tcp: properly handle md5sig_pool references

tcp_v4_clear_md5_list() assumes that multiple tcp md5sig peers
only hold one reference to md5sig_pool. but tcp_v4_md5_do_add()
increases use count of md5sig_pool for each peer. This patch
makes tcp_v4_md5_do_add() only increases use count for the first
tcp md5sig peer.

Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/tcp_ipv4.c

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index c34f015..7963e03 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -927,18 +927,21 @@
 			}
 			sk_nocaps_add(sk, NETIF_F_GSO_MASK);
 		}
-		if (tcp_alloc_md5sig_pool(sk) == NULL) {
+
+		md5sig = tp->md5sig_info;
+		if (md5sig->entries4 == 0 &&
+		    tcp_alloc_md5sig_pool(sk) == NULL) {
 			kfree(newkey);
 			return -ENOMEM;
 		}
-		md5sig = tp->md5sig_info;
 
 		if (md5sig->alloced4 == md5sig->entries4) {
 			keys = kmalloc((sizeof(*keys) *
 					(md5sig->entries4 + 1)), GFP_ATOMIC);
 			if (!keys) {
 				kfree(newkey);
-				tcp_free_md5sig_pool();
+				if (md5sig->entries4 == 0)
+					tcp_free_md5sig_pool();
 				return -ENOMEM;
 			}
 
@@ -982,6 +985,7 @@
 				kfree(tp->md5sig_info->keys4);
 				tp->md5sig_info->keys4 = NULL;
 				tp->md5sig_info->alloced4 = 0;
+				tcp_free_md5sig_pool();
 			} else if (tp->md5sig_info->entries4 != i) {
 				/* Need to do some manipulation */
 				memmove(&tp->md5sig_info->keys4[i],
@@ -989,7 +993,6 @@
 					(tp->md5sig_info->entries4 - i) *
 					 sizeof(struct tcp4_md5sig_key));
 			}
-			tcp_free_md5sig_pool();
 			return 0;
 		}
 	}

net/ipv6/tcp_ipv6.c

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 79cc646..7b8fc57 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -591,7 +591,8 @@
 			}
 			sk_nocaps_add(sk, NETIF_F_GSO_MASK);
 		}
-		if (tcp_alloc_md5sig_pool(sk) == NULL) {
+		if (tp->md5sig_info->entries6 == 0 &&
+			tcp_alloc_md5sig_pool(sk) == NULL) {
 			kfree(newkey);
 			return -ENOMEM;
 		}
@@ -600,8 +601,9 @@
 				       (tp->md5sig_info->entries6 + 1)), GFP_ATOMIC);
 
 			if (!keys) {
-				tcp_free_md5sig_pool();
 				kfree(newkey);
+				if (tp->md5sig_info->entries6 == 0)
+					tcp_free_md5sig_pool();
 				return -ENOMEM;
 			}
 
@@ -647,6 +649,7 @@
 				kfree(tp->md5sig_info->keys6);
 				tp->md5sig_info->keys6 = NULL;
 				tp->md5sig_info->alloced6 = 0;
+				tcp_free_md5sig_pool();
 			} else {
 				/* shrink the database */
 				if (tp->md5sig_info->entries6 != i)
@@ -655,7 +658,6 @@
 						(tp->md5sig_info->entries6 - i)
 						* sizeof (tp->md5sig_info->keys6[0]));
 			}
-			tcp_free_md5sig_pool();
 			return 0;
 		}
 	}