// SPDX-License-Identifier: GPL-2.0/* * Test cases for compiler-based stack variable zeroing via future * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*. */#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/init.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/string.h> /* Exfiltration buffer. */#define MAX_VAR_SIZE	128static u8 check_buf[MAX_VAR_SIZE]; /* Character array to trigger stack protector in all functions. */#define VAR_BUFFER	 32 /* Volatile mask to convince compiler to copy memory with 0xff. */static volatile u8 forced_mask = 0xff; /* Location and size tracking to validate fill and test are colocated. */static void *fill_start, *target_start;static size_t fill_size, target_size; static bool range_contains(char *haystack_start, size_t haystack_size,			   char *needle_start, size_t needle_size){	if (needle_start >= haystack_start &&	    needle_start + needle_size <= haystack_start + haystack_size)		return true;	return false;} #define DO_NOTHING_TYPE_SCALAR(var_type)	var_type#define DO_NOTHING_TYPE_STRING(var_type)	void#define DO_NOTHING_TYPE_STRUCT(var_type)	void #define DO_NOTHING_RETURN_SCALAR(ptr)		*(ptr)#define DO_NOTHING_RETURN_STRING(ptr)		/**/#define DO_NOTHING_RETURN_STRUCT(ptr)		/**/ #define DO_NOTHING_CALL_SCALAR(var, name)			\		(var) = do_nothing_ ## name(&(var))#define DO_NOTHING_CALL_STRING(var, name)			\		do_nothing_ ## name(var)#define DO_NOTHING_CALL_STRUCT(var, name)			\		do_nothing_ ## name(&(var)) #define FETCH_ARG_SCALAR(var)		&var#define FETCH_ARG_STRING(var)		var#define FETCH_ARG_STRUCT(var)		&var #define FILL_SIZE_STRING		16 #define INIT_CLONE_SCALAR		/**/#define INIT_CLONE_STRING		[FILL_SIZE_STRING]#define INIT_CLONE_STRUCT		/**/ #define INIT_SCALAR_none		/**/#define INIT_SCALAR_zero		= 0 #define INIT_STRING_none		[FILL_SIZE_STRING] /**/#define INIT_STRING_zero		[FILL_SIZE_STRING] = { } #define INIT_STRUCT_none		/**/#define INIT_STRUCT_zero		= { }#define INIT_STRUCT_static_partial	= { .two = 0, }#define INIT_STRUCT_static_all		= { .one = arg->one,		\					    .two = arg->two,		\					    .three = arg->three,	\					    .four = arg->four,		\					}#define INIT_STRUCT_dynamic_partial	= { .two = arg->two, }#define INIT_STRUCT_dynamic_all		= { .one = arg->one,		\					    .two = arg->two,		\					    .three = arg->three,	\					    .four = arg->four,		\					}#define INIT_STRUCT_runtime_partial	;				\					var.two = 0#define INIT_STRUCT_runtime_all		;				\					var.one = 0;			\					var.two = 0;			\					var.three = 0;			\					memset(&var.four, 0,		\					       sizeof(var.four)) /* * @name: unique string name for the test * @var_type: type to be tested for zeroing initialization * @which: is this a SCALAR, STRING, or STRUCT type? * @init_level: what kind of initialization is performed */#define DEFINE_TEST_DRIVER(name, var_type, which)		\/* Returns 0 on success, 1 on failure. */			\static noinline __init int test_ ## name (void)			\{								\	var_type zero INIT_CLONE_ ## which;			\	int ignored;						\	u8 sum = 0, i;						\								\	/* Notice when a new test is larger than expected. */	\	BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE);		\								\	/* Fill clone type with zero for per-field init. */	\	memset(&zero, 0x00, sizeof(zero));			\	/* Clear entire check buffer for 0xFF overlap test. */	\	memset(check_buf, 0x00, sizeof(check_buf));		\	/* Fill stack with 0xFF. */				\	ignored = leaf_ ##name((unsigned long)&ignored, 1,	\				FETCH_ARG_ ## which(zero));	\	/* Verify all bytes overwritten with 0xFF. */		\	for (sum = 0, i = 0; i < target_size; i++)		\		sum += (check_buf[i] != 0xFF);			\	if (sum) {						\		pr_err(#name ": leaf fill was not 0xFF!?\n");	\		return 1;					\	}							\	/* Clear entire check buffer for later bit tests. */	\	memset(check_buf, 0x00, sizeof(check_buf));		\	/* Extract stack-defined variable contents. */		\	ignored = leaf_ ##name((unsigned long)&ignored, 0,	\				FETCH_ARG_ ## which(zero));	\								\	/* Validate that compiler lined up fill and target. */	\	if (!range_contains(fill_start, fill_size,		\			    target_start, target_size)) {	\		pr_err(#name ": stack fill missed target!?\n");	\		pr_err(#name ": fill %zu wide\n", fill_size);	\		pr_err(#name ": target offset by %d\n",	\			(int)((ssize_t)(uintptr_t)fill_start -	\			(ssize_t)(uintptr_t)target_start));	\		return 1;					\	}							\								\	/* Look for any bytes still 0xFF in check region. */	\	for (sum = 0, i = 0; i < target_size; i++)		\		sum += (check_buf[i] == 0xFF);			\								\	if (sum == 0)						\		pr_info(#name " ok\n");				\	else							\		pr_warn(#name " FAIL (uninit bytes: %d)\n",	\			sum);					\								\	return (sum != 0);					\}#define DEFINE_TEST(name, var_type, which, init_level)		\/* no-op to force compiler into ignoring "uninitialized" vars */\static noinline __init DO_NOTHING_TYPE_ ## which(var_type)	\do_nothing_ ## name(var_type *ptr)				\{								\	/* Will always be true, but compiler doesn't know. */	\	if ((unsigned long)ptr > 0x2)				\		return DO_NOTHING_RETURN_ ## which(ptr);	\	else							\		return DO_NOTHING_RETURN_ ## which(ptr + 1);	\}								\static noinline __init int leaf_ ## name(unsigned long sp,	\					 bool fill,		\					 var_type *arg)		\{								\	char buf[VAR_BUFFER];					\	var_type var INIT_ ## which ## _ ## init_level;		\								\	target_start = &var;					\	target_size = sizeof(var);				\	/*							\	 * Keep this buffer around to make sure we've got a	\	 * stack frame of SOME kind...				\	 */							\	memset(buf, (char)(sp & 0xff), sizeof(buf));		\	/* Fill variable with 0xFF. */				\	if (fill) {						\		fill_start = &var;				\		fill_size = sizeof(var);			\		memset(fill_start,				\		       (char)((sp & 0xff) | forced_mask),	\		       fill_size);				\	}							\								\	/* Silence "never initialized" warnings. */		\	DO_NOTHING_CALL_ ## which(var, name);			\								\	/* Exfiltrate "var". */					\	memcpy(check_buf, target_start, target_size);		\								\	return (int)buf[0] | (int)buf[sizeof(buf) - 1];		\}								\DEFINE_TEST_DRIVER(name, var_type, which) /* Structure with no padding. */struct test_packed {	unsigned long one;	unsigned long two;	unsigned long three;	unsigned long four;}; /* Simple structure with padding likely to be covered by compiler. */struct test_small_hole {	size_t one;	char two;	/* 3 byte padding hole here. */	int three;	unsigned long four;}; /* Try to trigger unhandled padding in a structure. */struct test_aligned {	u32 internal1;	u64 internal2;} __aligned(64); struct test_big_hole {	u8 one;	u8 two;	u8 three;	/* 61 byte padding hole here. */	struct test_aligned four;} __aligned(64); struct test_trailing_hole {	char *one;	char *two;	char *three;	char four;	/* "sizeof(unsigned long) - 1" byte padding hole here. */}; /* Test if STRUCTLEAK is clearing structs with __user fields. */struct test_user {	u8 one;	unsigned long two;	char __user *three;	unsigned long four;}; #define DEFINE_SCALAR_TEST(name, init)				\		DEFINE_TEST(name ## _ ## init, name, SCALAR, init) #define DEFINE_SCALAR_TESTS(init)				\		DEFINE_SCALAR_TEST(u8, init);			\		DEFINE_SCALAR_TEST(u16, init);			\		DEFINE_SCALAR_TEST(u32, init);			\		DEFINE_SCALAR_TEST(u64, init);			\		DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init) #define DEFINE_STRUCT_TEST(name, init)				\		DEFINE_TEST(name ## _ ## init,			\			    struct test_ ## name, STRUCT, init) #define DEFINE_STRUCT_TESTS(init)				\		DEFINE_STRUCT_TEST(small_hole, init);		\		DEFINE_STRUCT_TEST(big_hole, init);		\		DEFINE_STRUCT_TEST(trailing_hole, init);	\		DEFINE_STRUCT_TEST(packed, init) /* These should be fully initialized all the time! */DEFINE_SCALAR_TESTS(zero);DEFINE_STRUCT_TESTS(zero);/* Static initialization: padding may be left uninitialized. */DEFINE_STRUCT_TESTS(static_partial);DEFINE_STRUCT_TESTS(static_all);/* Dynamic initialization: padding may be left uninitialized. */DEFINE_STRUCT_TESTS(dynamic_partial);DEFINE_STRUCT_TESTS(dynamic_all);/* Runtime initialization: padding may be left uninitialized. */DEFINE_STRUCT_TESTS(runtime_partial);DEFINE_STRUCT_TESTS(runtime_all);/* No initialization without compiler instrumentation. */DEFINE_SCALAR_TESTS(none);DEFINE_STRUCT_TESTS(none);DEFINE_TEST(user, struct test_user, STRUCT, none); /* * Check two uses through a variable declaration outside either path, * which was noticed as a special case in porting earlier stack init * compiler logic. */static int noinline __leaf_switch_none(int path, bool fill){	switch (path) {		uint64_t var; 	case 1:		target_start = &var;		target_size = sizeof(var);		if (fill) {			fill_start = &var;			fill_size = sizeof(var); 			memset(fill_start, forced_mask | 0x55, fill_size);		}		memcpy(check_buf, target_start, target_size);		break;	case 2:		target_start = &var;		target_size = sizeof(var);		if (fill) {			fill_start = &var;			fill_size = sizeof(var); 			memset(fill_start, forced_mask | 0xaa, fill_size);		}		memcpy(check_buf, target_start, target_size);		break;	default:		var = 5;		return var & forced_mask;	}	return 0;} static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,					      uint64_t *arg){	return __leaf_switch_none(1, fill);} static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,					      uint64_t *arg){	return __leaf_switch_none(2, fill);} DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR);DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR); static int __init test_stackinit_init(void){	unsigned int failures = 0; #define test_scalars(init)	do {				\		failures += test_u8_ ## init ();		\		failures += test_u16_ ## init ();		\		failures += test_u32_ ## init ();		\		failures += test_u64_ ## init ();		\		failures += test_char_array_ ## init ();	\	} while (0) #define test_structs(init)	do {				\		failures += test_small_hole_ ## init ();	\		failures += test_big_hole_ ## init ();		\		failures += test_trailing_hole_ ## init ();	\		failures += test_packed_ ## init ();		\	} while (0) 	/* These are explicitly initialized and should always pass. */	test_scalars(zero);	test_structs(zero);	/* Padding here appears to be accidentally always initialized? */	test_structs(dynamic_partial);	/* Padding initialization depends on compiler behaviors. */	test_structs(static_partial);	test_structs(static_all);	test_structs(dynamic_all);	test_structs(runtime_partial);	test_structs(runtime_all); 	/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */	test_scalars(none);	failures += test_switch_1_none();	failures += test_switch_2_none(); 	/* STRUCTLEAK_BYREF should cover from here down. */	test_structs(none); 	/* STRUCTLEAK will only cover this. */	failures += test_user(); 	if (failures == 0)		pr_info("all tests passed!\n");	else		pr_err("failures: %u\n", failures); 	return failures ? -EINVAL : 0;}module_init(test_stackinit_init); static void __exit test_stackinit_exit(void){ }module_exit(test_stackinit_exit); MODULE_LICENSE("GPL");