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259 lines
7.3 KiB
259 lines
7.3 KiB
/* |
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* Copyright 2013-2017 by PaX Team <[email protected]> |
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* Licensed under the GPL v2 |
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* |
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* Note: the choice of the license means that the compilation process is |
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* NOT 'eligible' as defined by gcc's library exception to the GPL v3, |
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* but for the kernel it doesn't matter since it doesn't link against |
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* any of the gcc libraries |
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* |
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* gcc plugin to forcibly initialize certain local variables that could |
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* otherwise leak kernel stack to userland if they aren't properly initialized |
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* by later code |
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* |
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* Homepage: https://pax.grsecurity.net/ |
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* |
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* Options: |
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* -fplugin-arg-structleak_plugin-disable |
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* -fplugin-arg-structleak_plugin-verbose |
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* -fplugin-arg-structleak_plugin-byref |
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* -fplugin-arg-structleak_plugin-byref-all |
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* |
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* Usage: |
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* $ # for 4.5/4.6/C based 4.7 |
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* $ 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 |
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* $ # for C++ based 4.7/4.8+ |
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* $ 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 |
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* $ gcc -fplugin=./structleak_plugin.so test.c -O2 |
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* |
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* TODO: eliminate redundant initializers |
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*/ |
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#include "gcc-common.h" |
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/* unused C type flag in all versions 4.5-6 */ |
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#define TYPE_USERSPACE(TYPE) TYPE_LANG_FLAG_5(TYPE) |
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__visible int plugin_is_GPL_compatible; |
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static struct plugin_info structleak_plugin_info = { |
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.version = "20190125vanilla", |
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.help = "disable\tdo not activate plugin\n" |
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"byref\tinit structs passed by reference\n" |
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"byref-all\tinit anything passed by reference\n" |
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"verbose\tprint all initialized variables\n", |
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}; |
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#define BYREF_STRUCT 1 |
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#define BYREF_ALL 2 |
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static bool verbose; |
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static int byref; |
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static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs) |
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{ |
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*no_add_attrs = true; |
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/* check for types? for now accept everything linux has to offer */ |
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if (TREE_CODE(*node) != FIELD_DECL) |
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return NULL_TREE; |
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*no_add_attrs = false; |
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return NULL_TREE; |
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} |
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static struct attribute_spec user_attr = { }; |
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static void register_attributes(void *event_data, void *data) |
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{ |
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user_attr.name = "user"; |
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user_attr.handler = handle_user_attribute; |
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user_attr.affects_type_identity = true; |
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register_attribute(&user_attr); |
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} |
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static tree get_field_type(tree field) |
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{ |
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return strip_array_types(TREE_TYPE(field)); |
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} |
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static bool is_userspace_type(tree type) |
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{ |
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tree field; |
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for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) { |
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tree fieldtype = get_field_type(field); |
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enum tree_code code = TREE_CODE(fieldtype); |
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if (code == RECORD_TYPE || code == UNION_TYPE) |
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if (is_userspace_type(fieldtype)) |
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return true; |
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if (lookup_attribute("user", DECL_ATTRIBUTES(field))) |
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return true; |
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} |
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return false; |
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} |
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static void finish_type(void *event_data, void *data) |
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{ |
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tree type = (tree)event_data; |
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if (type == NULL_TREE || type == error_mark_node) |
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return; |
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#if BUILDING_GCC_VERSION >= 5000 |
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if (TREE_CODE(type) == ENUMERAL_TYPE) |
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return; |
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#endif |
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if (TYPE_USERSPACE(type)) |
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return; |
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if (is_userspace_type(type)) |
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TYPE_USERSPACE(type) = 1; |
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} |
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static void initialize(tree var) |
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{ |
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basic_block bb; |
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gimple_stmt_iterator gsi; |
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tree initializer; |
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gimple init_stmt; |
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tree type; |
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/* this is the original entry bb before the forced split */ |
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bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); |
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/* first check if variable is already initialized, warn otherwise */ |
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for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) { |
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gimple stmt = gsi_stmt(gsi); |
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tree rhs1; |
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/* we're looking for an assignment of a single rhs... */ |
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if (!gimple_assign_single_p(stmt)) |
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continue; |
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rhs1 = gimple_assign_rhs1(stmt); |
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/* ... of a non-clobbering expression... */ |
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if (TREE_CLOBBER_P(rhs1)) |
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continue; |
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/* ... to our variable... */ |
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if (gimple_get_lhs(stmt) != var) |
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continue; |
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/* if it's an initializer then we're good */ |
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if (TREE_CODE(rhs1) == CONSTRUCTOR) |
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return; |
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} |
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/* these aren't the 0days you're looking for */ |
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if (verbose) |
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inform(DECL_SOURCE_LOCATION(var), |
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"%s variable will be forcibly initialized", |
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(byref && TREE_ADDRESSABLE(var)) ? "byref" |
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: "userspace"); |
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/* build the initializer expression */ |
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type = TREE_TYPE(var); |
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if (AGGREGATE_TYPE_P(type)) |
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initializer = build_constructor(type, NULL); |
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else |
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initializer = fold_convert(type, integer_zero_node); |
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/* build the initializer stmt */ |
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init_stmt = gimple_build_assign(var, initializer); |
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gsi = gsi_after_labels(single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
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gsi_insert_before(&gsi, init_stmt, GSI_NEW_STMT); |
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update_stmt(init_stmt); |
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} |
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static unsigned int structleak_execute(void) |
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{ |
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basic_block bb; |
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tree var; |
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unsigned int i; |
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/* split the first bb where we can put the forced initializers */ |
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gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
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bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); |
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if (!single_pred_p(bb)) { |
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split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
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gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun))); |
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} |
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/* enumerate all local variables and forcibly initialize our targets */ |
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FOR_EACH_LOCAL_DECL(cfun, i, var) { |
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tree type = TREE_TYPE(var); |
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gcc_assert(DECL_P(var)); |
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if (!auto_var_in_fn_p(var, current_function_decl)) |
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continue; |
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/* only care about structure types unless byref-all */ |
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if (byref != BYREF_ALL && TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) |
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continue; |
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/* if the type is of interest, examine the variable */ |
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if (TYPE_USERSPACE(type) || |
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(byref && TREE_ADDRESSABLE(var))) |
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initialize(var); |
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} |
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return 0; |
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} |
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#define PASS_NAME structleak |
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#define NO_GATE |
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#define PROPERTIES_REQUIRED PROP_cfg |
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#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 |
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#include "gcc-generate-gimple-pass.h" |
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__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) |
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{ |
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int i; |
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const char * const plugin_name = plugin_info->base_name; |
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const int argc = plugin_info->argc; |
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const struct plugin_argument * const argv = plugin_info->argv; |
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bool enable = true; |
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PASS_INFO(structleak, "early_optimizations", 1, PASS_POS_INSERT_BEFORE); |
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if (!plugin_default_version_check(version, &gcc_version)) { |
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error(G_("incompatible gcc/plugin versions")); |
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return 1; |
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} |
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if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) { |
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inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name); |
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enable = false; |
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} |
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for (i = 0; i < argc; ++i) { |
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if (!strcmp(argv[i].key, "disable")) { |
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enable = false; |
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continue; |
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} |
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if (!strcmp(argv[i].key, "verbose")) { |
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verbose = true; |
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continue; |
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} |
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if (!strcmp(argv[i].key, "byref")) { |
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byref = BYREF_STRUCT; |
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continue; |
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} |
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if (!strcmp(argv[i].key, "byref-all")) { |
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byref = BYREF_ALL; |
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continue; |
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} |
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error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key); |
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} |
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register_callback(plugin_name, PLUGIN_INFO, NULL, &structleak_plugin_info); |
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if (enable) { |
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register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &structleak_pass_info); |
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register_callback(plugin_name, PLUGIN_FINISH_TYPE, finish_type, NULL); |
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} |
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register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); |
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return 0; |
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}
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