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-rw-r--r--scripts/gcc-plugins/Kconfig62
-rw-r--r--scripts/gcc-plugins/structleak_plugin.c36
2 files changed, 72 insertions, 26 deletions
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index d45f7f36b859..74271dba4f94 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -67,27 +67,59 @@ config GCC_PLUGIN_LATENT_ENTROPY
* https://pax.grsecurity.net/
config GCC_PLUGIN_STRUCTLEAK
- bool "Force initialization of variables containing userspace addresses"
- # 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
+ 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 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);