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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2017-08-06 12:06:27 +0100
committerKees Cook <keescook@chromium.org>2017-08-07 11:20:57 -0700
commitf7dd2507893cc3425d3ffc2369559619960befb0 (patch)
tree68c1f03a81c27f5ff0407b51bc2281698d86e56e /scripts
parent520eccdfe187591a51ea9ab4c1a024ae4d0f68d9 (diff)
download96b-common-f7dd2507893cc3425d3ffc2369559619960befb0.tar.gz
gcc-plugins: structleak: add option to init all vars used as byref args
In the Linux kernel, struct type variables are rarely passed by-value, and so functions that initialize such variables typically take an input reference to the variable rather than returning a value that can subsequently be used in an assignment. If the initalization function is not part of the same compilation unit, the lack of an assignment operation defeats any analysis the compiler can perform as to whether the variable may be used before having been initialized. This means we may end up passing on such variables uninitialized, resulting in potential information leaks. So extend the existing structleak GCC plugin so it will [optionally] apply to all struct type variables that have their address taken at any point, rather than only to variables of struct types that have a __user annotation. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'scripts')
-rw-r--r--scripts/Makefile.gcc-plugins1
-rw-r--r--scripts/gcc-plugins/structleak_plugin.c13
2 files changed, 12 insertions, 2 deletions
diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 2e0e2eaa397f..d1f7b0d6be66 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -27,6 +27,7 @@ ifdef CONFIG_GCC_PLUGINS
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-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL) += -fplugin-arg-structleak_plugin-byref-all
gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK) += -DSTRUCTLEAK_PLUGIN
gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT) += randomize_layout_plugin.so
diff --git a/scripts/gcc-plugins/structleak_plugin.c b/scripts/gcc-plugins/structleak_plugin.c
index fa3d7a4b26f2..3f8dd4868178 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-all
*
* Usage:
* $ # for 4.5/4.6/C based 4.7
@@ -42,6 +43,7 @@ static struct plugin_info structleak_plugin_info = {
};
static bool verbose;
+static bool byref_all;
static tree handle_user_attribute(tree *node, tree name, tree args, int flags, bool *no_add_attrs)
{
@@ -150,7 +152,9 @@ static void initialize(tree var)
/* these aren't the 0days you're looking for */
if (verbose)
inform(DECL_SOURCE_LOCATION(var),
- "userspace variable will be forcibly initialized");
+ "%s variable will be forcibly initialized",
+ (byref_all && TREE_ADDRESSABLE(var)) ? "byref"
+ : "userspace");
/* build the initializer expression */
initializer = build_constructor(TREE_TYPE(var), NULL);
@@ -190,7 +194,8 @@ static unsigned int structleak_execute(void)
continue;
/* if the type is of interest, examine the variable */
- if (TYPE_USERSPACE(type))
+ if (TYPE_USERSPACE(type) ||
+ (byref_all && TREE_ADDRESSABLE(var)))
initialize(var);
}
@@ -232,6 +237,10 @@ __visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gc
verbose = true;
continue;
}
+ if (!strcmp(argv[i].key, "byref-all")) {
+ byref_all = true;
+ continue;
+ }
error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
}