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

Andrey Konovalov
2019-06-12T11:08:50Z

On Tue, Jun 11, 2019 at 10:18 PM Khalid Aziz <khalid.aziz@oracle.com> wrote:
>
> 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@arm.com>
> > Signed-off-by: Andrey Konovalov <andreyknvl@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);"

Will do in the next version. I think I'll also merge this commit into
the "untag user pointers passed to memory syscalls" one.

>
> --
> Khalid
>