gcc-plugins: structleak: add option to init all vars used as byref args
In the Linux kernel, struct type variables are rarely passed by-value, and so functions that initialize such variables typically take an input reference to the variable rather than returning a value that can subsequently be used in an assignment. If the initalization function is not part of the same compilation unit, the lack of an assignment operation defeats any analysis the compiler can perform as to whether the variable may be used before having been initialized. This means we may end up passing on such variables uninitialized, resulting in potential information leaks. So extend the existing structleak GCC plugin so it will [optionally] apply to all struct type variables that have their address taken at any point, rather than only to variables of struct types that have a __user annotation. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Kees Cook <keescook@chromium.org>
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@ -458,6 +458,13 @@ config GCC_PLUGIN_STRUCTLEAK
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* https://grsecurity.net/
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* https://grsecurity.net/
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* https://pax.grsecurity.net/
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* https://pax.grsecurity.net/
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config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
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bool "Force initialize all struct type variables passed by reference"
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depends on GCC_PLUGIN_STRUCTLEAK
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help
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Zero initialize any struct type local variable that may be passed by
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reference without having been initialized.
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config GCC_PLUGIN_STRUCTLEAK_VERBOSE
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config GCC_PLUGIN_STRUCTLEAK_VERBOSE
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bool "Report forcefully initialized variables"
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bool "Report forcefully initialized variables"
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depends on GCC_PLUGIN_STRUCTLEAK
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depends on GCC_PLUGIN_STRUCTLEAK
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@ -27,6 +27,7 @@ ifdef CONFIG_GCC_PLUGINS
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gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) += structleak_plugin.so
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gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) += structleak_plugin.so
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gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE) += -fplugin-arg-structleak_plugin-verbose
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gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE) += -fplugin-arg-structleak_plugin-verbose
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gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL) += -fplugin-arg-structleak_plugin-byref-all
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gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) += -DSTRUCTLEAK_PLUGIN
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gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) += -DSTRUCTLEAK_PLUGIN
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gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += randomize_layout_plugin.so
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gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += randomize_layout_plugin.so
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@ -16,6 +16,7 @@
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* Options:
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* Options:
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* -fplugin-arg-structleak_plugin-disable
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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-verbose
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* -fplugin-arg-structleak_plugin-byref-all
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*
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*
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* Usage:
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* Usage:
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* $ # for 4.5/4.6/C based 4.7
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* $ # for 4.5/4.6/C based 4.7
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@ -42,6 +43,7 @@ static struct plugin_info structleak_plugin_info = {
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};
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};
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static bool verbose;
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static bool verbose;
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static bool byref_all;
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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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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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{
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@ -150,7 +152,9 @@ static void initialize(tree var)
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/* these aren't the 0days you're looking for */
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/* these aren't the 0days you're looking for */
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if (verbose)
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if (verbose)
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inform(DECL_SOURCE_LOCATION(var),
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inform(DECL_SOURCE_LOCATION(var),
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"userspace variable will be forcibly initialized");
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"%s variable will be forcibly initialized",
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(byref_all && TREE_ADDRESSABLE(var)) ? "byref"
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: "userspace");
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/* build the initializer expression */
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/* build the initializer expression */
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initializer = build_constructor(TREE_TYPE(var), NULL);
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initializer = build_constructor(TREE_TYPE(var), NULL);
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@ -190,7 +194,8 @@ static unsigned int structleak_execute(void)
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continue;
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continue;
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/* if the type is of interest, examine the variable */
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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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if (TYPE_USERSPACE(type) ||
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(byref_all && TREE_ADDRESSABLE(var)))
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initialize(var);
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initialize(var);
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}
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}
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@ -232,6 +237,10 @@ __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gc
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verbose = true;
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verbose = true;
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continue;
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continue;
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}
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}
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if (!strcmp(argv[i].key, "byref-all")) {
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byref_all = true;
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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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error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
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}
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}
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