2 files changed, 17 insertions, 8 deletions

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 61d042bbbf60..68449293c4b6 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -163,6 +163,7 @@ struct dccp_request_sock {
         __u64                    dreq_isr;
         __u64                    dreq_gsr;
         __be32                   dreq_service;
+        spinlock_t               dreq_lock;
         struct list_head         dreq_featneg;
         __u32                    dreq_timestamp_echo;
         __u32                    dreq_timestamp_time;
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index e267e6f4c9a5..abd07a443219 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -142,6 +142,13 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
         struct dccp_request_sock *dreq = dccp_rsk(req);
         bool own_req;
 
+        /* TCP/DCCP listeners became lockless.
+         * DCCP stores complex state in its request_sock, so we need
+         * a protection for them, now this code runs without being protected
+         * by the parent (listener) lock.
+         */
+        spin_lock_bh(&dreq->dreq_lock);
+
         /* Check for retransmitted REQUEST */
         if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
 
@@ -156,7 +163,7 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
                         inet_rtx_syn_ack(sk, req);
                 }
                 /* Network Duplicate, discard packet */
-                return NULL;
+                goto out;
         }
 
         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
@@ -182,20 +189,20 @@ struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
 
         child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
                                                          req, &own_req);
-        if (!child)
-                goto listen_overflow;
-
-        return inet_csk_complete_hashdance(sk, child, req, own_req);
+        if (child) {
+                child = inet_csk_complete_hashdance(sk, child, req, own_req);
+                goto out;
+        }
 
-listen_overflow:
-        dccp_pr_debug("listen_overflow!\n");
         DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
 drop:
         if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
                 req->rsk_ops->send_reset(sk, skb);
 
         inet_csk_reqsk_queue_drop(sk, req);
-        return NULL;
+out:
+        spin_unlock_bh(&dreq->dreq_lock);
+        return child;
 }
 
 EXPORT_SYMBOL_GPL(dccp_check_req);
@@ -246,6 +253,7 @@ int dccp_reqsk_init(struct request_sock *req,
 {
         struct dccp_request_sock *dreq = dccp_rsk(req);
 
+        spin_lock_init(&dreq->dreq_lock);
         inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
         inet_rsk(req)->ir_num      = ntohs(dccp_hdr(skb)->dccph_dport);
         inet_rsk(req)->acked       = 0;