diff options
| -rw-r--r-- | arch/Kconfig | 22 | ||||
| -rw-r--r-- | include/linux/compiler.h | 6 | ||||
| -rw-r--r-- | scripts/Makefile.gcc-plugins | 4 | ||||
| -rw-r--r-- | scripts/gcc-plugins/structleak_plugin.c | 246 |
4 files changed, 277 insertions, 1 deletions
diff --git a/arch/Kconfig b/arch/Kconfig index 99839c23d453..646ba0f42c5f 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -410,6 +410,28 @@ config GCC_PLUGIN_LATENT_ENTROPY * https://grsecurity.net/ * https://pax.grsecurity.net/ +config GCC_PLUGIN_STRUCTLEAK + bool "Force initialization of variables containing userspace addresses" + depends on GCC_PLUGINS + help + This plugin zero-initializes any structures that containing a + __user attribute. This can prevent some classes of information + exposures. + + This plugin was ported from grsecurity/PaX. More information at: + * https://grsecurity.net/ + * https://pax.grsecurity.net/ + +config GCC_PLUGIN_STRUCTLEAK_VERBOSE + bool "Report forcefully initialized variables" + depends on GCC_PLUGIN_STRUCTLEAK + depends on !COMPILE_TEST + 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 HAVE_CC_STACKPROTECTOR bool help diff --git a/include/linux/compiler.h b/include/linux/compiler.h index cf0fa5d86059..91c30cba984e 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -27,7 +27,11 @@ extern void __chk_user_ptr(const volatile void __user *); extern void __chk_io_ptr(const volatile void __iomem *); # define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member)) #else /* __CHECKER__ */ -# define __user +# ifdef STRUCTLEAK_PLUGIN +# define __user __attribute__((user)) +# else +# define __user +# endif # define __kernel # define __safe # define __force diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index 060d2cb373db..a084f7a511d8 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -25,6 +25,10 @@ ifdef CONFIG_GCC_PLUGINS endif endif + 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) += -DSTRUCTLEAK_PLUGIN + GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR diff --git a/scripts/gcc-plugins/structleak_plugin.c b/scripts/gcc-plugins/structleak_plugin.c new file mode 100644 index 000000000000..fa3d7a4b26f2 --- /dev/null +++ b/scripts/gcc-plugins/structleak_plugin.c @@ -0,0 +1,246 @@ +/* + * Copyright 2013-2017 by PaX Team <pageexec@freemail.hu> + * Licensed under the GPL v2 + * + * 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: http://pax.grsecurity.net/ + * + * Options: + * -fplugin-arg-structleak_plugin-disable + * -fplugin-arg-structleak_plugin-verbose + * + * 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 + * increase type coverage + */ + +#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 = "201607271510vanilla", + .help = "disable\tdo not activate plugin\n" + "verbose\tprint all initialized variables\n", +}; + +static bool verbose; + +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 = { + .name = "user", + .min_length = 0, + .max_length = 0, + .decl_required = false, + .type_required = false, + .function_type_required = false, + .handler = handle_user_attribute, +#if BUILDING_GCC_VERSION >= 4007 + .affects_type_identity = true +#endif +}; + +static void register_attributes(void *event_data, void *data) +{ + 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 BUILDING_GCC_VERSION >= 5000 + if (TREE_CODE(type) == ENUMERAL_TYPE) + return; +#endif + + 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; + + /* 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); +#if BUILDING_GCC_VERSION >= 4007 + /* ... of a non-clobbering expression... */ + if (TREE_CLOBBER_P(rhs1)) + continue; +#endif + /* ... 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), + "userspace variable will be forcibly initialized"); + + /* build the initializer expression */ + initializer = build_constructor(TREE_TYPE(var), NULL); + + /* 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; + unsigned int ret = 0; + 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 */ + if (TREE_CODE(type) != RECORD_TYPE && TREE_CODE(type) != UNION_TYPE) + continue; + + /* if the type is of interest, examine the variable */ + if (TYPE_USERSPACE(type)) + initialize(var); + } + + return ret; +} + +#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; + } + 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; +} |