[PATCH 3/3] lib: introduce test_meminit module

[Alexander Potapenko <glider@google.com>]

Add tests for heap and pagealloc initialization.
These can be used to check init_on_alloc and init_on_free implementations
as well as other approaches to initialization.

Expected test output in the case the kernel provides heap initialization
(e.g. when running with either init_on_alloc=1 or init_on_free=1):

  test_meminit: all 10 tests in test_pages passed
  test_meminit: all 40 tests in test_kvmalloc passed
  test_meminit: all 20 tests in test_kmemcache passed
  test_meminit: all 70 tests passed!

Signed-off-by: Alexander Potapenko <glider@google.com>
To: Kees Cook <keescook@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>
To: Christoph Lameter <cl@linux.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Sandeep Patil <sspatil@android.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: linux-mm@kvack.org
Cc: linux-security-module@vger.kernel.org
Cc: kernel-hardening@lists.openwall.com
---
 v3:
  - added example test output to the description
  - fixed a missing include spotted by kbuild test robot <lkp@intel.com>
  - added a missing MODULE_LICENSE
  - call do_kmem_cache_size() with size >= sizeof(void*) to unbreak
  debug builds
---
 lib/Kconfig.debug  |   8 ++
 lib/Makefile       |   1 +
 lib/test_meminit.c | 208 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 217 insertions(+)
 create mode 100644 lib/test_meminit.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index fdfa173651eb..036e8ef03831 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2043,6 +2043,14 @@ config TEST_STACKINIT
 
 	  If unsure, say N.
 
+config TEST_MEMINIT
+	tristate "Test level of heap/page initialization"
+	help
+	  Test if the kernel is zero-initializing heap and page allocations.
+	  This can be useful to test init_on_alloc and init_on_free features.
+
+	  If unsure, say N.
+
 endif # RUNTIME_TESTING_MENU
 
 config MEMTEST
diff --git a/lib/Makefile b/lib/Makefile
index fb7697031a79..05980c802500 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -91,6 +91,7 @@ obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
 obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
 obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
 obj-$(CONFIG_TEST_STACKINIT) += test_stackinit.o
+obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o
 
 obj-$(CONFIG_TEST_LIVEPATCH) += livepatch/
 
diff --git a/lib/test_meminit.c b/lib/test_meminit.c
new file mode 100644
index 000000000000..d46e2b8c8e8e
--- /dev/null
+++ b/lib/test_meminit.c
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test cases for SL[AOU]B/page initialization at alloc/free time.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/vmalloc.h>
+
+#define GARBAGE_INT (0x09A7BA9E)
+#define GARBAGE_BYTE (0x9E)
+
+#define REPORT_FAILURES_IN_FN() \
+	do {	\
+		if (failures)	\
+			pr_info("%s failed %d out of %d times\n",	\
+				__func__, failures, num_tests);		\
+		else		\
+			pr_info("all %d tests in %s passed\n",		\
+				num_tests, __func__);			\
+	} while (0)
+
+/* Calculate the number of uninitialized bytes in the buffer. */
+static int count_nonzero_bytes(void *ptr, size_t size)
+{
+	int i, ret = 0;
+	unsigned char *p = (unsigned char *)ptr;
+
+	for (i = 0; i < size; i++)
+		if (p[i])
+			ret++;
+	return ret;
+}
+
+static void fill_with_garbage(void *ptr, size_t size)
+{
+	unsigned int *p = (unsigned int *)ptr;
+	int i = 0;
+
+	while (size >= sizeof(*p)) {
+		p[i] = GARBAGE_INT;
+		i++;
+		size -= sizeof(*p);
+	}
+	if (size)
+		memset(&p[i], GARBAGE_BYTE, size);
+}
+
+static int __init do_alloc_pages_order(int order, int *total_failures)
+{
+	struct page *page;
+	void *buf;
+	size_t size = PAGE_SIZE << order;
+
+	page = alloc_pages(GFP_KERNEL, order);
+	buf = page_address(page);
+	fill_with_garbage(buf, size);
+	__free_pages(page, order);
+
+	page = alloc_pages(GFP_KERNEL, order);
+	buf = page_address(page);
+	if (count_nonzero_bytes(buf, size))
+		(*total_failures)++;
+	fill_with_garbage(buf, size);
+	__free_pages(page, order);
+	return 1;
+}
+
+static int __init test_pages(int *total_failures)
+{
+	int failures = 0, num_tests = 0;
+	int i;
+
+	for (i = 0; i < 10; i++)
+		num_tests += do_alloc_pages_order(i, &failures);
+
+	REPORT_FAILURES_IN_FN();
+	*total_failures += failures;
+	return num_tests;
+}
+
+static int __init do_kmalloc_size(size_t size, int *total_failures)
+{
+	void *buf;
+
+	buf = kmalloc(size, GFP_KERNEL);
+	fill_with_garbage(buf, size);
+	kfree(buf);
+
+	buf = kmalloc(size, GFP_KERNEL);
+	if (count_nonzero_bytes(buf, size))
+		(*total_failures)++;
+	fill_with_garbage(buf, size);
+	kfree(buf);
+	return 1;
+}
+
+static int __init do_vmalloc_size(size_t size, int *total_failures)
+{
+	void *buf;
+
+	buf = vmalloc(size);
+	fill_with_garbage(buf, size);
+	vfree(buf);
+
+	buf = vmalloc(size);
+	if (count_nonzero_bytes(buf, size))
+		(*total_failures)++;
+	fill_with_garbage(buf, size);
+	vfree(buf);
+	return 1;
+}
+
+static int __init test_kvmalloc(int *total_failures)
+{
+	int failures = 0, num_tests = 0;
+	int i, size;
+
+	for (i = 0; i < 20; i++) {
+		size = 1 << i;
+		num_tests += do_kmalloc_size(size, &failures);
+		num_tests += do_vmalloc_size(size, &failures);
+	}
+
+	REPORT_FAILURES_IN_FN();
+	*total_failures += failures;
+	return num_tests;
+}
+
+#define CTOR_BYTES 4
+/* Initialize the first 4 bytes of the object. */
+void some_ctor(void *obj)
+{
+	memset(obj, 'A', CTOR_BYTES);
+}
+
+static int __init do_kmem_cache_size(size_t size, bool want_ctor,
+				     int *total_failures)
+{
+	struct kmem_cache *c;
+	void *buf;
+	int iter, bytes = 0;
+	int fail = 0;
+
+	c = kmem_cache_create("test_cache", size, 1, 0,
+			      want_ctor ? some_ctor : NULL);
+	for (iter = 0; iter < 10; iter++) {
+		buf = kmem_cache_alloc(c, GFP_KERNEL);
+		if (!want_ctor || iter == 0)
+			bytes = count_nonzero_bytes(buf, size);
+		if (want_ctor) {
+			/*
+			 * Newly initialized memory must be initialized using
+			 * the constructor.
+			 */
+			if (iter == 0 && bytes < CTOR_BYTES)
+				fail = 1;
+		} else {
+			if (bytes)
+				fail = 1;
+		}
+		fill_with_garbage(buf, size);
+		kmem_cache_free(c, buf);
+	}
+	kmem_cache_destroy(c);
+
+	*total_failures += fail;
+	return 1;
+}
+
+static int __init test_kmemcache(int *total_failures)
+{
+	int failures = 0, num_tests = 0;
+	int i, size;
+
+	for (i = 0; i < 10; i++) {
+		size = 8 << i;
+		num_tests += do_kmem_cache_size(size, false, &failures);
+		num_tests += do_kmem_cache_size(size, true, &failures);
+	}
+	REPORT_FAILURES_IN_FN();
+	*total_failures += failures;
+	return num_tests;
+}
+
+static int __init test_meminit_init(void)
+{
+	int failures = 0, num_tests = 0;
+
+	num_tests += test_pages(&failures);
+	num_tests += test_kvmalloc(&failures);
+	num_tests += test_kmemcache(&failures);
+
+	if (failures == 0)
+		pr_info("all %d tests passed!\n", num_tests);
+	else
+		pr_info("failures: %d out of %d\n", failures, num_tests);
+
+	return failures ? -EINVAL : 0;
+}
+module_init(test_meminit_init);
+
+MODULE_LICENSE("GPL");
-- 
2.21.0.1020.gf2820cf01a-goog