[PATCH v2 4/4] CVE-2022-23218: Buffer overflow in sunrpc svcunix_create (bug 28768)

[Florian Weimer <fweimer@redhat.com>]

The sunrpc function svcunix_create suffers from a stack-based buffer
overflow with overlong pathname arguments.
---
 NEWS                  |  3 +++
 sunrpc/Makefile       |  2 +-
 sunrpc/svc_unix.c     | 11 ++++-------
 sunrpc/tst-bug28768.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 50 insertions(+), 8 deletions(-)
 create mode 100644 sunrpc/tst-bug28768.c

diff --git a/NEWS b/NEWS
index 94248b580d..85ec7e4c6a 100644
--- a/NEWS
+++ b/NEWS
@@ -154,6 +154,9 @@ Security related changes:
   legacy function could result in a stack-based buffer overflow when
   using the "unix" protocol.  Reported by Martin Sebor.
 
+  CVE-2022-23218: Passing an overlong file name to the svcunix_create
+  legacy function could result in a stack-based buffer overflow.
+
 The following bugs are resolved with this release:
 
   [The release manager will add the list generated by
diff --git a/sunrpc/Makefile b/sunrpc/Makefile
index 183ef3dc55..a79a7195fc 100644
--- a/sunrpc/Makefile
+++ b/sunrpc/Makefile
@@ -65,7 +65,7 @@ shared-only-routines = $(routines)
 endif
 
 tests = tst-xdrmem tst-xdrmem2 test-rpcent tst-udp-error tst-udp-timeout \
-  tst-udp-nonblocking tst-bug22542
+  tst-udp-nonblocking tst-bug22542 tst-bug28768
 
 xtests := tst-getmyaddr
 
diff --git a/sunrpc/svc_unix.c b/sunrpc/svc_unix.c
index f2280b4c49..67177a2e78 100644
--- a/sunrpc/svc_unix.c
+++ b/sunrpc/svc_unix.c
@@ -154,7 +154,10 @@ svcunix_create (int sock, u_int sendsize, u_int recvsize, char *path)
   SVCXPRT *xprt;
   struct unix_rendezvous *r;
   struct sockaddr_un addr;
-  socklen_t len = sizeof (struct sockaddr_in);
+  socklen_t len = sizeof (addr);
+
+  if (__sockaddr_un_set (&addr, path) < 0)
+    return NULL;
 
   if (sock == RPC_ANYSOCK)
     {
@@ -165,12 +168,6 @@ svcunix_create (int sock, u_int sendsize, u_int recvsize, char *path)
 	}
       madesock = TRUE;
     }
-  memset (&addr, '\0', sizeof (addr));
-  addr.sun_family = AF_UNIX;
-  len = strlen (path) + 1;
-  memcpy (addr.sun_path, path, len);
-  len += sizeof (addr.sun_family);
-
   __bind (sock, (struct sockaddr *) &addr, len);
 
   if (__getsockname (sock, (struct sockaddr *) &addr, &len) != 0
diff --git a/sunrpc/tst-bug28768.c b/sunrpc/tst-bug28768.c
new file mode 100644
index 0000000000..35a4b7b0b3
--- /dev/null
+++ b/sunrpc/tst-bug28768.c
@@ -0,0 +1,42 @@
+/* Test to verify that long path is rejected by svcunix_create (bug 28768).
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <rpc/svc.h>
+#include <shlib-compat.h>
+#include <string.h>
+#include <support/check.h>
+
+/* svcunix_create does not have a default version in linkobj/libc.so.  */
+compat_symbol_reference (libc, svcunix_create, svcunix_create, GLIBC_2_1);
+
+static int
+do_test (void)
+{
+  char pathname[109];
+  memset (pathname, 'x', sizeof (pathname));
+  pathname[sizeof (pathname) - 1] = '\0';
+
+  errno = 0;
+  TEST_VERIFY (svcunix_create (RPC_ANYSOCK, 4096, 4096, pathname) == NULL);
+  TEST_COMPARE (errno, EINVAL);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.34.1