396 lines
11 KiB
C
396 lines
11 KiB
C
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// SPDX-Licenses: GPLv2
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/*
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* Test cases for compiler-based stack variable zeroing via future
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* compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/string.h>
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/* Exfiltration buffer. */
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#define MAX_VAR_SIZE 128
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static u8 check_buf[MAX_VAR_SIZE];
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/* Character array to trigger stack protector in all functions. */
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#define VAR_BUFFER 32
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/* Volatile mask to convince compiler to copy memory with 0xff. */
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static volatile u8 forced_mask = 0xff;
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/* Location and size tracking to validate fill and test are colocated. */
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static void *fill_start, *target_start;
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static size_t fill_size, target_size;
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static bool range_contains(char *haystack_start, size_t haystack_size,
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char *needle_start, size_t needle_size)
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{
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if (needle_start >= haystack_start &&
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needle_start + needle_size <= haystack_start + haystack_size)
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return true;
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return false;
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}
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#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
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#define DO_NOTHING_TYPE_STRING(var_type) void
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#define DO_NOTHING_TYPE_STRUCT(var_type) void
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#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
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#define DO_NOTHING_RETURN_STRING(ptr) /**/
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#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
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#define DO_NOTHING_CALL_SCALAR(var, name) \
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(var) = do_nothing_ ## name(&(var))
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#define DO_NOTHING_CALL_STRING(var, name) \
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do_nothing_ ## name(var)
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#define DO_NOTHING_CALL_STRUCT(var, name) \
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do_nothing_ ## name(&(var))
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#define FETCH_ARG_SCALAR(var) &var
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#define FETCH_ARG_STRING(var) var
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#define FETCH_ARG_STRUCT(var) &var
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#define FILL_SIZE_STRING 16
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#define INIT_CLONE_SCALAR /**/
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#define INIT_CLONE_STRING [FILL_SIZE_STRING]
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#define INIT_CLONE_STRUCT /**/
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#define INIT_SCALAR_none /**/
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#define INIT_SCALAR_zero = 0
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#define INIT_STRING_none [FILL_SIZE_STRING] /**/
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#define INIT_STRING_zero [FILL_SIZE_STRING] = { }
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#define INIT_STRUCT_none /**/
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#define INIT_STRUCT_zero = { }
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#define INIT_STRUCT_static_partial = { .two = 0, }
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#define INIT_STRUCT_static_all = { .one = arg->one, \
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.two = arg->two, \
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.three = arg->three, \
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.four = arg->four, \
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}
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#define INIT_STRUCT_dynamic_partial = { .two = arg->two, }
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#define INIT_STRUCT_dynamic_all = { .one = arg->one, \
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.two = arg->two, \
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.three = arg->three, \
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.four = arg->four, \
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}
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#define INIT_STRUCT_runtime_partial ; \
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var.two = 0
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#define INIT_STRUCT_runtime_all ; \
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var.one = 0; \
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var.two = 0; \
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var.three = 0; \
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memset(&var.four, 0, \
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sizeof(var.four))
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/*
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* @name: unique string name for the test
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* @var_type: type to be tested for zeroing initialization
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* @which: is this a SCALAR, STRING, or STRUCT type?
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* @init_level: what kind of initialization is performed
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* @xfail: is this test expected to fail?
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*/
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#define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
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/* Returns 0 on success, 1 on failure. */ \
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static noinline __init int test_ ## name (void) \
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{ \
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var_type zero INIT_CLONE_ ## which; \
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int ignored; \
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u8 sum = 0, i; \
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\
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/* Notice when a new test is larger than expected. */ \
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BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
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\
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/* Fill clone type with zero for per-field init. */ \
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memset(&zero, 0x00, sizeof(zero)); \
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/* Clear entire check buffer for 0xFF overlap test. */ \
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memset(check_buf, 0x00, sizeof(check_buf)); \
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/* Fill stack with 0xFF. */ \
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ignored = leaf_ ##name((unsigned long)&ignored, 1, \
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FETCH_ARG_ ## which(zero)); \
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/* Verify all bytes overwritten with 0xFF. */ \
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for (sum = 0, i = 0; i < target_size; i++) \
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sum += (check_buf[i] != 0xFF); \
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if (sum) { \
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pr_err(#name ": leaf fill was not 0xFF!?\n"); \
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return 1; \
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} \
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/* Clear entire check buffer for later bit tests. */ \
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memset(check_buf, 0x00, sizeof(check_buf)); \
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/* Extract stack-defined variable contents. */ \
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ignored = leaf_ ##name((unsigned long)&ignored, 0, \
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FETCH_ARG_ ## which(zero)); \
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\
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/* Validate that compiler lined up fill and target. */ \
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if (!range_contains(fill_start, fill_size, \
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target_start, target_size)) { \
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pr_err(#name ": stack fill missed target!?\n"); \
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pr_err(#name ": fill %zu wide\n", fill_size); \
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pr_err(#name ": target offset by %d\n", \
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(int)((ssize_t)(uintptr_t)fill_start - \
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(ssize_t)(uintptr_t)target_start)); \
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return 1; \
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} \
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\
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/* Look for any bytes still 0xFF in check region. */ \
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for (sum = 0, i = 0; i < target_size; i++) \
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sum += (check_buf[i] == 0xFF); \
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\
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if (sum == 0) { \
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pr_info(#name " ok\n"); \
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return 0; \
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} else { \
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pr_warn(#name " %sFAIL (uninit bytes: %d)\n", \
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(xfail) ? "X" : "", sum); \
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return (xfail) ? 0 : 1; \
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} \
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}
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#define DEFINE_TEST(name, var_type, which, init_level) \
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/* no-op to force compiler into ignoring "uninitialized" vars */\
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static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
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do_nothing_ ## name(var_type *ptr) \
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{ \
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/* Will always be true, but compiler doesn't know. */ \
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if ((unsigned long)ptr > 0x2) \
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return DO_NOTHING_RETURN_ ## which(ptr); \
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else \
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return DO_NOTHING_RETURN_ ## which(ptr + 1); \
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} \
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static noinline __init int leaf_ ## name(unsigned long sp, \
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bool fill, \
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var_type *arg) \
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{ \
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char buf[VAR_BUFFER]; \
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var_type var INIT_ ## which ## _ ## init_level; \
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\
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target_start = &var; \
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target_size = sizeof(var); \
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/* \
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* Keep this buffer around to make sure we've got a \
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* stack frame of SOME kind... \
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*/ \
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memset(buf, (char)(sp & 0xff), sizeof(buf)); \
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/* Fill variable with 0xFF. */ \
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if (fill) { \
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fill_start = &var; \
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fill_size = sizeof(var); \
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memset(fill_start, \
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(char)((sp & 0xff) | forced_mask), \
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fill_size); \
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} \
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\
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/* Silence "never initialized" warnings. */ \
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DO_NOTHING_CALL_ ## which(var, name); \
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\
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/* Exfiltrate "var". */ \
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memcpy(check_buf, target_start, target_size); \
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\
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return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
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} \
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DEFINE_TEST_DRIVER(name, var_type, which, 0)
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/* Structure with no padding. */
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struct test_packed {
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unsigned long one;
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unsigned long two;
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unsigned long three;
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unsigned long four;
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};
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/* Simple structure with padding likely to be covered by compiler. */
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struct test_small_hole {
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size_t one;
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char two;
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/* 3 byte padding hole here. */
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int three;
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unsigned long four;
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};
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/* Try to trigger unhandled padding in a structure. */
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struct test_aligned {
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u32 internal1;
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u64 internal2;
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} __aligned(64);
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struct test_big_hole {
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u8 one;
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u8 two;
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u8 three;
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/* 61 byte padding hole here. */
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struct test_aligned four;
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} __aligned(64);
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struct test_trailing_hole {
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char *one;
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char *two;
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char *three;
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char four;
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/* "sizeof(unsigned long) - 1" byte padding hole here. */
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};
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/* Test if STRUCTLEAK is clearing structs with __user fields. */
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struct test_user {
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u8 one;
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unsigned long two;
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char __user *three;
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unsigned long four;
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};
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#define DEFINE_SCALAR_TEST(name, init) \
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DEFINE_TEST(name ## _ ## init, name, SCALAR, init)
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#define DEFINE_SCALAR_TESTS(init) \
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DEFINE_SCALAR_TEST(u8, init); \
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DEFINE_SCALAR_TEST(u16, init); \
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DEFINE_SCALAR_TEST(u32, init); \
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DEFINE_SCALAR_TEST(u64, init); \
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DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init)
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#define DEFINE_STRUCT_TEST(name, init) \
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DEFINE_TEST(name ## _ ## init, \
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struct test_ ## name, STRUCT, init)
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#define DEFINE_STRUCT_TESTS(init) \
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DEFINE_STRUCT_TEST(small_hole, init); \
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DEFINE_STRUCT_TEST(big_hole, init); \
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DEFINE_STRUCT_TEST(trailing_hole, init); \
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DEFINE_STRUCT_TEST(packed, init)
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/* These should be fully initialized all the time! */
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DEFINE_SCALAR_TESTS(zero);
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DEFINE_STRUCT_TESTS(zero);
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/* Static initialization: padding may be left uninitialized. */
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DEFINE_STRUCT_TESTS(static_partial);
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DEFINE_STRUCT_TESTS(static_all);
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/* Dynamic initialization: padding may be left uninitialized. */
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DEFINE_STRUCT_TESTS(dynamic_partial);
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DEFINE_STRUCT_TESTS(dynamic_all);
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/* Runtime initialization: padding may be left uninitialized. */
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DEFINE_STRUCT_TESTS(runtime_partial);
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DEFINE_STRUCT_TESTS(runtime_all);
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/* No initialization without compiler instrumentation. */
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DEFINE_SCALAR_TESTS(none);
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DEFINE_STRUCT_TESTS(none);
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DEFINE_TEST(user, struct test_user, STRUCT, none);
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/*
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* Check two uses through a variable declaration outside either path,
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* which was noticed as a special case in porting earlier stack init
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* compiler logic.
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*/
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static int noinline __leaf_switch_none(int path, bool fill)
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{
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switch (path) {
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uint64_t var;
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case 1:
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target_start = &var;
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target_size = sizeof(var);
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if (fill) {
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fill_start = &var;
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fill_size = sizeof(var);
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memset(fill_start, forced_mask | 0x55, fill_size);
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}
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memcpy(check_buf, target_start, target_size);
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break;
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case 2:
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target_start = &var;
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target_size = sizeof(var);
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if (fill) {
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fill_start = &var;
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fill_size = sizeof(var);
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memset(fill_start, forced_mask | 0xaa, fill_size);
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}
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memcpy(check_buf, target_start, target_size);
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break;
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default:
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var = 5;
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return var & forced_mask;
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}
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return 0;
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}
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static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
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uint64_t *arg)
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{
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return __leaf_switch_none(1, fill);
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}
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static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
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uint64_t *arg)
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{
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return __leaf_switch_none(2, fill);
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}
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/*
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* These are expected to fail for most configurations because neither
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* GCC nor Clang have a way to perform initialization of variables in
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* non-code areas (i.e. in a switch statement before the first "case").
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* https://bugs.llvm.org/show_bug.cgi?id=44916
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*/
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DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, 1);
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DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, 1);
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static int __init test_stackinit_init(void)
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{
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unsigned int failures = 0;
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#define test_scalars(init) do { \
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failures += test_u8_ ## init (); \
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failures += test_u16_ ## init (); \
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failures += test_u32_ ## init (); \
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failures += test_u64_ ## init (); \
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failures += test_char_array_ ## init (); \
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} while (0)
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#define test_structs(init) do { \
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failures += test_small_hole_ ## init (); \
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failures += test_big_hole_ ## init (); \
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failures += test_trailing_hole_ ## init (); \
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failures += test_packed_ ## init (); \
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} while (0)
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/* These are explicitly initialized and should always pass. */
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test_scalars(zero);
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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");
|