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Message-ID: <202210281314.C5D3414722@keescook>
Date: Fri, 28 Oct 2022 13:16:43 -0700
From: Kees Cook <keescook@...omium.org>
To: Joey Gouly <joey.gouly@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Lennart Poettering <lennart@...ttering.net>,
Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>,
Alexander Viro <viro@...iv.linux.org.uk>,
Szabolcs Nagy <szabolcs.nagy@....com>,
Mark Brown <broonie@...nel.org>,
Jeremy Linton <jeremy.linton@....com>,
Topi Miettinen <toiwoton@...il.com>, linux-mm@...ck.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-abi-devel@...ts.sourceforge.net, nd@....com, shuah@...nel.org
Subject: Re: [PATCH v1 2/2] kselftest: vm: add tests for
memory-deny-write-execute
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@...omium.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@....com>
Signed-off-by: Joey Gouly <joey.gouly@....com>
Signed-off-by: Kees Cook <keescook@...omium.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
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