Updates to the gcc-plugins:

- infrastructure updates (gcc-common.h)
 - introduce structleak plugin for forced initialization of some structures
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 Version: GnuPG v1
 Comment: Kees Cook <kees@outflux.net>
 
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Merge tag 'gcc-plugins-v4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull gcc-plugins updates from Kees Cook:
 "This includes infrastructure updates and the structleak plugin, which
  performs forced initialization of certain structures to avoid possible
  information exposures to userspace.

  Summary:

   - infrastructure updates (gcc-common.h)

   - introduce structleak plugin for forced initialization of some
     structures"

* tag 'gcc-plugins-v4.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  gcc-plugins: Add structleak for more stack initialization
  gcc-plugins: consolidate on PASS_INFO macro
  gcc-plugins: add PASS_INFO and build_const_char_string()

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

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

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

scripts/gcc-plugins/cyc_complexity_plugin.c

@@ -52,12 +52,8 @@ static unsigned int cyc_complexity_execute(void)
 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 {
 	const char * const plugin_name = plugin_info->base_name;
-	struct register_pass_info cyc_complexity_pass_info;
 
-	cyc_complexity_pass_info.pass				= make_cyc_complexity_pass();
-	cyc_complexity_pass_info.reference_pass_name		= "ssa";
-	cyc_complexity_pass_info.ref_pass_instance_number	= 1;
-	cyc_complexity_pass_info.pos_op				= PASS_POS_INSERT_AFTER;
+	PASS_INFO(cyc_complexity, "ssa", 1, PASS_POS_INSERT_AFTER);
 
 	if (!plugin_default_version_check(version, &gcc_version)) {
 		error(G_("incompatible gcc/plugin versions"));

scripts/gcc-plugins/gcc-common.h

@@ -26,6 +26,9 @@
 #include "except.h"
 #include "function.h"
 #include "toplev.h"
+#if BUILDING_GCC_VERSION >= 5000
+#include "expr.h"
+#endif
 #include "basic-block.h"
 #include "intl.h"
 #include "ggc.h"
@@ -80,6 +83,9 @@
 #include "diagnostic.h"
 #include "tree-dump.h"
 #include "tree-pass.h"
+#if BUILDING_GCC_VERSION >= 4009
+#include "pass_manager.h"
+#endif
 #include "predict.h"
 #include "ipa-utils.h"
 
@@ -119,20 +125,17 @@
 #include "builtins.h"
 #endif
 
-/* #include "expr.h" where are you... */
-extern rtx emit_move_insn(rtx x, rtx y);
-
 /* missing from basic_block.h... */
-extern void debug_dominance_info(enum cdi_direction dir);
-extern void debug_dominance_tree(enum cdi_direction dir, basic_block root);
+void debug_dominance_info(enum cdi_direction dir);
+void debug_dominance_tree(enum cdi_direction dir, basic_block root);
 
 #if BUILDING_GCC_VERSION == 4006
-extern void debug_gimple_stmt(gimple);
-extern void debug_gimple_seq(gimple_seq);
-extern void print_gimple_seq(FILE *, gimple_seq, int, int);
-extern void print_gimple_stmt(FILE *, gimple, int, int);
-extern void print_gimple_expr(FILE *, gimple, int, int);
-extern void dump_gimple_stmt(pretty_printer *, gimple, int, int);
+void debug_gimple_stmt(gimple);
+void debug_gimple_seq(gimple_seq);
+void print_gimple_seq(FILE *, gimple_seq, int, int);
+void print_gimple_stmt(FILE *, gimple, int, int);
+void print_gimple_expr(FILE *, gimple, int, int);
+void dump_gimple_stmt(pretty_printer *, gimple, int, int);
 #endif
 
 #define __unused __attribute__((__unused__))
@@ -146,6 +149,29 @@ extern void dump_gimple_stmt(pretty_printer *, gimple, int, int);
 /* should come from c-tree.h if only it were installed for gcc 4.5... */
 #define C_TYPE_FIELDS_READONLY(TYPE) TREE_LANG_FLAG_1(TYPE)
 
+static inline tree build_const_char_string(int len, const char *str)
+{
+	tree cstr, elem, index, type;
+
+	cstr = build_string(len, str);
+	elem = build_type_variant(char_type_node, 1, 0);
+	index = build_index_type(size_int(len - 1));
+	type = build_array_type(elem, index);
+	TREE_TYPE(cstr) = type;
+	TREE_CONSTANT(cstr) = 1;
+	TREE_READONLY(cstr) = 1;
+	TREE_STATIC(cstr) = 1;
+	return cstr;
+}
+
+#define PASS_INFO(NAME, REF, ID, POS)		\
+struct register_pass_info NAME##_pass_info = {	\
+	.pass = make_##NAME##_pass(),		\
+	.reference_pass_name = REF,		\
+	.ref_pass_instance_number = ID,		\
+	.pos_op = POS,				\
+}
+
 #if BUILDING_GCC_VERSION == 4005
 #define FOR_EACH_LOCAL_DECL(FUN, I, D)			\
 	for (tree vars = (FUN)->local_decls, (I) = 0;	\
@@ -527,6 +553,8 @@ static inline const greturn *as_a_const_greturn(const_gimple stmt)
 #define section_name_prefix LTO_SECTION_NAME_PREFIX
 #define fatal_error(loc, gmsgid, ...) fatal_error((gmsgid), __VA_ARGS__)
 
+rtx emit_move_insn(rtx x, rtx y);
+
 typedef struct rtx_def rtx_insn;
 
 static inline const char *get_decl_section_name(const_tree decl)
@@ -643,6 +671,11 @@ static inline const greturn *as_a_const_greturn(const_gimple stmt)
 #define NODE_DECL(node) (node)->decl
 #define cgraph_node_name(node) (node)->name()
 #define NODE_IMPLICIT_ALIAS(node) (node)->cpp_implicit_alias
+
+static inline opt_pass *get_pass_for_id(int id)
+{
+	return g->get_passes()->get_pass_for_id(id);
+}
 #endif
 
 #if BUILDING_GCC_VERSION >= 5000 && BUILDING_GCC_VERSION < 6000

scripts/gcc-plugins/latent_entropy_plugin.c

@@ -592,12 +592,6 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
 	const struct plugin_argument * const argv = plugin_info->argv;
 	int i;
 
-	struct register_pass_info latent_entropy_pass_info;
-
-	latent_entropy_pass_info.pass		= make_latent_entropy_pass();
-	latent_entropy_pass_info.reference_pass_name		= "optimized";
-	latent_entropy_pass_info.ref_pass_instance_number	= 1;
-	latent_entropy_pass_info.pos_op		= PASS_POS_INSERT_BEFORE;
 	static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
 		{
 			.base = &latent_entropy_decl,
@@ -609,6 +603,8 @@ __visible int plugin_init(struct plugin_name_args *plugin_info,
 		LAST_GGC_ROOT_TAB
 	};
 
+	PASS_INFO(latent_entropy, "optimized", 1, PASS_POS_INSERT_BEFORE);
+
 	if (!plugin_default_version_check(version, &gcc_version)) {
 		error(G_("incompatible gcc/plugin versions"));
 		return 1;

scripts/gcc-plugins/sancov_plugin.c

@@ -89,7 +89,6 @@ static void sancov_start_unit(void __unused *gcc_data, void __unused *user_data)
 __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
 {
 	int i;
-	struct register_pass_info sancov_plugin_pass_info;
 	const char * const plugin_name = plugin_info->base_name;
 	const int argc = plugin_info->argc;
 	const struct plugin_argument * const argv = plugin_info->argv;
@@ -107,14 +106,11 @@ __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gc
 	};
 
 	/* BBs can be split afterwards?? */
-	sancov_plugin_pass_info.pass				= make_sancov_pass();
 #if BUILDING_GCC_VERSION >= 4009
-	sancov_plugin_pass_info.reference_pass_name		= "asan";
+	PASS_INFO(sancov, "asan", 0, PASS_POS_INSERT_BEFORE);
 #else
-	sancov_plugin_pass_info.reference_pass_name		= "nrv";
+	PASS_INFO(sancov, "nrv", 1, PASS_POS_INSERT_BEFORE);
 #endif
-	sancov_plugin_pass_info.ref_pass_instance_number	= 0;
-	sancov_plugin_pass_info.pos_op				= PASS_POS_INSERT_BEFORE;
 
 	if (!plugin_default_version_check(version, &gcc_version)) {
 		error(G_("incompatible gcc/plugin versions"));

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;
+}