)
-                        sk_add_backlog(newsk, skb);
-                else
-                        sk_add_backlog(oldsk, skb);
-                skb = next;
-        }
+        /* Hold the assoc/ep while hanging on the backlog queue.
+         * This way, we know structures we need will not disappear from us
+         */
+        if (SCTP_EP_TYPE_ASSOCIATION == rcvr->type)
+                sctp_association_hold(sctp_assoc(rcvr));
+        else if (SCTP_EP_TYPE_SOCKET == rcvr->type)
+                sctp_endpoint_hold(sctp_ep(rcvr));
+        else
+                BUG();
+
+        sk_add_backlog(sk, skb);
 }
 
 /* Handle icmp frag needed error. */
@@ -453,7 +476,6 @@ struct sock *sctp_err_lookup(int family, struct sk_buff *skb,
         return sk;
 
 out:
-        sock_put(sk);
         if (asoc)
                 sctp_association_put(asoc);
         return NULL;
@@ -463,7 +485,6 @@ out:
 void sctp_err_finish(struct sock *sk, struct sctp_association *asoc)
 {
         sctp_bh_unlock_sock(sk);
-        sock_put(sk);
         if (asoc)
                 sctp_association_put(asoc);
 }
@@ -716,7 +737,6 @@ static struct sctp_endpoint *__sctp_rcv_lookup_endpoint(const union sctp_addr *l
 
 hit:
         sctp_endpoint_hold(ep);
-        sock_hold(epb->sk);
         read_unlock(&head->lock);
         return ep;
 }
@@ -818,7 +838,6 @@ static struct sctp_association *__sctp_lookup_association(
 hit:
         *pt = transport;
         sctp_association_hold(asoc);
-        sock_hold(epb->sk);
         read_unlock(&head->lock);
         return asoc;
 }
@@ -846,7 +865,6 @@ int sctp_has_association(const union sctp_addr *laddr,
         struct sctp_transport *transport;
 
         if ((asoc = sctp_lookup_association(laddr, paddr, &transport))) {
-                sock_put(asoc->base.sk);
                 sctp_association_put(asoc);
                 return 1;
         }
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 90863307bcd9..b1a17758003a 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1229,7 +1229,7 @@ SCTP_STATIC void sctp_close(struct sock *sk, long timeout)
 
         ep = sctp_sk(sk)->ep;
 
-        /* Walk all associations on a socket, not on an endpoint.  */
+        /* Walk all associations on an endpoint.  */
         list_for_each_safe(pos, temp, &ep->asocs) {
                 asoc = list_entry(pos, struct sctp_association, asocs);
 
@@ -5318,6 +5318,7 @@ static int sctp_wait_for_sndbuf(struct sctp_association *asoc, long *timeo_p,
                  */
                 sctp_release_sock(sk);
                 current_timeo = schedule_timeout(current_timeo);
+                BUG_ON(sk != asoc->base.sk);
                 sctp_lock_sock(sk);
 
                 *timeo_p = current_timeo;
@@ -5605,12 +5606,14 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
          */
         newsp->type = type;
 
-        spin_lock_bh(&oldsk->sk_lock.slock);
-        /* Migrate the backlog from oldsk to newsk. */
-        sctp_backlog_migrate(assoc, oldsk, newsk);
-        /* Migrate the association to the new socket. */
+        /* Mark the new socket "in-use" by the user so that any packets
+         * that may arrive on the association after we've moved it are
+         * queued to the backlog.  This prevents a potential race between
+         * backlog processing on the old socket and new-packet processing
+         * on the new socket.
+         */
+        sctp_lock_sock(newsk);
         sctp_assoc_migrate(assoc, newsk);
-        spin_unlock_bh(&oldsk->sk_lock.slock);
 
         /* If the association on the newsk is already closed before accept()
          * is called, set RCV_SHUTDOWN flag.
@@ -5619,6 +5622,7 @@ static void sctp_sock_migrate(struct sock *oldsk, struct sock *newsk,
                 newsk->sk_shutdown |= RCV_SHUTDOWN;
 
         newsk->sk_state = SCTP_SS_ESTABLISHED;
+        sctp_release_sock(newsk);
 }
 
 /* This proto struct describes the ULP interface for SCTP.  */