[PATCH v4 6/6] kselftest: vm: Add tests for no-inherit memory-deny-write-execute

[Florent Revest <revest@chromium.org>]

Add some tests to cover the new PR_MDWE_NO_INHERIT flag of the
PR_SET_MDWE prctl.

Check that:
- it can't be set without PR_SET_MDWE
- MDWE flags can't be unset
- when set, PR_SET_MDWE doesn't propagate to children

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Florent Revest <revest@chromium.org>
---
 tools/testing/selftests/mm/mdwe_test.c | 114 +++++++++++++++++++++++--
 1 file changed, 108 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/mm/mdwe_test.c b/tools/testing/selftests/mm/mdwe_test.c
index 1b84cf8e1bbe..200bedcdc32e 100644
--- a/tools/testing/selftests/mm/mdwe_test.c
+++ b/tools/testing/selftests/mm/mdwe_test.c
@@ -22,6 +22,9 @@
 
 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);
@@ -41,6 +44,84 @@ TEST(prctl_flags)
 	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;
@@ -53,28 +134,45 @@ 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, forked)
+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;
@@ -84,13 +182,17 @@ FIXTURE_SETUP(mdwe)
 	if (!variant->enabled)
 		return;
 
-	ret = prctl(PR_SET_MDWE, PR_MDWE_REFUSE_EXEC_GAIN, 0L, 0L, 0L);
+	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, 1);
+	ASSERT_EQ(ret, mdwe_flags);
 
 	if (variant->forked) {
 		self->pid = fork();
@@ -121,7 +223,7 @@ TEST_F(mdwe, mmap_READ_EXEC)
 TEST_F(mdwe, mmap_WRITE_EXEC)
 {
 	self->p = mmap(NULL, self->size, PROT_WRITE | PROT_EXEC, self->flags, 0, 0);
-	if (variant->enabled) {
+	if (executable_map_should_fail(variant)) {
 		EXPECT_EQ(self->p, MAP_FAILED);
 	} else {
 		EXPECT_NE(self->p, MAP_FAILED);
@@ -147,7 +249,7 @@ TEST_F(mdwe, mprotect_add_EXEC)
 	ASSERT_NE(self->p, MAP_FAILED);
 
 	ret = mprotect(self->p, self->size, PROT_READ | PROT_EXEC);
-	if (variant->enabled) {
+	if (executable_map_should_fail(variant)) {
 		EXPECT_LT(ret, 0);
 	} else {
 		EXPECT_EQ(ret, 0);
@@ -162,7 +264,7 @@ TEST_F(mdwe, mprotect_WRITE_EXEC)
 	ASSERT_NE(self->p, MAP_FAILED);
 
 	ret = mprotect(self->p, self->size, PROT_WRITE | PROT_EXEC);
-	if (variant->enabled) {
+	if (executable_map_should_fail(variant)) {
 		EXPECT_LT(ret, 0);
 	} else {
 		EXPECT_EQ(ret, 0);
-- 
2.42.0.rc2.253.gd59a3bf2b4-goog