Re: [PATCH v2 2/3] instrumented.h: add instrument_memcpy_before, instrument_memcpy_after
From: Marco Elver
Date: Thu Mar 21 2024 - 08:29:27 EST
On Wed, 20 Mar 2024 at 11:19, Alexander Potapenko <glider@xxxxxxxxxx> wrote:
>
> Bug detection tools based on compiler instrumentation may miss memory
> accesses in custom memcpy implementations (such as copy_mc_to_kernel).
> Provide instrumentation hooks that tell KASAN, KCSAN, and KMSAN about
> such accesses.
>
> Link: https://lore.kernel.org/all/3b7dbd88-0861-4638-b2d2-911c97a4cadf@xxxxxxxxxxxxxxxxxxx/
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Cc: Marco Elver <elver@xxxxxxxxxx>
> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
> ---
> v2: fix a copypasto in a comment spotted by Linus
> ---
> include/linux/instrumented.h | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> diff --git a/include/linux/instrumented.h b/include/linux/instrumented.h
> index 1b608e00290aa..711a1f0d1a735 100644
> --- a/include/linux/instrumented.h
> +++ b/include/linux/instrumented.h
> @@ -147,6 +147,41 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
> kmsan_unpoison_memory(to, n - left);
> }
>
> +/**
> + * instrument_memcpy_before - add instrumentation before non-instrumented memcpy
> + * @to: destination address
> + * @from: source address
> + * @n: number of bytes to copy
> + *
> + * Instrument memory accesses that happen in custom memcpy implementations. The
> + * instrumentation should be inserted before the memcpy call.
> + */
> +static __always_inline void instrument_memcpy_before(void *to, const void *from,
> + unsigned long n)
> +{
> + kasan_check_write(to, n);
> + kasan_check_read(from, n);
> + kcsan_check_write(to, n);
> + kcsan_check_read(from, n);
> +}
> +
> +/**
> + * instrument_memcpy_after - add instrumentation after non-instrumented memcpy
> + * @to: destination address
> + * @from: source address
> + * @n: number of bytes to copy
> + * @left: number of bytes not copied (if known)
> + *
> + * Instrument memory accesses that happen in custom memcpy implementations. The
> + * instrumentation should be inserted after the memcpy call.
> + */
> +static __always_inline void instrument_memcpy_after(void *to, const void *from,
> + unsigned long n,
> + unsigned long left)
> +{
> + kmsan_memmove(to, from, n - left);
> +}
> +
> /**
> * instrument_get_user() - add instrumentation to get_user()-like macros
> * @to: destination variable, may not be address-taken
> --
> 2.44.0.291.gc1ea87d7ee-goog
>