Subject: [PATCH 2/4] sctp: refactor sctp_setsockopt_bindx

From: Christoph Hellwig <[email-masked]>
Date: Fri, 29 May 2020 14:09:41 +0200

Split out a sctp_setsockopt_bindx_kernel that takes a kernel pointer
to the sockaddr and make sctp_setsockopt_bindx a small wrapper around
it.  This prepares for adding a new bind_add proto op.

Signed-off-by: Christoph Hellwig <[email-masked]>
---
 net/sctp/socket.c | 61 ++++++++++++++++++++++-------------------------
 1 file changed, 28 insertions(+), 33 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 827a9903ee288..6e745ac3c4a59 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -972,23 +972,22 @@ int sctp_asconf_mgmt(struct sctp_sock *sp, struct sctp_sockaddr_entry *addrw)
  * it.
  *
  * sk        The sk of the socket
- * addrs     The pointer to the addresses in user land
+ * addrs     The pointer to the addresses
  * addrssize Size of the addrs buffer
  * op        Operation to perform (add or remove, see the flags of
  *           sctp_bindx)
  *
  * Returns 0 if ok, <0 errno code on error.
  */
-static int sctp_setsockopt_bindx(struct sock *sk,
-				 struct sockaddr __user *addrs,
-				 int addrs_size, int op)
+static int sctp_setsockopt_bindx_kernel(struct sock *sk,
+					struct sockaddr *addrs, int addrs_size,
+					int op)
 {
-	struct sockaddr *kaddrs;
 	int err;
 	int addrcnt = 0;
 	int walk_size = 0;
 	struct sockaddr *sa_addr;
-	void *addr_buf;
+	void *addr_buf = addrs;
 	struct sctp_af *af;
 
 	pr_debug("%s: sk:%p addrs:%p addrs_size:%d opt:%d\n",
@@ -997,17 +996,10 @@ static int sctp_setsockopt_bindx(struct sock *sk,
 	if (unlikely(addrs_size <= 0))
 		return -EINVAL;
 
-	kaddrs = memdup_user(addrs, addrs_size);
-	if (IS_ERR(kaddrs))
-		return PTR_ERR(kaddrs);
-
 	/* Walk through the addrs buffer and count the number of addresses. */
-	addr_buf = kaddrs;
 	while (walk_size < addrs_size) {
-		if (walk_size + sizeof(sa_family_t) > addrs_size) {
-			kfree(kaddrs);
+		if (walk_size + sizeof(sa_family_t) > addrs_size)
 			return -EINVAL;
-		}
 
 		sa_addr = addr_buf;
 		af = sctp_get_af_specific(sa_addr->sa_family);
@@ -1015,10 +1007,8 @@ static int sctp_setsockopt_bindx(struct sock *sk,
 		/* If the address family is not supported or if this address
 		 * causes the address buffer to overflow return EINVAL.
 		 */
-		if (!af || (walk_size + af->sockaddr_len) > addrs_size) {
-			kfree(kaddrs);
+		if (!af || (walk_size + af->sockaddr_len) > addrs_size)
 			return -EINVAL;
-		}
 		addrcnt++;
 		addr_buf += af->sockaddr_len;
 		walk_size += af->sockaddr_len;
@@ -1029,31 +1019,36 @@ static int sctp_setsockopt_bindx(struct sock *sk,
 	case SCTP_BINDX_ADD_ADDR:
 		/* Allow security module to validate bindx addresses. */
 		err = security_sctp_bind_connect(sk, SCTP_SOCKOPT_BINDX_ADD,
-						 (struct sockaddr *)kaddrs,
-						 addrs_size);
+						 addrs, addrs_size);
 		if (err)
-			goto out;
-		err = sctp_bindx_add(sk, kaddrs, addrcnt);
+			return err;
+		err = sctp_bindx_add(sk, addrs, addrcnt);
 		if (err)
-			goto out;
-		err = sctp_send_asconf_add_ip(sk, kaddrs, addrcnt);
-		break;
-
+			return err;
+		return sctp_send_asconf_add_ip(sk, addrs, addrcnt);
 	case SCTP_BINDX_REM_ADDR:
-		err = sctp_bindx_rem(sk, kaddrs, addrcnt);
+		err = sctp_bindx_rem(sk, addrs, addrcnt);
 		if (err)
-			goto out;
-		err = sctp_send_asconf_del_ip(sk, kaddrs, addrcnt);
-		break;
+			return err;
+		return sctp_send_asconf_del_ip(sk, addrs, addrcnt);
 
 	default:
-		err = -EINVAL;
-		break;
+		return -EINVAL;
 	}
+}
 
-out:
-	kfree(kaddrs);
+static int sctp_setsockopt_bindx(struct sock *sk,
+				 struct sockaddr __user *addrs,
+				 int addrs_size, int op)
+{
+	struct sockaddr *kaddrs;
+	int err;
 
+	kaddrs = memdup_user(addrs, addrs_size);
+	if (IS_ERR(kaddrs))
+		return PTR_ERR(kaddrs);
+	err = sctp_setsockopt_bindx_kernel(sk, kaddrs, addrs_size, op);
+	kfree(kaddrs);
 	return err;
 }
 
-- 
2.26.2