From d42eed4a044e5e10dfb885cf9891c2518a72a491 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Mon, 27 Feb 2017 19:05:13 +0100
Subject: [PATCH] sunrpc: Avoid use-after-free read access in clntudp_call [BZ
#21115]
After commit bc779a1a5b3035133024b21e2f339fe4219fb11c
(CVE-2016-4429: sunrpc: Do not use alloca in clntudp_call
[BZ #20112]), ancillary data is stored on the heap,
but it is accessed after it has been freed.
The test case must be run under a heap debugger such as valgrind
to observe the invalid access. A malloc implementation which
immediately calls munmap on free would catch this bug as well.
---
sunrpc/Makefile | 3 +-
sunrpc/clnt_udp.c | 2 -
sunrpc/tst-udp-error.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 65 insertions(+), 2 deletions(-)
#diff --git a/ChangeLog b/ChangeLog
#index eeccfed101..a64fff8c6b 100644
#--- a/ChangeLog
##+++ b/ChangeLog
#@@ -1,3 +1,11 @@
#+2017-02-27 Florian Weimer <fweimer@redhat.com>
#+
#+ [BZ #21115]
#+ * sunrpc/clnt_udp.c (clntudp_call): Free ancillary data later.
#+ * sunrpc/Makefile (tests): Add tst-udp-error.
#+ (tst-udp-error): Link against libc.so explicitly.
#+ * sunrpc/tst-udp-error: New file.
#+
# 2017-02-25 Zack Weinberg <zackw@panix.com>
#
# * sysdeps/generic/math_private.h: Use __BIG_ENDIAN and
diff -Nurp glibc-2.22.old/sunrpc/clnt_udp.c glibc-2.22/sunrpc/clnt_udp.c
--- glibc-2.22.old/sunrpc/clnt_udp.c 2017-12-16 00:58:28.783564209 +0200
+++ glibc-2.22/sunrpc/clnt_udp.c 2017-12-16 01:20:45.777121947 +0200
@@ -453,9 +453,9 @@ send_again:
cmsg = CMSG_NXTHDR (&msg, cmsg))
if (cmsg->cmsg_level == SOL_IP && cmsg->cmsg_type == IP_RECVERR)
{
- free (cbuf);
e = (struct sock_extended_err *) CMSG_DATA(cmsg);
cu->cu_error.re_errno = e->ee_errno;
+ free (cbuf);
return (cu->cu_error.re_status = RPC_CANTRECV);
}
free (cbuf);
diff -Nurp glibc-2.22.old/sunrpc/Makefile glibc-2.22/sunrpc/Makefile
--- glibc-2.22.old/sunrpc/Makefile 2017-12-16 00:58:28.803564502 +0200
+++ glibc-2.22/sunrpc/Makefile 2017-12-16 01:24:03.052002902 +0200
@@ -96,7 +96,7 @@ rpcgen-objs = rpc_main.o rpc_hout.o rpc_
extra-objs = $(rpcgen-objs) $(addprefix cross-,$(rpcgen-objs))
others += rpcgen
-tests = tst-xdrmem tst-xdrmem2 test-rpcent tst-xdrmem3
+tests = tst-xdrmem tst-xdrmem2 test-rpcent tst-xdrmem3 tst-udp-error
xtests := tst-getmyaddr
tests-special += $(objpfx)mtrace-tst-xdrmem3.out
@@ -161,6 +161,7 @@ $(objpfx)tst-getmyaddr: $(common-objpfx)
$(objpfx)tst-xdrmem: $(common-objpfx)linkobj/libc.so
$(objpfx)tst-xdrmem2: $(common-objpfx)linkobj/libc.so
$(objpfx)tst-xdrmem3: $(common-objpfx)linkobj/libc.so
+$(objpfx)tst-udp-error: $(common-objpfx)linkobj/libc.so
$(objpfx)rpcgen: $(addprefix $(objpfx),$(rpcgen-objs))
diff -Nurp glibc-2.22.old/sunrpc/tst-udp-error.c glibc-2.22/sunrpc/tst-udp-error.c
--- glibc-2.22.old/sunrpc/tst-udp-error.c 1970-01-01 02:00:00.000000000 +0200
+++ glibc-2.22/sunrpc/tst-udp-error.c 2017-12-16 01:20:45.777121947 +0200
@@ -0,0 +1,62 @@
+/* Check for use-after-free in clntudp_call (bug 21115).
+ Copyright (C) 2017 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 <netinet/in.h>
+#include <rpc/clnt.h>
+#include <rpc/svc.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/xsocket.h>
+#include <unistd.h>
+
+static int
+do_test (void)
+{
+ support_become_root ();
+ support_enter_network_namespace ();
+
+ /* Obtain a likely-unused port number. */
+ struct sockaddr_in sin =
+ {
+ .sin_family = AF_INET,
+ .sin_addr.s_addr = htonl (INADDR_LOOPBACK),
+ };
+ {
+ int fd = xsocket (AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+ xbind (fd, (struct sockaddr *) &sin, sizeof (sin));
+ socklen_t sinlen = sizeof (sin);
+ xgetsockname (fd, (struct sockaddr *) &sin, &sinlen);
+ /* Close the socket, so that we will receive an error below. */
+ close (fd);
+ }
+
+ int sock = RPC_ANYSOCK;
+ CLIENT *clnt = clntudp_create
+ (&sin, 1, 2, (struct timeval) { 1, 0 }, &sock);
+ TEST_VERIFY_EXIT (clnt != NULL);
+ TEST_VERIFY (clnt_call (clnt, 3,
+ (xdrproc_t) xdr_void, NULL,
+ (xdrproc_t) xdr_void, NULL,
+ ((struct timeval) { 3, 0 }))
+ == RPC_CANTRECV);
+ clnt_destroy (clnt);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
