tools/testing/selftests/mm/mdwe_test.c

// SPDX-License-Identifier: GPL-2.0

#ifdef __aarch64__
#include <asm/hwcap.h>
#endif

#include <linux/mman.h>
#include <linux/prctl.h>

#include <stdio.h>
#include <stdlib.h>
#include <sys/auxv.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <unistd.h>

#include "../kselftest_harness.h"

#ifndef __aarch64__
# define PROT_BTI	0
#endif

TEST(prctl_flags)
{
	EXPECT_LT(prctl(PR_SET_MDWE, PR_MDWE_NO_INHERIT, 0L, 0L, 7L), 0);
	EXPECT_EQ(errno, EINVAL);

	EXPECT_LT(prctl(PR_SET_MDWE, 7L, 0L, 0L, 0L), 0);
	EXPECT_EQ(errno, EINVAL);
	EXPECT_LT(prctl(PR_SET_MDWE, 0L, 7L, 0L, 0L), 0);
	EXPECT_EQ(errno, EINVAL);
	EXPECT_LT(prctl(PR_SET_MDWE, 0L, 0L, 7L, 0L), 0);
	EXPECT_EQ(errno, EINVAL);
	EXPECT_LT(prctl(PR_SET_MDWE, 0L, 0L, 0L, 7L), 0);
	EXPECT_EQ(errno, EINVAL);

	EXPECT_LT(prctl(PR_GET_MDWE, 7L, 0L, 0L, 0L), 0);
	EXPECT_EQ(errno, EINVAL);
	EXPECT_LT(prctl(PR_GET_MDWE, 0L, 7L, 0L, 0L), 0);
	EXPECT_EQ(errno, EINVAL);
	EXPECT_LT(prctl(PR_GET_MDWE, 0L, 0L, 7L, 0L), 0);
	EXPECT_EQ(errno, EINVAL);
	EXPECT_LT(prctl(PR_GET_MDWE, 0L, 0L, 0L, 7L), 0);
	EXPECT_EQ(errno, EINVAL);
}

FIXTURE(consecutive_prctl_flags) {};
FIXTURE_SETUP(consecutive_prctl_flags) {}
FIXTURE_TEARDOWN(consecutive_prctl_flags) {}

FIXTURE_VARIANT(consecutive_prctl_flags)
{
	unsigned long first_flags;
	unsigned long second_flags;
	bool should_work;
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, can_keep_no_flags)
{
	.first_flags = 0,
	.second_flags = 0,
	.should_work = true,
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, can_keep_exec_gain)
{
	.first_flags = PR_MDWE_REFUSE_EXEC_GAIN,
	.second_flags = PR_MDWE_REFUSE_EXEC_GAIN,
	.should_work = true,
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, can_keep_both_flags)
{
	.first_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT,
	.second_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT,
	.should_work = true,
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_disable_mdwe)
{
	.first_flags = PR_MDWE_REFUSE_EXEC_GAIN,
	.second_flags = 0,
	.should_work = false,
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_disable_mdwe_no_inherit)
{
	.first_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT,
	.second_flags = 0,
	.should_work = false,
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_disable_no_inherit)
{
	.first_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT,
	.second_flags = PR_MDWE_REFUSE_EXEC_GAIN,
	.should_work = false,
};

FIXTURE_VARIANT_ADD(consecutive_prctl_flags, cant_enable_no_inherit)
{
	.first_flags = PR_MDWE_REFUSE_EXEC_GAIN,
	.second_flags = PR_MDWE_REFUSE_EXEC_GAIN | PR_MDWE_NO_INHERIT,
	.should_work = false,
};

TEST_F(consecutive_prctl_flags, two_prctls)
{
	int ret;

	EXPECT_EQ(prctl(PR_SET_MDWE, variant->first_flags, 0L, 0L, 0L), 0);

	ret = prctl(PR_SET_MDWE, variant->second_flags, 0L, 0L, 0L);
	if (variant->should_work) {
		EXPECT_EQ(ret, 0);

		ret = prctl(PR_GET_MDWE, 0L, 0L, 0L, 0L);
		ASSERT_EQ(ret, variant->second_flags);
	} else {
		EXPECT_NE(ret, 0);
		ASSERT_EQ(errno, EPERM);
	}
}

FIXTURE(mdwe)
{
	void *p;
	int flags;
	size_t size;
	pid_t pid;
};

FIXTURE_VARIANT(mdwe)
{
	bool enabled;
	bool forked;
	bool inherit;
};

FIXTURE_VARIANT_ADD(mdwe, stock)
{
	.enabled = false,
	.forked = false,
	.inherit = false,
};

FIXTURE_VARIANT_ADD(mdwe, enabled)
{
	.enabled = true,
	.forked = false,
	.inherit = true,
};

FIXTURE_VARIANT_ADD(mdwe, inherited)
{
	.enabled = true,
	.forked = true,
	.inherit = true,
};

FIXTURE_VARIANT_ADD(mdwe, not_inherited)
{
	.enabled = true,
	.forked = true,
	.inherit = false,
};

static bool executable_map_should_fail(const FIXTURE_VARIANT(mdwe) *variant)
{
	return variant->enabled && (!variant->forked || variant->inherit);
}

FIXTURE_SETUP(mdwe)
{
	unsigned long mdwe_flags;
	int ret, status;

	self->p = NULL;
	self->flags = MAP_SHARED | MAP_ANONYMOUS;
	self->size = getpagesize();

	if (!variant->enabled)
		return;

	mdwe_flags = PR_MDWE_REFUSE_EXEC_GAIN;
	if (!variant->inherit)
		mdwe_flags |= PR_MDWE_NO_INHERIT;

	ret = prctl(PR_SET_MDWE, mdwe_flags, 0L, 0L, 0L);
	ASSERT_EQ(ret, 0) {
		TH_LOG("PR_SET_MDWE failed or unsupported");
	}

	ret = prctl(PR_GET_MDWE, 0L, 0L, 0L, 0L);
	ASSERT_EQ(ret, mdwe_flags);

	if (variant->forked) {
		self->pid = fork();
		ASSERT_GE(self->pid, 0) {
			TH_LOG("fork failed\n");
		}

		if (self->pid > 0) {
			ret = waitpid(self->pid, &status, 0);
			ASSERT_TRUE(WIFEXITED(status));
			exit(WEXITSTATUS(status));
		}
	}
}

FIXTURE_TEARDOWN(mdwe)
{
	if (self->p && self->p != MAP_FAILED)
		munmap(self->p, self->size);
}

TEST_F(mdwe, mmap_READ_EXEC)
{
	self->p = mmap(NULL, self->size, PROT_READ | PROT_EXEC, self->flags, 0, 0);
	EXPECT_NE(self->p, MAP_FAILED);
}

TEST_F(mdwe, mmap_WRITE_EXEC)
{
	self->p = mmap(NULL, self->size, PROT_WRITE | PROT_EXEC, self->flags, 0, 0);
	if (executable_map_should_fail(variant)) {
		EXPECT_EQ(self->p, MAP_FAILED);
	} else {
		EXPECT_NE(self->p, MAP_FAILED);
	}
}

TEST_F(mdwe, mprotect_stay_EXEC)
{
	int ret;

	self->p = mmap(NULL, self->size, PROT_READ | PROT_EXEC, self->flags, 0, 0);
	ASSERT_NE(self->p, MAP_FAILED);

	ret = mprotect(self->p, self->size, PROT_READ | PROT_EXEC);
	EXPECT_EQ(ret, 0);
}

TEST_F(mdwe, mprotect_add_EXEC)
{
	int ret;

	self->p = mmap(NULL, self->size, PROT_READ, self->flags, 0, 0);
	ASSERT_NE(self->p, MAP_FAILED);

	ret = mprotect(self->p, self->size, PROT_READ | PROT_EXEC);
	if (executable_map_should_fail(variant)) {
		EXPECT_LT(ret, 0);
	} else {
		EXPECT_EQ(ret, 0);
	}
}

TEST_F(mdwe, mprotect_WRITE_EXEC)
{
	int ret;

	self->p = mmap(NULL, self->size, PROT_WRITE, self->flags, 0, 0);
	ASSERT_NE(self->p, MAP_FAILED);

	ret = mprotect(self->p, self->size, PROT_WRITE | PROT_EXEC);
	if (executable_map_should_fail(variant)) {
		EXPECT_LT(ret, 0);
	} else {
		EXPECT_EQ(ret, 0);
	}
}

TEST_F(mdwe, mmap_FIXED)
{
	void *p;

	self->p = mmap(NULL, self->size, PROT_READ, self->flags, 0, 0);
	ASSERT_NE(self->p, MAP_FAILED);

	/* MAP_FIXED unmaps the existing page before mapping which is allowed */
	p = mmap(self->p, self->size, PROT_READ | PROT_EXEC,
		 self->flags | MAP_FIXED, 0, 0);
	EXPECT_EQ(p, self->p);
}

TEST_F(mdwe, arm64_BTI)
{
	int ret;

#ifdef __aarch64__
	if (!(getauxval(AT_HWCAP2) & HWCAP2_BTI))
#endif
		SKIP(return, "HWCAP2_BTI not supported");

	self->p = mmap(NULL, self->size, PROT_EXEC, self->flags, 0, 0);
	ASSERT_NE(self->p, MAP_FAILED);

	ret = mprotect(self->p, self->size, PROT_EXEC | PROT_BTI);
	EXPECT_EQ(ret, 0);
}

TEST_HARNESS_MAIN