Re: [PATCH v2 18/33] lib/string: Add KMSAN support to strlcpy() and strlcat()

[Alexander Potapenko]

On Tue, Nov 21, 2023 at 11:02 PM Ilya Leoshkevich <iii@xxxxxxxxxxxxx> wrote:
>
> Currently KMSAN does not fully propagate metadata in strlcpy() and
> strlcat(), because they are built with -ffreestanding and call
> memcpy(). In this combination memcpy() calls are not instrumented.

Is this something specific to s390?

> Fix by copying the metadata manually. Add the __STDC_HOSTED__ #ifdef in
> case the code is compiled with different flags in the future.
>
> Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
> ---
>  lib/string.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/lib/string.c b/lib/string.c
> index be26623953d2..e83c6dd77ec6 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -111,6 +111,9 @@ size_t strlcpy(char *dest, const char *src, size_t size)
>         if (size) {
>                 size_t len = (ret >= size) ? size - 1 : ret;
>                 __builtin_memcpy(dest, src, len);

On x86, I clearly see this __builtin_memcpy() being replaced with
__msan_memcpy().