[1/2] gcc-plugins: structleak: Generalize to all variable types

Message ID	20190212180441.15340-2-keescook@chromium.org (mailing list archive)
State	New, archived
Headers	show Return-Path: <kernel-hardening-return-15204-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com> Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk From: Kees Cook <keescook@chromium.org> To: linux-kernel@vger.kernel.org Cc: Kees Cook <keescook@chromium.org>, Emese Revfy <re.emese@gmail.com>, Alexander Popov <alex.popov@linux.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Laura Abbott <labbott@redhat.com>, Jann Horn <jannh@google.com>, Alexander Potapenko <glider@google.com>, kernel-hardening@lists.openwall.com Subject: [PATCH 1/2] gcc-plugins: structleak: Generalize to all variable types Date: Tue, 12 Feb 2019 10:04:40 -0800 Message-Id: <20190212180441.15340-2-keescook@chromium.org> In-Reply-To: <20190212180441.15340-1-keescook@chromium.org> References: <20190212180441.15340-1-keescook@chromium.org>
Series	gcc-plugins: structleak: Generalize to all variable types \| expand [0/2] gcc-plugins: structleak: Generalize to all variable types [1/2] gcc-plugins: structleak: Generalize to all variable types [2/2] lib: Introduce test_stackinit module

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 35042d96cf5d..5f7df50cfe7a 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -15,6 +15,8 @@ gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV) += sancov_plugin.so gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) += structleak_plugin.so gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE) \ += -fplugin-arg-structleak_plugin-verbose +gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF) \ + += -fplugin-arg-structleak_plugin-byref gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL) \ += -fplugin-arg-structleak_plugin-byref-all gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) \ diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig index d45f7f36b859..d0cc92e48f6f 100644 --- a/scripts/gcc-plugins/Kconfig +++ b/scripts/gcc-plugins/Kconfig @@ -67,27 +67,63 @@ config GCC_PLUGIN_LATENT_ENTROPY * https://pax.grsecurity.net/ config GCC_PLUGIN_STRUCTLEAK - bool "Force initialization of variables containing userspace addresses" + bool "Zero initialize stack variables" # Currently STRUCTLEAK inserts initialization out of live scope of # variables from KASAN point of view. This leads to KASAN false # positive reports. Prohibit this combination for now. depends on !KASAN_EXTRA help - This plugin zero-initializes any structures containing a - __user attribute. This can prevent some classes of information - exposures. - - This plugin was ported from grsecurity/PaX. More information at: + 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/ -config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL - bool "Force initialize all struct type variables passed by reference" +choice + prompt "Coverage" depends on GCC_PLUGIN_STRUCTLEAK - depends on !COMPILE_TEST + default GCC_PLUGIN_STRUCTLEAK_BYREF_ALL help - Zero initialize any struct type local variable that may be passed by - reference without having been initialized. + This chooses the level of coverage over classes of potentially + uninitialized variables. The selected class will be + zero-initialized before use. + + config GCC_PLUGIN_STRUCTLEAK_USER + bool "structs marked for userspace" + 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 "structs passed by reference" + 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 + + config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL + bool "anything passed by reference" + 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. + +endchoice config GCC_PLUGIN_STRUCTLEAK_VERBOSE bool "Report forcefully initialized variables" diff --git a/scripts/gcc-plugins/structleak_plugin.c b/scripts/gcc-plugins/structleak_plugin.c index 10292f791e99..e89be8f5c859 100644 --- a/scripts/gcc-plugins/structleak_plugin.c +++ b/scripts/gcc-plugins/structleak_plugin.c @@ -16,6 +16,7 @@ * Options: * -fplugin-arg-structleak_plugin-disable * -fplugin-arg-structleak_plugin-verbose + * -fplugin-arg-structleak_plugin-byref * -fplugin-arg-structleak_plugin-byref-all * * Usage: @@ -26,7 +27,6 @@ * $ gcc -fplugin=./structleak_plugin.so test.c -O2 * * TODO: eliminate redundant initializers - * increase type coverage */ #include "gcc-common.h" @@ -37,13 +37,18 @@ __visible int plugin_is_GPL_compatible; static struct plugin_info structleak_plugin_info = { - .version = "201607271510vanilla", + .version = "20190125vanilla", .help = "disable\tdo not activate plugin\n" - "verbose\tprint all initialized variables\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 bool byref_all; +static int byref; static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs) { @@ -118,6 +123,7 @@ static void initialize(tree var) 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)); @@ -148,11 +154,15 @@ static void initialize(tree var) if (verbose) inform(DECL_SOURCE_LOCATION(var), "%s variable will be forcibly initialized", - (byref_all && TREE_ADDRESSABLE(var)) ? "byref" - : "userspace"); + (byref && TREE_ADDRESSABLE(var)) ? "byref" + : "userspace"); /* build the initializer expression */ - initializer = build_constructor(TREE_TYPE(var), NULL); + 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); @@ -184,13 +194,13 @@ static unsigned int structleak_execute(void) if (!auto_var_in_fn_p(var, current_function_decl)) continue; - /* only care about structure types */ - if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) + /* 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_all && TREE_ADDRESSABLE(var))) + (byref && TREE_ADDRESSABLE(var))) initialize(var); } @@ -232,8 +242,12 @@ __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gc verbose = true; continue; } + if (!strcmp(argv[i].key, "byref")) { + byref = BYREF_STRUCT; + continue; + } if (!strcmp(argv[i].key, "byref-all")) { - byref_all = true; + byref = BYREF_ALL; continue; } error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);

[1/2] gcc-plugins: structleak: Generalize to all variable types

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