[PATCH] arm64: Clear the stack

On 06/29/2018 01:19 PM, Kees Cook wrote:

On Fri, Jun 29, 2018 at 12:05 PM, Laura Abbott [off-list ref] wrote:

quoted

Implementation of stackleak based heavily on the x86 version

Signed-off-by: Laura Abbott <redacted>
[...]
+#define current_top_of_stack() (task_stack_page(current) + THREAD_SIZE)
+#define on_thread_stack()      (on_task_stack(current, current_stack_pointer))

nit on types here. I get some warnings:

kernel/stackleak.c:55:12: warning: assignment makes integer from
pointer without a cast [-Wint-conversion]
    boundary = current_top_of_stack();
             ^
kernel/stackleak.c:65:24: warning: assignment makes integer from
pointer without a cast [-Wint-conversion]
   current->lowest_stack = current_top_of_stack() - THREAD_SIZE / 64;
                         ^

So I think this needs to be:

+#define current_top_of_stack() ((unsigned long)task_stack_page(current) + \
+                                THREAD_SIZE)

Argh, missed that in an amend, can fix for next version if there
are no other objections to this approach.

quoted

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index a535742a1c06..972ce4ca7f6a 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins

@@ -37,11 +37,14 @@ ifdef CONFIG_GCC_PLUGINS

    gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKLEAK)    += stackleak_plugin.so
    gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STACKLEAK)     += -DSTACKLEAK_PLUGIN -fplugin-arg-stackleak_plugin-track-min-size=$(CONFIG_STACKLEAK_TRACK_MIN_SIZE)
+  ifdef CONFIG_GCC_PLUGIN_STACKLEAK
+    DISABLE_STACKLEAK_PLUGIN           += -fplugin-arg-stackleak_plugin-disable
+  endif

    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
-  export SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN
+  export SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN DISABLE_STACKLEAK_PLUGIN

    ifneq ($(PLUGINCC),)
      # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.

If there is a v14, I think this hunk should be taken there, since it's
part of the common code.

Otherwise, this works for me and passes the lkdtm tests.

-Kees

Thanks,
Laura