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395 lines
11 KiB
395 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0 |
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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); |
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/* Padding here appears to be accidentally always initialized? */ |
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test_structs(dynamic_partial); |
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/* Padding initialization depends on compiler behaviors. */ |
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test_structs(static_partial); |
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test_structs(static_all); |
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test_structs(dynamic_all); |
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test_structs(runtime_partial); |
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test_structs(runtime_all); |
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/* STRUCTLEAK_BYREF_ALL should cover everything from here down. */ |
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test_scalars(none); |
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failures += test_switch_1_none(); |
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failures += test_switch_2_none(); |
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/* STRUCTLEAK_BYREF should cover from here down. */ |
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test_structs(none); |
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/* STRUCTLEAK will only cover this. */ |
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failures += test_user(); |
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if (failures == 0) |
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pr_info("all tests passed!\n"); |
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else |
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pr_err("failures: %u\n", failures); |
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return failures ? -EINVAL : 0; |
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} |
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module_init(test_stackinit_init); |
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static void __exit test_stackinit_exit(void) |
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{ } |
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module_exit(test_stackinit_exit); |
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MODULE_LICENSE("GPL");
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