diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d765d36f8737581d630a4cc84e009265680c9c3d..e718487c97c3dd2b6a09ebcc4318218fc26ca1b1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2016,6 +2016,16 @@ config TEST_OBJAGG
(or module load).
+config TEST_STACKINIT
+ tristate "Test level of stack variable initialization"
+ help
+ Test if the kernel is zero-initializing stack variables and
+ padding. Coverage is controlled by compiler flags,
+ CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
+ or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
+
+ If unsure, say N.
+
endif # RUNTIME_TESTING_MENU
config MEMTEST
diff --git a/lib/Makefile b/lib/Makefile
index c7ae0b3e4535c72b43101a3cb5d9a92a86f56726..647517940b298ccb72e732499b226ba0d044fe63 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -77,6 +77,7 @@ obj-$(CONFIG_TEST_KMOD) += test_kmod.o
obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
+obj-$(CONFIG_TEST_STACKINIT) += test_stackinit.o
obj-$(CONFIG_TEST_LIVEPATCH) += livepatch/
diff --git a/lib/test_stackinit.c b/lib/test_stackinit.c
new file mode 100644
index 0000000000000000000000000000000000000000..13115b6f2b88fdcfc56179210d1daa153db7141f
--- /dev/null
+++ b/lib/test_stackinit.c
@@ -0,0 +1,378 @@
+// SPDX-Licenses: GPLv2
+/*
+ * Test cases for compiler-based stack variable zeroing via future
+ * compiler flags or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+
+/* Exfiltration buffer. */
+#define MAX_VAR_SIZE 128
+static char check_buf[MAX_VAR_SIZE];
+
+/* Character array to trigger stack protector in all functions. */
+#define VAR_BUFFER 32
+
+/* Volatile mask to convince compiler to copy memory with 0xff. */
+static volatile u8 forced_mask = 0xff;
+
+/* Location and size tracking to validate fill and test are colocated. */
+static void *fill_start, *target_start;
+static size_t fill_size, target_size;
+
+static bool range_contains(char *haystack_start, size_t haystack_size,
+ char *needle_start, size_t needle_size)
+{
+ if (needle_start >= haystack_start &&
+ needle_start + needle_size <= haystack_start + haystack_size)
+ return true;
+ return false;
+}
+
+#define DO_NOTHING_TYPE_SCALAR(var_type) var_type
+#define DO_NOTHING_TYPE_STRING(var_type) void
+#define DO_NOTHING_TYPE_STRUCT(var_type) void
+
+#define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
+#define DO_NOTHING_RETURN_STRING(ptr) /**/
+#define DO_NOTHING_RETURN_STRUCT(ptr) /**/
+
+#define DO_NOTHING_CALL_SCALAR(var, name) \
+ (var) = do_nothing_ ## name(&(var))
+#define DO_NOTHING_CALL_STRING(var, name) \
+ do_nothing_ ## name(var)
+#define DO_NOTHING_CALL_STRUCT(var, name) \
+ do_nothing_ ## name(&(var))
+
+#define FETCH_ARG_SCALAR(var) &var
+#define FETCH_ARG_STRING(var) var
+#define FETCH_ARG_STRUCT(var) &var
+
+#define FILL_SIZE_STRING 16
+
+#define INIT_CLONE_SCALAR /**/
+#define INIT_CLONE_STRING [FILL_SIZE_STRING]
+#define INIT_CLONE_STRUCT /**/
+
+#define INIT_SCALAR_none /**/
+#define INIT_SCALAR_zero = 0
+
+#define INIT_STRING_none [FILL_SIZE_STRING] /**/
+#define INIT_STRING_zero [FILL_SIZE_STRING] = { }
+
+#define INIT_STRUCT_none /**/
+#define INIT_STRUCT_zero = { }
+#define INIT_STRUCT_static_partial = { .two = 0, }
+#define INIT_STRUCT_static_all = { .one = arg->one, \
+ .two = arg->two, \
+ .three = arg->three, \
+ .four = arg->four, \
+ }
+#define INIT_STRUCT_dynamic_partial = { .two = arg->two, }
+#define INIT_STRUCT_dynamic_all = { .one = arg->one, \
+ .two = arg->two, \
+ .three = arg->three, \
+ .four = arg->four, \
+ }
+#define INIT_STRUCT_runtime_partial ; \
+ var.two = 0
+#define INIT_STRUCT_runtime_all ; \
+ var.one = 0; \
+ var.two = 0; \
+ var.three = 0; \
+ memset(&var.four, 0, \
+ sizeof(var.four))
+
+/*
+ * @name: unique string name for the test
+ * @var_type: type to be tested for zeroing initialization
+ * @which: is this a SCALAR, STRING, or STRUCT type?
+ * @init_level: what kind of initialization is performed
+ */
+#define DEFINE_TEST_DRIVER(name, var_type, which) \
+/* Returns 0 on success, 1 on failure. */ \
+static noinline __init int test_ ## name (void) \
+{ \
+ var_type zero INIT_CLONE_ ## which; \
+ int ignored; \
+ u8 sum = 0, i; \
+ \
+ /* Notice when a new test is larger than expected. */ \
+ BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
+ \
+ /* Fill clone type with zero for per-field init. */ \
+ memset(&zero, 0x00, sizeof(zero)); \
+ /* Fill stack with 0xFF. */ \
+ ignored = leaf_ ##name((unsigned long)&ignored, 1, \
+ FETCH_ARG_ ## which(zero)); \
+ /* Clear entire check buffer for later bit tests. */ \
+ memset(check_buf, 0x00, sizeof(check_buf)); \
+ /* Extract stack-defined variable contents. */ \
+ ignored = leaf_ ##name((unsigned long)&ignored, 0, \
+ FETCH_ARG_ ## which(zero)); \
+ \
+ /* Validate that compiler lined up fill and target. */ \
+ if (!range_contains(fill_start, fill_size, \
+ target_start, target_size)) { \
+ pr_err(#name ": stack fill missed target!?\n"); \
+ pr_err(#name ": fill %zu wide\n", fill_size); \
+ pr_err(#name ": target offset by %d\n", \
+ (int)((ssize_t)(uintptr_t)fill_start - \
+ (ssize_t)(uintptr_t)target_start)); \
+ return 1; \
+ } \
+ \
+ /* Look for any set bits in the check region. */ \
+ for (i = 0; i < sizeof(check_buf); i++) \
+ sum += (check_buf[i] != 0); \
+ \
+ if (sum == 0) \
+ pr_info(#name " ok\n"); \
+ else \
+ pr_warn(#name " FAIL (uninit bytes: %d)\n", \
+ sum); \
+ \
+ return (sum != 0); \
+}
+#define DEFINE_TEST(name, var_type, which, init_level) \
+/* no-op to force compiler into ignoring "uninitialized" vars */\
+static noinline __init DO_NOTHING_TYPE_ ## which(var_type) \
+do_nothing_ ## name(var_type *ptr) \
+{ \
+ /* Will always be true, but compiler doesn't know. */ \
+ if ((unsigned long)ptr > 0x2) \
+ return DO_NOTHING_RETURN_ ## which(ptr); \
+ else \
+ return DO_NOTHING_RETURN_ ## which(ptr + 1); \
+} \
+static noinline __init int leaf_ ## name(unsigned long sp, \
+ bool fill, \
+ var_type *arg) \
+{ \
+ char buf[VAR_BUFFER]; \
+ var_type var INIT_ ## which ## _ ## init_level; \
+ \
+ target_start = &var; \
+ target_size = sizeof(var); \
+ /* \
+ * Keep this buffer around to make sure we've got a \
+ * stack frame of SOME kind... \
+ */ \
+ memset(buf, (char)(sp && 0xff), sizeof(buf)); \
+ /* Fill variable with 0xFF. */ \
+ if (fill) { \
+ fill_start = &var; \
+ fill_size = sizeof(var); \
+ memset(fill_start, \
+ (char)((sp && 0xff) | forced_mask), \
+ fill_size); \
+ } \
+ \
+ /* Silence "never initialized" warnings. */ \
+ DO_NOTHING_CALL_ ## which(var, name); \
+ \
+ /* Exfiltrate "var". */ \
+ memcpy(check_buf, target_start, target_size); \
+ \
+ return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
+} \
+DEFINE_TEST_DRIVER(name, var_type, which)
+
+/* Structure with no padding. */
+struct test_packed {
+ unsigned long one;
+ unsigned long two;
+ unsigned long three;
+ unsigned long four;
+};
+
+/* Simple structure with padding likely to be covered by compiler. */
+struct test_small_hole {
+ size_t one;
+ char two;
+ /* 3 byte padding hole here. */
+ int three;
+ unsigned long four;
+};
+
+/* Try to trigger unhandled padding in a structure. */
+struct test_aligned {
+ u32 internal1;
+ u64 internal2;
+} __aligned(64);
+
+struct test_big_hole {
+ u8 one;
+ u8 two;
+ u8 three;
+ /* 61 byte padding hole here. */
+ struct test_aligned four;
+} __aligned(64);
+
+struct test_trailing_hole {
+ char *one;
+ char *two;
+ char *three;
+ char four;
+ /* "sizeof(unsigned long) - 1" byte padding hole here. */
+};
+
+/* Test if STRUCTLEAK is clearing structs with __user fields. */
+struct test_user {
+ u8 one;
+ unsigned long two;
+ char __user *three;
+ unsigned long four;
+};
+
+#define DEFINE_SCALAR_TEST(name, init) \
+ DEFINE_TEST(name ## _ ## init, name, SCALAR, init)
+
+#define DEFINE_SCALAR_TESTS(init) \
+ DEFINE_SCALAR_TEST(u8, init); \
+ DEFINE_SCALAR_TEST(u16, init); \
+ DEFINE_SCALAR_TEST(u32, init); \
+ DEFINE_SCALAR_TEST(u64, init); \
+ DEFINE_TEST(char_array_ ## init, unsigned char, STRING, init)
+
+#define DEFINE_STRUCT_TEST(name, init) \
+ DEFINE_TEST(name ## _ ## init, \
+ struct test_ ## name, STRUCT, init)
+
+#define DEFINE_STRUCT_TESTS(init) \
+ DEFINE_STRUCT_TEST(small_hole, init); \
+ DEFINE_STRUCT_TEST(big_hole, init); \
+ DEFINE_STRUCT_TEST(trailing_hole, init); \
+ DEFINE_STRUCT_TEST(packed, init)
+
+/* These should be fully initialized all the time! */
+DEFINE_SCALAR_TESTS(zero);
+DEFINE_STRUCT_TESTS(zero);
+/* Static initialization: padding may be left uninitialized. */
+DEFINE_STRUCT_TESTS(static_partial);
+DEFINE_STRUCT_TESTS(static_all);
+/* Dynamic initialization: padding may be left uninitialized. */
+DEFINE_STRUCT_TESTS(dynamic_partial);
+DEFINE_STRUCT_TESTS(dynamic_all);
+/* Runtime initialization: padding may be left uninitialized. */
+DEFINE_STRUCT_TESTS(runtime_partial);
+DEFINE_STRUCT_TESTS(runtime_all);
+/* No initialization without compiler instrumentation. */
+DEFINE_SCALAR_TESTS(none);
+DEFINE_STRUCT_TESTS(none);
+DEFINE_TEST(user, struct test_user, STRUCT, none);
+
+/*
+ * Check two uses through a variable declaration outside either path,
+ * which was noticed as a special case in porting earlier stack init
+ * compiler logic.
+ */
+static int noinline __leaf_switch_none(int path, bool fill)
+{
+ switch (path) {
+ uint64_t var;
+
+ case 1:
+ target_start = &var;
+ target_size = sizeof(var);
+ if (fill) {
+ fill_start = &var;
+ fill_size = sizeof(var);
+
+ memset(fill_start, forced_mask | 0x55, fill_size);
+ }
+ memcpy(check_buf, target_start, target_size);
+ break;
+ case 2:
+ target_start = &var;
+ target_size = sizeof(var);
+ if (fill) {
+ fill_start = &var;
+ fill_size = sizeof(var);
+
+ memset(fill_start, forced_mask | 0xaa, fill_size);
+ }
+ memcpy(check_buf, target_start, target_size);
+ break;
+ default:
+ var = 5;
+ return var & forced_mask;
+ }
+ return 0;
+}
+
+static noinline __init int leaf_switch_1_none(unsigned long sp, bool fill,
+ uint64_t *arg)
+{
+ return __leaf_switch_none(1, fill);
+}
+
+static noinline __init int leaf_switch_2_none(unsigned long sp, bool fill,
+ uint64_t *arg)
+{
+ return __leaf_switch_none(2, fill);
+}
+
+DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR);
+DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR);
+
+static int __init test_stackinit_init(void)
+{
+ unsigned int failures = 0;
+
+#define test_scalars(init) do { \
+ failures += test_u8_ ## init (); \
+ failures += test_u16_ ## init (); \
+ failures += test_u32_ ## init (); \
+ failures += test_u64_ ## init (); \
+ failures += test_char_array_ ## init (); \
+ } while (0)
+
+#define test_structs(init) do { \
+ failures += test_small_hole_ ## init (); \
+ failures += test_big_hole_ ## init (); \
+ failures += test_trailing_hole_ ## init (); \
+ failures += test_packed_ ## init (); \
+ } while (0)
+
+ /* These are explicitly initialized and should always pass. */
+ test_scalars(zero);
+ test_structs(zero);
+ /* Padding here appears to be accidentally always initialized? */
+ test_structs(dynamic_partial);
+ /* Padding initialization depends on compiler behaviors. */
+ test_structs(static_partial);
+ test_structs(static_all);
+ test_structs(dynamic_all);
+ test_structs(runtime_partial);
+ test_structs(runtime_all);
+
+ /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
+ test_scalars(none);
+ failures += test_switch_1_none();
+ failures += test_switch_2_none();
+
+ /* STRUCTLEAK_BYREF should cover from here down. */
+ test_structs(none);
+
+ /* STRUCTLEAK will only cover this. */
+ failures += test_user();
+
+ if (failures == 0)
+ pr_info("all tests passed!\n");
+ else
+ pr_err("failures: %u\n", failures);
+
+ return failures ? -EINVAL : 0;
+}
+module_init(test_stackinit_init);
+
+static void __exit test_stackinit_exit(void)
+{ }
+module_exit(test_stackinit_exit);
+
+MODULE_LICENSE("GPL");
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 35042d96cf5da42fb485d058b0a68083b878e5be..5f7df50cfe7aa239755f31efc75fc0186592f906 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 d9fd9988ef271368034ea814148c4b2fb975c47a..74271dba4f94b5963c5f08a613d181269969868f 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -67,23 +67,59 @@ 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"
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 10292f791e992a058f3fbc38410d58a2dfa39307..e89be8f5c859da28de57b6aaf52d484dd466bd99 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);