CVE-2022-23219: Buffer overflow in sunrpc clnt_create for "unix" (bug 22542)

Processing an overlong pathname in the sunrpc clnt_create function
results in a stack-based buffer overflow.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

NEWS

@@ -156,7 +156,9 @@ Changes to build and runtime requirements:
 
 Security related changes:
 
-  [Add security related changes here]
+  CVE-2022-23219: Passing an overlong file name to the clnt_create
+  legacy function could result in a stack-based buffer overflow when
+  using the "unix" protocol.  Reported by Martin Sebor.
 
 The following bugs are resolved with this release:
 

sunrpc/clnt_gen.c

@@ -57,9 +57,13 @@ clnt_create (const char *hostname, u_long prog, u_long vers,
 
   if (strcmp (proto, "unix") == 0)
     {
-      memset ((char *)&sun, 0, sizeof (sun));
-      sun.sun_family = AF_UNIX;
-      strcpy (sun.sun_path, hostname);
+      if (__sockaddr_un_set (&sun, hostname) < 0)
+	{
+	  struct rpc_createerr *ce = &get_rpc_createerr ();
+	  ce->cf_stat = RPC_SYSTEMERROR;
+	  ce->cf_error.re_errno = errno;
+	  return NULL;
+	}
       sock = RPC_ANYSOCK;
       client = clntunix_create (&sun, prog, vers, &sock, 0, 0);
       if (client == NULL)