[PATCH v2 2/2] kselftest: vm: add tests for memory-deny-write-execute

[Joey Gouly <joey.gouly@arm.com>]

From: Kees Cook <keescook@chromium.org>

Add some tests to cover the new PR_SET_MDWE prctl.

Co-developed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuah@kernel.org>
---
 tools/testing/selftests/vm/Makefile    |   1 +
 tools/testing/selftests/vm/mdwe_test.c | 197 +++++++++++++++++++++++++
 2 files changed, 198 insertions(+)
 create mode 100644 tools/testing/selftests/vm/mdwe_test.c

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 89c14e41bd43..4e1a7b1d4c52 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -56,6 +56,7 @@ TEST_GEN_PROGS += soft-dirty
 TEST_GEN_PROGS += split_huge_page_test
 TEST_GEN_FILES += ksm_tests
 TEST_GEN_PROGS += ksm_functional_tests
+TEST_GEN_PROGS += mdwe_test
 
 ifeq ($(MACHINE),x86_64)
 CAN_BUILD_I386 := $(shell ./../x86/check_cc.sh "$(CC)" ../x86/trivial_32bit_program.c -m32)
diff --git a/tools/testing/selftests/vm/mdwe_test.c b/tools/testing/selftests/vm/mdwe_test.c
new file mode 100644
index 000000000000..f466a099f1bf
--- /dev/null
+++ b/tools/testing/selftests/vm/mdwe_test.c
@@ -0,0 +1,197 @@
+// 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, 7L, 0L, 0L, 0L), 0);
+	EXPECT_LT(prctl(PR_SET_MDWE, 0L, 7L, 0L, 0L), 0);
+	EXPECT_LT(prctl(PR_SET_MDWE, 0L, 0L, 7L, 0L), 0);
+	EXPECT_LT(prctl(PR_SET_MDWE, 0L, 0L, 0L, 7L), 0);
+
+	EXPECT_LT(prctl(PR_GET_MDWE, 7L, 0L, 0L, 0L), 0);
+	EXPECT_LT(prctl(PR_GET_MDWE, 0L, 7L, 0L, 0L), 0);
+	EXPECT_LT(prctl(PR_GET_MDWE, 0L, 0L, 7L, 0L), 0);
+	EXPECT_LT(prctl(PR_GET_MDWE, 0L, 0L, 0L, 7L), 0);
+}
+
+FIXTURE(mdwe)
+{
+	void *p;
+	int flags;
+	size_t size;
+	pid_t pid;
+};
+
+FIXTURE_VARIANT(mdwe)
+{
+	bool enabled;
+	bool forked;
+};
+
+FIXTURE_VARIANT_ADD(mdwe, stock)
+{
+        .enabled = false,
+	.forked = false,
+};
+
+FIXTURE_VARIANT_ADD(mdwe, enabled)
+{
+        .enabled = true,
+	.forked = false,
+};
+
+FIXTURE_VARIANT_ADD(mdwe, forked)
+{
+        .enabled = true,
+	.forked = true,
+};
+
+FIXTURE_SETUP(mdwe)
+{
+	int ret, status;
+
+	self->p = NULL;
+	self->flags = MAP_SHARED | MAP_ANONYMOUS;
+	self->size = getpagesize();
+
+	if (!variant->enabled)
+		return;
+
+	ret = prctl(PR_SET_MDWE, PR_MDWE_REFUSE_EXEC_GAIN, 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, 1);
+
+	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 (variant->enabled) {
+		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 (variant->enabled) {
+		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 (variant->enabled) {
+		EXPECT_LT(ret, 0);
+	} else {
+		EXPECT_EQ(ret, 0);
+	}
+}
+
+TEST_F(mdwe, mmap_FIXED)
+{
+	void *p, *p2;
+
+	p2 = mmap(NULL, self->size, PROT_READ | PROT_EXEC, self->flags, 0, 0);
+	self->p = mmap(NULL, self->size, PROT_READ, self->flags, 0, 0);
+	ASSERT_NE(self->p, MAP_FAILED);
+
+	p = mmap(self->p + self->size, self->size, PROT_READ | PROT_EXEC,
+		 self->flags | MAP_FIXED, 0, 0);
+	if (variant->enabled) {
+		EXPECT_EQ(p, MAP_FAILED);
+	} else {
+		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
-- 
2.17.1