Re: [PATCH v16 04/16] mm: untag user pointers in do_pages_move

Kees Cook
2019-06-08T03:49:13Z

On Mon, Jun 03, 2019 at 06:55:06PM +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.
>
> do_pages_move() is used in the implementation of the move_pages syscall.
>
> Untag user pointers in this function.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

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

-Kees

> ---
> mm/migrate.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index f2ecc2855a12..3930bb6fa656 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1617,6 +1617,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> if (get_user(node, nodes + i))
> goto out_flush;
> addr = (unsigned long)p;
> + addr = untagged_addr(addr);
>
> err = -ENODEV;
> if (node < 0 || node >= MAX_NUMNODES)
> --
> 2.22.0.rc1.311.g5d7573a151-goog
>

--
Kees Cook