netdev - Re: [PATCH iproute2] libnetlink: fix socket leak in rtnl_open

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Date:   Thu, 10 Feb 2022 17:19:03 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Maxim Petrov <mmrmaximuzz@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH iproute2] libnetlink: fix socket leak in
 rtnl_open_byproto()

On Tue, 8 Feb 2022 20:20:45 +0300
Maxim Petrov <mmrmaximuzz@...il.com> wrote:

> rtnl_open_byproto() does not close the opened socket in case of errors, and the
> socket is returned to the caller in the `fd` field of the struct. However, none
> of the callers care about the socket, so close it in the function immediately to
> avoid any potential resource leaks.
> 
> Signed-off-by: Maxim Petrov <mmrmaximuzz@...il.com>

Can do the same thing without introducing a goto

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 7e977a6762f8..0ed6d68b5c08 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -226,29 +226,26 @@ int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int subscriptions,
 	memset(&rth->local, 0, sizeof(rth->local));
 	rth->local.nl_family = AF_NETLINK;
 	rth->local.nl_groups = subscriptions;
+	addr_len = sizeof(rth->local);
 
 	if (bind(rth->fd, (struct sockaddr *)&rth->local,
 		 sizeof(rth->local)) < 0) {
 		perror("Cannot bind netlink socket");
-		return -1;
-	}
-	addr_len = sizeof(rth->local);
-	if (getsockname(rth->fd, (struct sockaddr *)&rth->local,
+	} else if (getsockname(rth->fd, (struct sockaddr *)&rth->local,
 			&addr_len) < 0) {
 		perror("Cannot getsockname");
-		return -1;
-	}
-	if (addr_len != sizeof(rth->local)) {
+	} else if (addr_len != sizeof(rth->local)) {
 		fprintf(stderr, "Wrong address length %d\n", addr_len);
-		return -1;
-	}
-	if (rth->local.nl_family != AF_NETLINK) {
+	} else if (rth->local.nl_family != AF_NETLINK) {
 		fprintf(stderr, "Wrong address family %d\n",
 			rth->local.nl_family);
-		return -1;
+	} else {
+		rth->seq = time(NULL);
+		return 0;
 	}
-	rth->seq = time(NULL);
-	return 0;
+
+	rtnl_close(rth);
+	return -1;
 }
 
 int rtnl_open(struct rtnl_handle *rth, unsigned int subscriptions)
-- 
2.34.1