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

[Khalid Aziz]

On 6/3/19 10:55 AM, 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 at arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl at google.com>
> ---
>  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);

Why not just "addr = (unsigned long)untagged_addr(p);"

--
Khalid