+++ /dev/null
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Copyright 2013-2017 by PaX Team <pageexec@freemail.hu>
- *
- * Note: the choice of the license means that the compilation process is
- * NOT 'eligible' as defined by gcc's library exception to the GPL v3,
- * but for the kernel it doesn't matter since it doesn't link against
- * any of the gcc libraries
- *
- * gcc plugin to forcibly initialize certain local variables that could
- * otherwise leak kernel stack to userland if they aren't properly initialized
- * by later code
- *
- * Homepage: https://pax.grsecurity.net/
- *
- * Options:
- * -fplugin-arg-structleak_plugin-disable
- * -fplugin-arg-structleak_plugin-verbose
- * -fplugin-arg-structleak_plugin-byref
- * -fplugin-arg-structleak_plugin-byref-all
- *
- * Usage:
- * $ # for 4.5/4.6/C based 4.7
- * $ gcc -I`gcc -print-file-name=plugin`/include -I`gcc -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o structleak_plugin.so structleak_plugin.c
- * $ # for C++ based 4.7/4.8+
- * $ g++ -I`g++ -print-file-name=plugin`/include -I`g++ -print-file-name=plugin`/include/c-family -fPIC -shared -O2 -o structleak_plugin.so structleak_plugin.c
- * $ gcc -fplugin=./structleak_plugin.so test.c -O2
- *
- * TODO: eliminate redundant initializers
- */
-
-#include "gcc-common.h"
-
-/* unused C type flag in all versions 4.5-6 */
-#define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE)
-
-__visible int plugin_is_GPL_compatible;
-
-static struct plugin_info structleak_plugin_info = {
- .version = PLUGIN_VERSION,
- .help = "disable\tdo not activate plugin\n"
- "byref\tinit structs passed by reference\n"
- "byref-all\tinit anything passed by reference\n"
- "verbose\tprint all initialized variables\n",
-};
-
-#define BYREF_STRUCT 1
-#define BYREF_ALL 2
-
-static bool verbose;
-static int byref;
-
-static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
-{
- *no_add_attrs = true;
-
- /* check for types? for now accept everything linux has to offer */
- if (TREE_CODE(*node) != FIELD_DECL)
- return NULL_TREE;
-
- *no_add_attrs = false;
- return NULL_TREE;
-}
-
-static struct attribute_spec user_attr = { };
-
-static void register_attributes(void *event_data, void *data)
-{
- user_attr.name = "user";
- user_attr.handler = handle_user_attribute;
- user_attr.affects_type_identity = true;
-
- register_attribute(&user_attr);
-}
-
-static tree get_field_type(tree field)
-{
- return strip_array_types(TREE_TYPE(field));
-}
-
-static bool is_userspace_type(tree type)
-{
- tree field;
-
- for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) {
- tree fieldtype = get_field_type(field);
- enum tree_code code = TREE_CODE(fieldtype);
-
- if (code == RECORD_TYPE || code == UNION_TYPE)
- if (is_userspace_type(fieldtype))
- return true;
-
- if (lookup_attribute("user", DECL_ATTRIBUTES(field)))
- return true;
- }
- return false;
-}
-
-static void finish_type(void *event_data, void *data)
-{
- tree type = (tree)event_data;
-
- if (type == NULL_TREE || type == error_mark_node)
- return;
-
- if (TREE_CODE(type) == ENUMERAL_TYPE)
- return;
-
- if (TYPE_USERSPACE(type))
- return;
-
- if (is_userspace_type(type))
- TYPE_USERSPACE(type) = 1;
-}
-
-static void initialize(tree var)
-{
- basic_block bb;
- gimple_stmt_iterator gsi;
- tree initializer;
- gimple init_stmt;
- tree type;
-
- /* this is the original entry bb before the forced split */
- bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
-
- /* first check if variable is already initialized, warn otherwise */
- for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
- gimple stmt = gsi_stmt(gsi);
- tree rhs1;
-
- /* we're looking for an assignment of a single rhs... */
- if (!gimple_assign_single_p(stmt))
- continue;
- rhs1 = gimple_assign_rhs1(stmt);
- /* ... of a non-clobbering expression... */
- if (TREE_CLOBBER_P(rhs1))
- continue;
- /* ... to our variable... */
- if (gimple_get_lhs(stmt) != var)
- continue;
- /* if it's an initializer then we're good */
- if (TREE_CODE(rhs1) == CONSTRUCTOR)
- return;
- }
-
- /* these aren't the 0days you're looking for */
- if (verbose)
- inform(DECL_SOURCE_LOCATION(var),
- "%s variable will be forcibly initialized",
- (byref && TREE_ADDRESSABLE(var)) ? "byref"
- : "userspace");
-
- /* build the initializer expression */
- type = TREE_TYPE(var);
- if (AGGREGATE_TYPE_P(type))
- initializer = build_constructor(type, NULL);
- else
- initializer = fold_convert(type, integer_zero_node);
-
- /* build the initializer stmt */
- init_stmt = gimple_build_assign(var, initializer);
- gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
- gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT);
- update_stmt(init_stmt);
-}
-
-static unsigned int structleak_execute(void)
-{
- basic_block bb;
- tree var;
- unsigned int i;
-
- /* split the first bb where we can put the forced initializers */
- gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
- bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
- if (!single_pred_p(bb)) {
- split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
- gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
- }
-
- /* enumerate all local variables and forcibly initialize our targets */
- FOR_EACH_LOCAL_DECL(cfun, i, var) {
- tree type = TREE_TYPE(var);
-
- gcc_assert(DECL_P(var));
- if (!auto_var_in_fn_p(var, current_function_decl))
- continue;
-
- /* only care about structure types unless byref-all */
- if (byref != BYREF_ALL && TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE)
- continue;
-
- /* if the type is of interest, examine the variable */
- if (TYPE_USERSPACE(type) ||
- (byref && TREE_ADDRESSABLE(var)))
- initialize(var);
- }
-
- return 0;
-}
-
-#define PASS_NAME structleak
-#define NO_GATE
-#define PROPERTIES_REQUIRED PROP_cfg
-#define TODO_FLAGS_FINISH TODO_verify_il | TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func | TODO_remove_unused_locals | TODO_update_ssa | TODO_ggc_collect | TODO_verify_flow
-#include "gcc-generate-gimple-pass.h"
-
-__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
-{
- int i;
- const char * const plugin_name = plugin_info->base_name;
- const int argc = plugin_info->argc;
- const struct plugin_argument * const argv = plugin_info->argv;
- bool enable = true;
-
- PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE);
-
- if (!plugin_default_version_check(version, &gcc_version)) {
- error(G_("incompatible gcc/plugin versions"));
- return 1;
- }
-
- if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
- inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
- enable = false;
- }
-
- for (i = 0; i < argc; ++i) {
- if (!strcmp(argv[i].key, "disable")) {
- enable = false;
- continue;
- }
- if (!strcmp(argv[i].key, "verbose")) {
- verbose = true;
- continue;
- }
- if (!strcmp(argv[i].key, "byref")) {
- byref = BYREF_STRUCT;
- continue;
- }
- if (!strcmp(argv[i].key, "byref-all")) {
- byref = BYREF_ALL;
- continue;
- }
- error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
- }
-
- register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info);
- if (enable) {
- register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info);
- register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL);
- }
- register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL);
-
- return 0;
-}
# SPDX-License-Identifier: GPL-2.0-only
menu "Kernel hardening options"
-config GCC_PLUGIN_STRUCTLEAK
- bool
- help
- While the kernel is built with warnings enabled for any missed
- stack variable initializations, this warning is silenced for
- anything passed by reference to another function, under the
- occasionally misguided assumption that the function will do
- the initialization. As this regularly leads to exploitable
- flaws, this plugin is available to identify and zero-initialize
- such variables, depending on the chosen level of coverage.
-
- This plugin was originally ported from grsecurity/PaX. More
- information at:
- * https://grsecurity.net/
- * https://pax.grsecurity.net/
-
menu "Memory initialization"
config CC_HAS_AUTO_VAR_INIT_PATTERN
choice
prompt "Initialize kernel stack variables at function entry"
- default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL if COMPILE_TEST && GCC_PLUGINS
default INIT_STACK_ALL_PATTERN if COMPILE_TEST && CC_HAS_AUTO_VAR_INIT_PATTERN
default INIT_STACK_ALL_ZERO if CC_HAS_AUTO_VAR_INIT_ZERO
default INIT_STACK_NONE
classes of uninitialized stack variable exploits
and information exposures.
- config GCC_PLUGIN_STRUCTLEAK_USER
- bool "zero-init structs marked for userspace (weak)"
- # Plugin can be removed once the kernel only supports GCC 12+
- depends on GCC_PLUGINS && !CC_HAS_AUTO_VAR_INIT_ZERO
- select GCC_PLUGIN_STRUCTLEAK
- help
- Zero-initialize any structures on the stack containing
- a __user attribute. This can prevent some classes of
- uninitialized stack variable exploits and information
- exposures, like CVE-2013-2141:
- https://git.kernel.org/linus/b9e146d8eb3b9eca
-
- config GCC_PLUGIN_STRUCTLEAK_BYREF
- bool "zero-init structs passed by reference (strong)"
- # Plugin can be removed once the kernel only supports GCC 12+
- depends on GCC_PLUGINS && !CC_HAS_AUTO_VAR_INIT_ZERO
- depends on !(KASAN && KASAN_STACK)
- select GCC_PLUGIN_STRUCTLEAK
- help
- Zero-initialize any structures on the stack that may
- be passed by reference and had not already been
- explicitly initialized. This can prevent most classes
- of uninitialized stack variable exploits and information
- exposures, like CVE-2017-1000410:
- https://git.kernel.org/linus/06e7e776ca4d3654
-
- As a side-effect, this keeps a lot of variables on the
- stack that can otherwise be optimized out, so combining
- this with CONFIG_KASAN_STACK can lead to a stack overflow
- and is disallowed.
-
- config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
- bool "zero-init everything passed by reference (very strong)"
- # Plugin can be removed once the kernel only supports GCC 12+
- depends on GCC_PLUGINS && !CC_HAS_AUTO_VAR_INIT_ZERO
- depends on !(KASAN && KASAN_STACK)
- select GCC_PLUGIN_STRUCTLEAK
- help
- Zero-initialize any stack variables that may be passed
- by reference and had not already been explicitly
- initialized. This is intended to eliminate all classes
- of uninitialized stack variable exploits and information
- exposures.
-
- As a side-effect, this keeps a lot of variables on the
- stack that can otherwise be optimized out, so combining
- this with CONFIG_KASAN_STACK can lead to a stack overflow
- and is disallowed.
-
config INIT_STACK_ALL_PATTERN
bool "pattern-init everything (strongest)"
depends on CC_HAS_AUTO_VAR_INIT_PATTERN
endchoice
-config GCC_PLUGIN_STRUCTLEAK_VERBOSE
- bool "Report forcefully initialized variables"
- depends on GCC_PLUGIN_STRUCTLEAK
- depends on !COMPILE_TEST # too noisy
- help
- This option will cause a warning to be printed each time the
- structleak plugin finds a variable it thinks needs to be
- initialized. Since not all existing initializers are detected
- by the plugin, this can produce false positive warnings.
-
config GCC_PLUGIN_STACKLEAK
bool "Poison kernel stack before returning from syscalls"
depends on GCC_PLUGINS
projects / thirdparty / kernel / linux.git / commitdiff
