Re: [PATCH bpf-next v3 09/17] mm: kasan: Declare kasan_unpoison_task_stack_below in kasan.h

Andrey Konovalov
2023-09-16T16:25:05Z

On Wed, Sep 13, 2023 at 1:32 AM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> We require access to this kasan helper in BPF code in the next patch
> where we have to unpoison the task stack when we unwind and reset the
> stack frame from bpf_throw, and it never really unpoisons the poisoned
> stack slots on entry when compiler instrumentation is generated by
> CONFIG_KASAN_STACK and inline instrumentation is supported.
>
> Also, remove the declaration from mm/kasan/kasan.h as we put it in the
> header file kasan.h.
>
> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Suggested-by: Andrey Konovalov <andreyknvl@gmail.com>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---
> include/linux/kasan.h | 2 ++
> mm/kasan/kasan.h | 1 -
> 2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 819b6bc8ac08..7a463f814db2 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -283,8 +283,10 @@ static inline bool kasan_check_byte(const void *address)
>
> #if defined(CONFIG_KASAN) && defined(CONFIG_KASAN_STACK)
> void kasan_unpoison_task_stack(struct task_struct *task);
> +asmlinkage void kasan_unpoison_task_stack_below(const void *watermark);
> #else
> static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
> +static inline void kasan_unpoison_task_stack_below(const void *watermark) {}
> #endif
>
> #ifdef CONFIG_KASAN_GENERIC
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 2e973b36fe07..5eefe202bb8f 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -558,7 +558,6 @@ void kasan_restore_multi_shot(bool enabled);
> * code. Declared here to avoid warnings about missing declarations.
> */
>
> -asmlinkage void kasan_unpoison_task_stack_below(const void *watermark);
> void __asan_register_globals(void *globals, ssize_t size);
> void __asan_unregister_globals(void *globals, ssize_t size);
> void __asan_handle_no_return(void);
> --
> 2.41.0
>

Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>

Thanks!