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Date:   Fri, 28 Oct 2022 13:16:43 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Joey Gouly <joey.gouly@arm.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Lennart Poettering <lennart@poettering.net>,
        Zbigniew =?utf-8?Q?J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Szabolcs Nagy <szabolcs.nagy@arm.com>,
        Mark Brown <broonie@kernel.org>,
        Jeremy Linton <jeremy.linton@arm.com>,
        Topi Miettinen <toiwoton@gmail.com>, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-abi-devel@lists.sourceforge.net, nd@arm.com, shuah@kernel.org
Subject: Re: [PATCH v1 2/2] kselftest: vm: add tests for
 memory-deny-write-execute
Message-ID: <202210281314.C5D3414722@keescook>
References: <20221026150457.36957-1-joey.gouly@arm.com>
 <20221026150457.36957-3-joey.gouly@arm.com>
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In-Reply-To: <20221026150457.36957-3-joey.gouly@arm.com>
Precedence: bulk

Here's an alternative rewritten to use kselftest_harness.h, with tests
for the prctl() flags, and the missed Makefile addition. This should be
much easier to add more variants and tests to, I hope.

-Kees

From bc442a99ebd9852bfaa7444b521bd55fdbb4d369 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Fri, 28 Oct 2022 13:10:45 -0700
Subject: [PATCH] selftests/vm: add tests for memory-deny-write-execute

Add tests for new prctl() commands, including flag values. Add tests for
new denials based on PROT_EXEC across mmap() and mprotect() with MDWE.

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>
---
 tools/testing/selftests/vm/Makefile    |   1 +
 tools/testing/selftests/vm/mdwe_test.c | 201 +++++++++++++++++++++++++
 2 files changed, 202 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 163c2fde3cb3..8dd4d4910fa5 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -52,6 +52,7 @@ TEST_GEN_FILES += userfaultfd
 TEST_GEN_PROGS += soft-dirty
 TEST_GEN_PROGS += split_huge_page_test
 TEST_GEN_FILES += ksm_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..d6f6b751bcd6
--- /dev/null
+++ b/tools/testing/selftests/vm/mdwe_test.c
@@ -0,0 +1,201 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifdef __aarch64__
+#include <asm/hwcap.h>
+#endif
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/auxv.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <linux/prctl.h>
+
+#include "../kselftest_harness.h"
+
+#define PR_SET_MDWE                     65
+# define PR_MDWE_FLAG_MMAP              1
+
+#define PR_GET_MDWE                     66
+
+#ifdef __aarch64__
+# define PROT_BTI	0x10            /* BTI guarded page */
+#else
+# define PROT_BTI	0
+#endif
+
+TEST(prctl_flags)
+{
+	EXPECT_LT(prctl(PR_SET_MDWE, 7, 0, 0, 0), 0);
+	EXPECT_LT(prctl(PR_SET_MDWE, 0, 7, 0, 0), 0);
+	EXPECT_LT(prctl(PR_SET_MDWE, 0, 0, 7, 0), 0);
+	EXPECT_LT(prctl(PR_SET_MDWE, 0, 0, 0, 7), 0);
+
+	EXPECT_LT(prctl(PR_GET_MDWE, 7, 0, 0, 0), 0);
+	EXPECT_LT(prctl(PR_GET_MDWE, 0, 7, 0, 0), 0);
+	EXPECT_LT(prctl(PR_GET_MDWE, 0, 0, 7, 0), 0);
+	EXPECT_LT(prctl(PR_GET_MDWE, 0, 0, 0, 7), 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_FLAG_MMAP, 0, 0, 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("PR_SET_MDWE failed or unsupported");
+	}
+
+	ret = prctl(PR_GET_MDWE, 0, 0, 0, 0);
+	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;
+
+	self->p = mmap(NULL, self->size, PROT_READ, self->flags, 0, 0);
+	ASSERT_NE(self->p, MAP_FAILED);
+
+	p = mmap(self->p, 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
-- 
2.34.1


-- 
Kees Cook