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-rw-r--r--lib/test_stackinit.c389
1 files changed, 389 insertions, 0 deletions
diff --git a/lib/test_stackinit.c b/lib/test_stackinit.c
new file mode 100644
index 000000000..16b1d3a3a
--- /dev/null
+++ b/lib/test_stackinit.c
@@ -0,0 +1,389 @@
+// 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 128
+static 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 = 0, \
+ .two = 0, \
+ .three = 0, \
+ .four = 0, \
+ }
+#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; \
+ var.four = 0
+
+/*
+ * @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
+ * @xfail: is this test expected to fail?
+ */
+#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
+/* 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"); \
+ return 0; \
+ } else { \
+ pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \
+ (xfail) ? "X" : "", sum); \
+ return (xfail) ? 0 : 1; \
+ } \
+}
+#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, 0)
+
+/* 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;
+};
+
+/* Trigger unhandled padding in a structure. */
+struct test_big_hole {
+ u8 one;
+ u8 two;
+ u8 three;
+ /* 61 byte padding hole here. */
+ u8 four __aligned(64);
+} __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);
+}
+
+/*
+ * These are expected to fail for most configurations because neither
+ * GCC nor Clang have a way to perform initialization of variables in
+ * non-code areas (i.e. in a switch statement before the first "case").
+ * https://bugs.llvm.org/show_bug.cgi?id=44916
+ */
+DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, 1);
+DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, 1);
+
+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");
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