From d42eed4a044e5e10dfb885cf9891c2518a72a491 Mon Sep 17 00:00:00 2001 From: Florian Weimer 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. --- ChangeLog | 8 ++++++ sunrpc/Makefile | 3 +- sunrpc/clnt_udp.c | 2 +- sunrpc/tst-udp-error.c | 62 ++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 73 insertions(+), 2 deletions(-) create mode 100644 sunrpc/tst-udp-error.c diff --git a/ChangeLog b/ChangeLog index eeccfed101..a64fff8c6b 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2017-02-27 Florian Weimer + + [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 * sysdeps/generic/math_private.h: Use __BIG_ENDIAN and diff --git a/sunrpc/Makefile b/sunrpc/Makefile index 0c1e6124ff..daf8a28f1a 100644 --- a/sunrpc/Makefile +++ b/sunrpc/Makefile @@ -93,7 +93,7 @@ rpcgen-objs = rpc_main.o rpc_hout.o rpc_cout.o rpc_parse.o \ extra-objs = $(rpcgen-objs) $(addprefix cross-,$(rpcgen-objs)) others += rpcgen -tests = tst-xdrmem tst-xdrmem2 test-rpcent +tests = tst-xdrmem tst-xdrmem2 test-rpcent tst-udp-error xtests := tst-getmyaddr ifeq ($(have-thread-library),yes) @@ -155,6 +155,7 @@ BUILD_CPPFLAGS += $(sunrpc-CPPFLAGS) $(objpfx)tst-getmyaddr: $(common-objpfx)linkobj/libc.so $(objpfx)tst-xdrmem: $(common-objpfx)linkobj/libc.so $(objpfx)tst-xdrmem2: $(common-objpfx)linkobj/libc.so +$(objpfx)tst-udp-error: $(common-objpfx)linkobj/libc.so $(objpfx)rpcgen: $(addprefix $(objpfx),$(rpcgen-objs)) diff --git a/sunrpc/clnt_udp.c b/sunrpc/clnt_udp.c index 4d9acb1e6a..1de25cb771 100644 --- a/sunrpc/clnt_udp.c +++ b/sunrpc/clnt_udp.c @@ -421,9 +421,9 @@ 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 --git a/sunrpc/tst-udp-error.c b/sunrpc/tst-udp-error.c new file mode 100644 index 0000000000..1efc02f5c6 --- /dev/null +++ b/sunrpc/tst-udp-error.c @@ -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 + . */ + +#include +#include +#include +#include +#include +#include +#include + +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 -- 2.43.5