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randstruct: Enable function pointer struct detection 

This enables the automatic structure selection logic in the randstruct
GCC plugin. The selection logic randomizes all structures that contain
only function pointers, unless marked with __no_randomize_layout.

Signed-off-by: Kees Cook <keescook@chromium.org>
hifive-unleashed-5.1
Kees Cook 2017-05-05 23:56:07 -07:00
parent 3598f5d087
commit 9225331b31
2 changed files with 7 additions and 8 deletions
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12
arch/Kconfig
View File

@ -473,11 +473,13 @@ config GCC_PLUGIN_RANDSTRUCT
depends on GCC_PLUGINS
select MODVERSIONS if MODULES
help
If you say Y here, the layouts of structures explicitly
marked by __randomize_layout will be randomized at
compile-time. This can introduce the requirement of an
additional information exposure vulnerability for exploits
targeting these structure types.
If you say Y here, the layouts of structures that are entirely
function pointers (and have not been manually annotated with
__no_randomize_layout), or structures that have been explicitly
marked with __randomize_layout, will be randomized at compile-time.
This can introduce the requirement of an additional information
exposure vulnerability for exploits targeting these structure
types.
Enabling this feature will introduce some performance impact,
slightly increase memory usage, and prevent the use of forensic

3
scripts/gcc-plugins/randomize_layout_plugin.c
View File

@ -436,9 +436,6 @@ static int is_pure_ops_struct(const_tree node)
gcc_assert(TREE_CODE(node) == RECORD_TYPE || TREE_CODE(node) == UNION_TYPE);
/* XXX: Do not apply randomization to all-ftpr structs yet. */
return 0;
for (field = TYPE_FIELDS(node); field; field = TREE_CHAIN(field)) {
const_tree fieldtype = get_field_type(field);
enum tree_code code = TREE_CODE(fieldtype);