Re: [RFC PATCH v4 01/13] ptrace: Use regset_size() for dynamic regset size.

[Greentime Hu]

Oleg Nesterov <oleg@xxxxxxxxxx> æ 2020å5æ26æ éä äå10:00åéï
>
> On 05/26, Greentime Hu wrote:
> >
> > @@ -882,13 +882,18 @@ static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
> >       const struct user_regset_view *view = task_user_regset_view(task);
> >       const struct user_regset *regset = find_regset(view, type);
> >       int regset_no;
> > +     unsigned int size;
> >
> > -     if (!regset || (kiov->iov_len % regset->size) != 0)
> > +     if (!regset)
> >               return -EINVAL;
> >
> >       regset_no = regset - view->regsets;
> > -     kiov->iov_len = min(kiov->iov_len,
> > -                         (__kernel_size_t) (regset->n * regset->size));
> > +     size = regset_size(task, regset);
> > +
> > +     if ((kiov->iov_len % size) != 0)
> > +             return -EINVAL;
>
> Hmm. this doesn't look right.
>
> Before this patch we check "iov_len % regset->size", this is not the same
> as "iov_len % regset_size()".
>
> IOW, currently you can read/write, say, only the 1st register, you patch
> breaks this?
>

Hi Oleg,

Thank you. I misunderstood the meaning of regset->size
It seems I only needs to update this line, right?
- kiov->iov_len = min(kiov->iov_len,  (__kernel_size_t) (regset->n *
regset->size));
+ kiov->iov_len = min(kiov->iov_len,  (__kernel_size_t)
regset_size(task, regset));