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From: jeffxu@chromium.org
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Cc: jeffxu@google.com,
	jorgelo@chromium.org,
	groeck@chromium.org,
	linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org,
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	=David.Laight@aculab.com,
	Jeff Xu <jeffxu@chromium.org>
Subject: [PATCH v9 5/5] selftest mm/mseal read-only elf memory segment
Date: Wed, 14 Feb 2024 15:11:29 +0000
Message-ID: <20240214151130.616240-6-jeffxu@chromium.org>
In-Reply-To: <20240214151130.616240-1-jeffxu@chromium.org>
References: <20240214151130.616240-1-jeffxu@chromium.org>
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From: Jeff Xu <jeffxu@chromium.org>

Sealing read-only of elf mapping so it can't be changed by mprotect.

Signed-off-by: Jeff Xu <jeffxu@chromium.org>
---
 tools/testing/selftests/mm/.gitignore |   1 +
 tools/testing/selftests/mm/Makefile   |   1 +
 tools/testing/selftests/mm/seal_elf.c | 183 ++++++++++++++++++++++++++
 3 files changed, 185 insertions(+)
 create mode 100644 tools/testing/selftests/mm/seal_elf.c

diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore
index 76474c51c786..eff280b17a6e 100644
--- a/tools/testing/selftests/mm/.gitignore
+++ b/tools/testing/selftests/mm/.gitignore
@@ -47,3 +47,4 @@ mkdirty
 va_high_addr_switch
 hugetlb_fault_after_madv
 mseal_test
+seal_elf
diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
index ba36a5c2b1fc..a0a12626cd19 100644
--- a/tools/testing/selftests/mm/Makefile
+++ b/tools/testing/selftests/mm/Makefile
@@ -60,6 +60,7 @@ TEST_GEN_FILES += mrelease_test
 TEST_GEN_FILES += mremap_dontunmap
 TEST_GEN_FILES += mremap_test
 TEST_GEN_FILES += mseal_test
+TEST_GEN_FILES += seal_elf
 TEST_GEN_FILES += on-fault-limit
 TEST_GEN_FILES += pagemap_ioctl
 TEST_GEN_FILES += thuge-gen
diff --git a/tools/testing/selftests/mm/seal_elf.c b/tools/testing/selftests/mm/seal_elf.c
new file mode 100644
index 000000000000..61a2f1c94e02
--- /dev/null
+++ b/tools/testing/selftests/mm/seal_elf.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include <sys/mman.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <stdbool.h>
+#include "../kselftest.h"
+#include <syscall.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <sys/ioctl.h>
+#include <sys/vfs.h>
+#include <sys/stat.h>
+
+/*
+ * need those definition for manually build using gcc.
+ * gcc -I ../../../../usr/include   -DDEBUG -O3  -DDEBUG -O3 seal_elf.c -o seal_elf
+ */
+#define FAIL_TEST_IF_FALSE(c) do {\
+		if (!(c)) {\
+			ksft_test_result_fail("%s, line:%d\n", __func__, __LINE__);\
+			goto test_end;\
+		} \
+	} \
+	while (0)
+
+#define SKIP_TEST_IF_FALSE(c) do {\
+		if (!(c)) {\
+			ksft_test_result_skip("%s, line:%d\n", __func__, __LINE__);\
+			goto test_end;\
+		} \
+	} \
+	while (0)
+
+
+#define TEST_END_CHECK() {\
+		ksft_test_result_pass("%s\n", __func__);\
+		return;\
+test_end:\
+		return;\
+}
+
+#ifndef u64
+#define u64 unsigned long long
+#endif
+
+/*
+ * define sys_xyx to call syscall directly.
+ */
+static int sys_mseal(void *start, size_t len)
+{
+	int sret;
+
+	errno = 0;
+	sret = syscall(__NR_mseal, start, len, 0);
+	return sret;
+}
+
+static void *sys_mmap(void *addr, unsigned long len, unsigned long prot,
+	unsigned long flags, unsigned long fd, unsigned long offset)
+{
+	void *sret;
+
+	errno = 0;
+	sret = (void *) syscall(__NR_mmap, addr, len, prot,
+		flags, fd, offset);
+	return sret;
+}
+
+inline int sys_mprotect(void *ptr, size_t size, unsigned long prot)
+{
+	int sret;
+
+	errno = 0;
+	sret = syscall(__NR_mprotect, ptr, size, prot);
+	return sret;
+}
+
+static bool seal_support(void)
+{
+	int ret;
+	void *ptr;
+	unsigned long page_size = getpagesize();
+
+	ptr = sys_mmap(NULL, page_size, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	if (ptr == (void *) -1)
+		return false;
+
+	ret = sys_mseal(ptr, page_size);
+	if (ret < 0)
+		return false;
+
+	return true;
+}
+
+const char somestr[4096] = {"READONLY"};
+
+static void test_seal_elf(void)
+{
+	int ret;
+	FILE *maps;
+	char line[512];
+	int size = 0;
+	uintptr_t  addr_start, addr_end;
+	char prot[5];
+	char filename[256];
+	unsigned long page_size = getpagesize();
+	unsigned long long ptr = (unsigned long long) somestr;
+	char *somestr2 = (char *)somestr;
+
+	/*
+	 * Modify the protection of readonly somestr
+	 */
+	if (((unsigned long long)ptr % page_size) != 0)
+		ptr = (unsigned long long)ptr & ~(page_size - 1);
+
+	ksft_print_msg("somestr = %s\n", somestr);
+	ksft_print_msg("change protection to rw\n");
+	ret = sys_mprotect((void *)ptr, page_size, PROT_READ|PROT_WRITE);
+	FAIL_TEST_IF_FALSE(!ret);
+	*somestr2 = 'A';
+	ksft_print_msg("somestr is modified to: %s\n", somestr);
+	ret = sys_mprotect((void *)ptr, page_size, PROT_READ);
+	FAIL_TEST_IF_FALSE(!ret);
+
+	maps = fopen("/proc/self/maps", "r");
+	FAIL_TEST_IF_FALSE(maps);
+
+	/*
+	 * apply sealing to elf binary
+	 */
+	while (fgets(line, sizeof(line), maps)) {
+		if (sscanf(line, "%lx-%lx %4s %*x %*x:%*x %*u %255[^\n]",
+			&addr_start, &addr_end, &prot, &filename) == 4) {
+			if (strlen(filename)) {
+				/*
+				 * seal the mapping if read only.
+				 */
+				if (strstr(prot, "r-")) {
+					ret = sys_mseal((void *)addr_start, addr_end - addr_start);
+					FAIL_TEST_IF_FALSE(!ret);
+					ksft_print_msg("sealed: %lx-%lx %s %s\n",
+						addr_start, addr_end, prot, filename);
+					if ((uintptr_t) somestr >= addr_start &&
+						(uintptr_t) somestr <= addr_end)
+						ksft_print_msg("mapping for somestr found\n");
+				}
+			}
+		}
+	}
+	fclose(maps);
+
+	ret = sys_mprotect((void *)ptr, page_size, PROT_READ | PROT_WRITE);
+	FAIL_TEST_IF_FALSE(ret < 0);
+	ksft_print_msg("somestr is sealed, mprotect is rejected\n");
+
+	TEST_END_CHECK();
+}
+
+int main(int argc, char **argv)
+{
+	bool test_seal = seal_support();
+
+	ksft_print_header();
+	ksft_print_msg("pid=%d\n", getpid());
+
+	if (!test_seal)
+		ksft_exit_skip("sealing not supported, check CONFIG_64BIT\n");
+
+	ksft_set_plan(1);
+
+	test_seal_elf();
+
+	ksft_finished();
+	return 0;
+}
-- 
2.43.0.687.g38aa6559b0-goog