Re: [PATCH] arm64: Clear the stack

[Laura Abbott]

On 06/29/2018 01:19 PM, Kees Cook wrote:
> On Fri, Jun 29, 2018 at 12:05 PM, Laura Abbott <labbott@xxxxxxxxxx> wrote:
> > Implementation of stackleak based heavily on the x86 version
> >
> > Signed-off-by: Laura Abbott <labbott@xxxxxxxxxx>
> > [...]
> > +#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.

> > 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