[LTP] [PATCH v3 2/9] Test for vulnerability CVE-2016-7117 in recvmmsg error return path

Richard Palethorpe
2017-06-23T12:22:04Z

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
---
configure.ac | 1 +
m4/ltp-mmsghdr.m4 | 22 ++++++
testcases/cve/cve-2016-7117.c | 158 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 181 insertions(+)
create mode 100644 m4/ltp-mmsghdr.m4
create mode 100644 testcases/cve/cve-2016-7117.c

diff --git a/configure.ac b/configure.ac
index cbe01d34f..326da8ece 100644
--- a/configure.ac
+++ b/configure.ac
@@ -192,5 +192,6 @@ LTP_CHECK_EPOLL_PWAIT
LTP_CHECK_KEYUTILS_SUPPORT
LTP_CHECK_SYNC_ADD_AND_FETCH
LTP_CHECK_BUILTIN_CLEAR_CACHE
+LTP_CHECK_MMSGHDR

AC_OUTPUT
diff --git a/m4/ltp-mmsghdr.m4 b/m4/ltp-mmsghdr.m4
new file mode 100644
index 000000000..05522180e
--- /dev/null
+++ b/m4/ltp-mmsghdr.m4
@@ -0,0 +1,22 @@
+dnl Copyright (c) 2017 Richard Palethorpe <rpalethorpe@suse.com>
+dnl
+dnl This program is free software; you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation; either version 2 of the License, or
+dnl (at your option) any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+dnl the GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+AC_DEFUN([LTP_CHECK_MMSGHDR],[
+AC_CHECK_TYPES([struct mmsghdr],,,[
+#define _GNU_SOURCE
+#include <sys/types.h>
+#include <sys/socket.h>
+])
+])
diff --git a/testcases/cve/cve-2016-7117.c b/testcases/cve/cve-2016-7117.c
new file mode 100644
index 000000000..25937edd1
--- /dev/null
+++ b/testcases/cve/cve-2016-7117.c
@@ -0,0 +1,158 @@
+/*
+ * Copyright (c) 2017 Richard Palethorpe <rpalethorpe@suse.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+/*
+ * CVE-2016-7117
+ *
+ * This tests for a use after free caused by a race between recvmmsg() and
+ * close(). The exit path for recvmmsg() in (a2e2725541f: net: Introduce
+ * recvmmsg socket syscall) called fput() on the active file descriptor before
+ * checking the error state and setting the socket's error field.
+ *
+ * If one or more messages are received by recvmmsg() followed by one which
+ * fails, the socket's error field will be set. If just after recvmmsg() calls
+ * fput(), a call to close() is made on the same file descriptor there is a
+ * race between close() releasing the socket object and recvmmsg() setting its
+ * error field.
+ *
+ * fput() does not release a file descriptor's resources (e.g. a socket)
+ * immediatly, it queues them to be released just before a system call returns
+ * to user land. So the close() system call must call fput() after it is
+ * called in recvmmsg(), exit and release the resources all before the socket
+ * error is set.
+ *
+ * Usually if the vulnerability is present the test will be killed with a
+ * kernel null pointer exception. However this is not guaranteed to happen
+ * every time.
+ *
+ * The following was used for reference
+ * https://blog.lizzie.io/notes-about-cve-2016-7117.html
+ */
+
+#include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/syscall.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#include "tst_test.h"
+#include "tst_safe_net.h"
+#include "tst_safe_pthread.h"
+#include "tst_timer.h"
+#include "tst_fuzzy_sync.h"
+
+/* The bug was present in the kernel before recvmmsg was exposed by glibc */
+#include "linux_syscall_numbers.h"
+
+#define MSG "abcdefghijklmnop"
+#define RECV_TIMEOUT 1
+#define ATTEMPTS 0x1FFFFF
+
+#ifndef HAVE_STRUCT_MMSGHDR
+struct mmsghdr {
+ struct msghdr msg_hdr;
+ unsigned int msg_len;
+};
+#endif
+
+static int socket_fds[2];
+static struct mmsghdr msghdrs[2] = {
+ {
+ .msg_hdr = {
+ .msg_iov = &(struct iovec) {
+ .iov_len = sizeof(MSG),
+ },
+ .msg_iovlen = 1
+ }
+ },
+ {
+ .msg_hdr = {
+ .msg_iov = &(struct iovec) {
+ .iov_base = (void *)(0xbadadd),
+ .iov_len = ~0,
+ },
+ .msg_iovlen = 1
+ }
+ }
+};
+static char rbuf[sizeof(MSG)];
+static struct timespec timeout = { .tv_sec = RECV_TIMEOUT };
+static struct tst_fzsync_pair fzsync_pair = TST_FZSYNC_PAIR_INIT;
+
+static void cleanup(void)
+{
+ close(socket_fds[0]);
+ close(socket_fds[1]);
+}
+
+static void *send_and_close(void *arg)
+{
+ send(socket_fds[0], MSG, sizeof(MSG), 0);
+ send(socket_fds[0], MSG, sizeof(MSG), 0);
+
+ tst_fzsync_delay_b(&fzsync_pair);
+
+ close(socket_fds[0]);
+ close(socket_fds[1]);
+ tst_fzsync_time_b(&fzsync_pair);
+
+ return arg;
+}
+
+static void run(void)
+{
+ pthread_t pt_send;
+ int i, stat, too_early_count = 0;
+
+ msghdrs[0].msg_hdr.msg_iov->iov_base = (void *)&rbuf;
+
+ for (i = 1; i < ATTEMPTS; i++) {
+ if (socketpair(AF_LOCAL, SOCK_DGRAM, 0, socket_fds))
+ tst_brk(TBROK | TERRNO, "Socket creation failed");
+
+ SAFE_PTHREAD_CREATE(&pt_send, 0, send_and_close, 0);
+
+ tst_fzsync_delay_a(&fzsync_pair);
+
+ stat = tst_syscall(__NR_recvmmsg,
+ socket_fds[1], msghdrs, 2, 0, &timeout);
+ tst_fzsync_time_a(&fzsync_pair);
+ if (stat < 0 && errno == EBADF)
+ too_early_count++;
+ else if (stat == 0)
+ tst_res(TWARN, "No messages received, should be one");
+ else if (stat < 0)
+ tst_res(TWARN | TERRNO, "recvmmsg failed unexpectedly");
+
+ SAFE_PTHREAD_JOIN(pt_send, 0);
+
+ tst_fzsync_pair_update(i, &fzsync_pair);
+ if (!(i & 0x7FFFF)) {
+ tst_res(TINFO, "Too early: %.1f%%",
+ 100 * too_early_count / (float)i);
+ tst_fzsync_pair_info(&fzsync_pair);
+ }
+ }
+
+ tst_res(TPASS, "Nothing happened after %d attempts", ATTEMPTS);
+}
+
+static struct tst_test test = {
+ .test_all = run,
+ .cleanup = cleanup,
+ .min_kver = "2.6.33",
+};
--
2.12.2