Re: [PATCH -mm 1/1] ptrace: PTRACE_GETFDPIC: fix the unsafe usage

[Oleg Nesterov <oleg@redhat.com>]

On 05/25, David Howells wrote:
>
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > > Like PEEKTEXT and POKETEXT?
> >
> > They use access_process_vm().
>
> Which needs to get the mm:
>
> 	int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
> 	{
> 		struct vm_area_struct *vma;
> 		struct mm_struct *mm;
>
> 		if (addr + len < addr)
> 			return 0;
>
> 		mm = get_task_mm(tsk);

Yes sure,

But I do not think it makes any sense to change the signature of
access_process_vm() as well, it has a lot of callers. And it is
complex, it does get_user_pages(). Compared to that get_task_mm()
inside of access_process_vm() is nothing.

Oleg.