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Date: Fri, 29 Jun 2018 13:22:58 -0700
From: Laura Abbott <labbott@...hat.com>
To: Kees Cook <keescook@...omium.org>
Cc: Alexander Popov <alex.popov@...ux.com>,
Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [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 <labbott@...hat.com> wrote:
>> Implementation of stackleak based heavily on the x86 version
>>
>> Signed-off-by: Laura Abbott <labbott@...hat.com>
>> [...]
>> +#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
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