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![Jason Yan](/assets/img/avatar_default.png)
Fix the following coccicheck warning: scripts/gcc-plugins/structleak_plugin.c:177:14-17: Unneeded variable: "ret". Return "0" on line 207 Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20200418070505.10715-1-yanaijie@huawei.com
259 lines
7.3 KiB
C
259 lines
7.3 KiB
C
/*
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* Copyright 2013-2017 by PaX Team <pageexec@freemail.hu>
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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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