Re: [PATCH v16 14/16] tee, arm64: untag user pointers in tee_shm_register

Kees Cook
2019-06-08T04:05:10Z

On Mon, Jun 03, 2019 at 06:55:16PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
>
> tee_shm_register()->optee_shm_unregister()->check_mem_type() uses provided
> user pointers for vma lookups (via __check_mem_type()), which can only by
> done with untagged pointers.
>
> Untag user pointers in this function.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

"tee: shm: untag user pointers in tee_shm_register"

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
> drivers/tee/tee_shm.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 49fd7312e2aa..96945f4cefb8 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -263,6 +263,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
> shm->teedev = teedev;
> shm->ctx = ctx;
> shm->id = -1;
> + addr = untagged_addr(addr);
> start = rounddown(addr, PAGE_SIZE);
> shm->offset = addr - start;
> shm->size = length;
> --
> 2.22.0.rc1.311.g5d7573a151-goog
>

--
Kees Cook