@@ -50,7 +50,10 @@
 #ifndef __KSELFTEST_HARNESS_H
 #define __KSELFTEST_HARNESS_H
 
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE
+#endif
+
 #include <asm/types.h>
 #include <errno.h>
 #include <stdbool.h>

@@ -1,7 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-or-later
 
 CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
-TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test
+LDLIBS += -lcap
+TEST_GEN_PROGS := openat2_test resolve_test rename_attack_test omayexec_test
 
 include ../lib.mk
 

@@ -0,0 +1 @@
+CONFIG_SYSCTL=y

@@ -9,6 +9,7 @@
 
 #define _GNU_SOURCE
 #include <stdint.h>
+#include <stdbool.h>
 #include <errno.h>
 #include <linux/types.h>
 #include "../kselftest.h"

@@ -0,0 +1,325 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test O_MAYEXEC
+ *
+ * Copyright © 2018-2020 ANSSI
+ *
+ * Author: Mickaël Salaün <mic@digikod.net>
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/capability.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <unistd.h>
+
+#include "helpers.h"
+#include "../kselftest_harness.h"
+
+#ifndef O_MAYEXEC
+#define O_MAYEXEC		040000000
+#endif
+
+static const char sysctl_path[] = "/proc/sys/fs/open_mayexec_enforce";
+
+static const char workdir_path[] = "./test-mount";
+static const char reg_file_path[] = "./test-mount/regular_file";
+static const char dir_path[] = "./test-mount/directory";
+static const char symlink_path[] = "./test-mount/symlink";
+static const char block_dev_path[] = "./test-mount/block_device";
+static const char char_dev_path[] = "./test-mount/character_device";
+static const char fifo_path[] = "./test-mount/fifo";
+static const char sock_path[] = "./test-mount/socket";
+
+static void ignore_dac(struct __test_metadata *_metadata, int override)
+{
+	cap_t caps;
+	const cap_value_t cap_val[2] = {
+		CAP_DAC_OVERRIDE,
+		CAP_DAC_READ_SEARCH,
+	};
+
+	caps = cap_get_proc();
+	ASSERT_NE(NULL, caps);
+	ASSERT_EQ(0, cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_val,
+				override ? CAP_SET : CAP_CLEAR));
+	ASSERT_EQ(0, cap_set_proc(caps));
+	EXPECT_EQ(0, cap_free(caps));
+}
+
+static void ignore_sys_admin(struct __test_metadata *_metadata, int override)
+{
+	cap_t caps;
+	const cap_value_t cap_val[1] = {
+		CAP_SYS_ADMIN,
+	};
+
+	caps = cap_get_proc();
+	ASSERT_NE(NULL, caps);
+	ASSERT_EQ(0, cap_set_flag(caps, CAP_EFFECTIVE, 1, cap_val,
+				override ? CAP_SET : CAP_CLEAR));
+	ASSERT_EQ(0, cap_set_proc(caps));
+	EXPECT_EQ(0, cap_free(caps));
+}
+
+static void test_omx(struct __test_metadata *_metadata,
+		const char *const path, const int no_mayexec_err_code,
+		const int mayexec_err_code)
+{
+	struct open_how how = {
+		.flags = O_RDONLY | O_NOFOLLOW | O_CLOEXEC,
+	};
+	int fd;
+
+	/* Do not block on pipes. */
+	if (path == fifo_path)
+		how.flags |= O_NONBLOCK;
+
+	/* Opens without O_MAYEXEC. */
+	fd = sys_openat2(AT_FDCWD, path, &how);
+	if (!no_mayexec_err_code) {
+		ASSERT_LE(0, fd) {
+			TH_LOG("Failed to openat2 %s: %d", path, -fd);
+		}
+		EXPECT_EQ(0, close(fd));
+	} else {
+		ASSERT_EQ(no_mayexec_err_code, fd) {
+			TH_LOG("Wrong error for openat2 %s: %d", path, -fd);
+		}
+	}
+
+	how.flags |= O_MAYEXEC;
+
+	/* Checks that O_MAYEXEC is ignored with open(2). */
+	fd = open(path, how.flags);
+	if (!no_mayexec_err_code) {
+		ASSERT_LE(0, fd) {
+			TH_LOG("Failed to open %s: %d", path, errno);
+		}
+		EXPECT_EQ(0, close(fd));
+	} else {
+		ASSERT_EQ(no_mayexec_err_code, -errno);
+	}
+
+	/* Checks that O_MAYEXEC is ignored with openat(2). */
+	fd = openat(AT_FDCWD, path, how.flags);
+	if (!no_mayexec_err_code) {
+		ASSERT_LE(0, fd) {
+			TH_LOG("Failed to openat %s: %d", path, errno);
+		}
+		EXPECT_EQ(0, close(fd));
+	} else {
+		ASSERT_EQ(no_mayexec_err_code, -errno);
+	}
+
+	/* Opens with O_MAYEXEC. */
+	fd = sys_openat2(AT_FDCWD, path, &how);
+	if (!mayexec_err_code) {
+		ASSERT_LE(0, fd) {
+			TH_LOG("Failed to openat2 %s: %d", path, -fd);
+		}
+		EXPECT_EQ(0, close(fd));
+	} else {
+		ASSERT_EQ(mayexec_err_code, fd) {
+			TH_LOG("Wrong error for openat2 %s: %d", path, -fd);
+		}
+	}
+}
+
+static void test_file_types(struct __test_metadata *_metadata, const int err_code,
+		const bool has_policy)
+{
+	test_omx(_metadata, reg_file_path, 0, err_code);
+	test_omx(_metadata, dir_path, 0, -EISDIR);
+	test_omx(_metadata, symlink_path, -ELOOP, -ELOOP);
+	test_omx(_metadata, block_dev_path, 0, has_policy ? -EACCES : 0);
+	test_omx(_metadata, char_dev_path, 0, has_policy ? -EACCES : 0);
+	test_omx(_metadata, fifo_path, 0, has_policy ? -EACCES : 0);
+	test_omx(_metadata, sock_path, -ENXIO, has_policy ? -EACCES : -ENXIO);
+}
+
+static void test_files(struct __test_metadata *_metadata, const int err_code,
+		const bool has_policy)
+{
+	/* Tests as root. */
+	ignore_dac(_metadata, 1);
+	test_file_types(_metadata, err_code, has_policy);
+
+	/* Tests without bypass. */
+	ignore_dac(_metadata, 0);
+	test_file_types(_metadata, err_code, has_policy);
+}
+
+static void sysctl_write_char(struct __test_metadata *_metadata, const char value)
+{
+	int fd;
+
+	fd = open(sysctl_path, O_WRONLY | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+	ASSERT_EQ(1, write(fd, &value, 1));
+	EXPECT_EQ(0, close(fd));
+}
+
+static char sysctl_read_char(struct __test_metadata *_metadata)
+{
+	int fd;
+	char sysctl_value;
+
+	fd = open(sysctl_path, O_RDONLY | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+	ASSERT_EQ(1, read(fd, &sysctl_value, 1));
+	EXPECT_EQ(0, close(fd));
+	return sysctl_value;
+}
+
+FIXTURE(omayexec) {
+	char initial_sysctl_value;
+};
+
+FIXTURE_VARIANT(omayexec) {
+	const bool mount_exec;
+	const bool file_exec;
+	const int sysctl_err_code[3];
+};
+
+FIXTURE_VARIANT_ADD(omayexec, mount_exec_file_exec) {
+	.mount_exec = true,
+	.file_exec = true,
+	.sysctl_err_code = {0, 0, 0},
+};
+
+FIXTURE_VARIANT_ADD(omayexec, mount_exec_file_noexec)
+{
+	.mount_exec = true,
+	.file_exec = false,
+	.sysctl_err_code = {0, -EACCES, -EACCES},
+};
+
+FIXTURE_VARIANT_ADD(omayexec, mount_noexec_file_exec)
+{
+	.mount_exec = false,
+	.file_exec = true,
+	.sysctl_err_code = {-EACCES, 0, -EACCES},
+};
+
+FIXTURE_VARIANT_ADD(omayexec, mount_noexec_file_noexec)
+{
+	.mount_exec = false,
+	.file_exec = false,
+	.sysctl_err_code = {-EACCES, -EACCES, -EACCES},
+};
+
+FIXTURE_SETUP(omayexec)
+{
+	/*
+	 * Cleans previous workspace if any error previously happened (don't
+	 * check errors).
+	 */
+	umount(workdir_path);
+	rmdir(workdir_path);
+
+	/* Creates a clean mount point. */
+	ASSERT_EQ(0, mkdir(workdir_path, 00700));
+	ASSERT_EQ(0, mount("test", workdir_path, "tmpfs", MS_MGC_VAL |
+				(variant->mount_exec ? 0 : MS_NOEXEC),
+				"mode=0700,size=4k"));
+
+	/* Creates a regular file. */
+	ASSERT_EQ(0, mknod(reg_file_path, S_IFREG | (variant->file_exec ? 0500 : 0400), 0));
+	/* Creates a directory. */
+	ASSERT_EQ(0, mkdir(dir_path, variant->file_exec ? 0500 : 0400));
+	/* Creates a symlink pointing to the regular file. */
+	ASSERT_EQ(0, symlink("regular_file", symlink_path));
+	/* Creates a character device: /dev/null. */
+	ASSERT_EQ(0, mknod(char_dev_path, S_IFCHR | 0400, makedev(1, 3)));
+	/* Creates a block device: /dev/loop0 */
+	ASSERT_EQ(0, mknod(block_dev_path, S_IFBLK | 0400, makedev(7, 0)));
+	/* Creates a fifo. */
+	ASSERT_EQ(0, mknod(fifo_path, S_IFIFO | 0400, 0));
+	/* Creates a socket. */
+	ASSERT_EQ(0, mknod(sock_path, S_IFSOCK | 0400, 0));
+
+	/* Saves initial sysctl value. */
+	self->initial_sysctl_value = sysctl_read_char(_metadata);
+
+	/* Prepares for sysctl writes. */
+	ignore_sys_admin(_metadata, 1);
+}
+
+FIXTURE_TEARDOWN(omayexec)
+{
+	/* Restores initial sysctl value. */
+	sysctl_write_char(_metadata, self->initial_sysctl_value);
+
+	/* There is no need to unlink the test files. */
+	ASSERT_EQ(0, umount(workdir_path));
+	ASSERT_EQ(0, rmdir(workdir_path));
+}
+
+TEST_F(omayexec, sysctl_0)
+{
+	/* Do not enforce anything. */
+	sysctl_write_char(_metadata, '0');
+	test_files(_metadata, 0, false);
+}
+
+TEST_F(omayexec, sysctl_1)
+{
+	/* Enforces mount exec check. */
+	sysctl_write_char(_metadata, '1');
+	test_files(_metadata, variant->sysctl_err_code[0], true);
+}
+
+TEST_F(omayexec, sysctl_2)
+{
+	/* Enforces file exec check. */
+	sysctl_write_char(_metadata, '2');
+	test_files(_metadata, variant->sysctl_err_code[1], true);
+}
+
+TEST_F(omayexec, sysctl_3)
+{
+	/* Enforces mount and file exec check. */
+	sysctl_write_char(_metadata, '3');
+	test_files(_metadata, variant->sysctl_err_code[2], true);
+}
+
+FIXTURE(cleanup) {
+	char initial_sysctl_value;
+};
+
+FIXTURE_SETUP(cleanup)
+{
+	/* Saves initial sysctl value. */
+	self->initial_sysctl_value = sysctl_read_char(_metadata);
+}
+
+FIXTURE_TEARDOWN(cleanup)
+{
+	/* Restores initial sysctl value. */
+	ignore_sys_admin(_metadata, 1);
+	sysctl_write_char(_metadata, self->initial_sysctl_value);
+}
+
+TEST_F(cleanup, sysctl_access_write)
+{
+	int fd;
+	ssize_t ret;
+
+	ignore_sys_admin(_metadata, 1);
+	sysctl_write_char(_metadata, '0');
+
+	ignore_sys_admin(_metadata, 0);
+	fd = open(sysctl_path, O_WRONLY | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+	ret = write(fd, "0", 1);
+	ASSERT_EQ(-1, ret);
+	ASSERT_EQ(EPERM, errno);
+	EXPECT_EQ(0, close(fd));
+}
+
+TEST_HARNESS_MAIN