Re: [PATCH mm v3 04/19] kasan, arm64: unpoison stack only with CONFIG_KASAN_STACK

From: Dmitry Vyukov
Date: Mon Nov 16 2020 - 06:01:31 EST


On Fri, Nov 13, 2020 at 11:20 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote:
>
> There's a config option CONFIG_KASAN_STACK that has to be enabled for
> KASAN to use stack instrumentation and perform validity checks for
> stack variables.
>
> There's no need to unpoison stack when CONFIG_KASAN_STACK is not enabled.
> Only call kasan_unpoison_task_stack[_below]() when CONFIG_KASAN_STACK is
> enabled.
>
> Note, that CONFIG_KASAN_STACK is an option that is currently always
> defined when CONFIG_KASAN is enabled, and therefore has to be tested
> with #if instead of #ifdef.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Reviewed-by: Marco Elver <elver@xxxxxxxxxx>

Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>

> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Link: https://linux-review.googlesource.com/id/If8a891e9fe01ea543e00b576852685afec0887e3
> ---
> arch/arm64/kernel/sleep.S | 2 +-
> arch/x86/kernel/acpi/wakeup_64.S | 2 +-
> include/linux/kasan.h | 10 ++++++----
> mm/kasan/common.c | 2 ++
> 4 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index ba40d57757d6..bdadfa56b40e 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -133,7 +133,7 @@ SYM_FUNC_START(_cpu_resume)
> */
> bl cpu_do_resume
>
> -#ifdef CONFIG_KASAN
> +#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> mov x0, sp
> bl kasan_unpoison_task_stack_below
> #endif
> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index c8daa92f38dc..5d3a0b8fd379 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -112,7 +112,7 @@ SYM_FUNC_START(do_suspend_lowlevel)
> movq pt_regs_r14(%rax), %r14
> movq pt_regs_r15(%rax), %r15
>
> -#ifdef CONFIG_KASAN
> +#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> /*
> * The suspend path may have poisoned some areas deeper in the stack,
> * which we now need to unpoison.
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 0c89e6fdd29e..f2109bf0c5f9 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -76,8 +76,6 @@ static inline void kasan_disable_current(void) {}
>
> void kasan_unpoison_range(const void *address, size_t size);
>
> -void kasan_unpoison_task_stack(struct task_struct *task);
> -
> void kasan_alloc_pages(struct page *page, unsigned int order);
> void kasan_free_pages(struct page *page, unsigned int order);
>
> @@ -122,8 +120,6 @@ void kasan_restore_multi_shot(bool enabled);
>
> static inline void kasan_unpoison_range(const void *address, size_t size) {}
>
> -static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> -
> static inline void kasan_alloc_pages(struct page *page, unsigned int order) {}
> static inline void kasan_free_pages(struct page *page, unsigned int order) {}
>
> @@ -175,6 +171,12 @@ static inline size_t kasan_metadata_size(struct kmem_cache *cache) { return 0; }
>
> #endif /* CONFIG_KASAN */
>
> +#if defined(CONFIG_KASAN) && CONFIG_KASAN_STACK
> +void kasan_unpoison_task_stack(struct task_struct *task);
> +#else
> +static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> +#endif
> +
> #ifdef CONFIG_KASAN_GENERIC
>
> void kasan_cache_shrink(struct kmem_cache *cache);
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 0a420f1dbc54..7648a2452a01 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -64,6 +64,7 @@ void kasan_unpoison_range(const void *address, size_t size)
> unpoison_range(address, size);
> }
>
> +#if CONFIG_KASAN_STACK
> static void __kasan_unpoison_stack(struct task_struct *task, const void *sp)
> {
> void *base = task_stack_page(task);
> @@ -90,6 +91,7 @@ asmlinkage void kasan_unpoison_task_stack_below(const void *watermark)
>
> unpoison_range(base, watermark - base);
> }
> +#endif /* CONFIG_KASAN_STACK */
>
> void kasan_alloc_pages(struct page *page, unsigned int order)
> {
> --
> 2.29.2.299.gdc1121823c-goog
>