On Fri, 18 Aug 2017 12:28:29 -0400 Rik van Riel <[email protected]> wrote:
> On Thu, 2017-08-17 at 15:50 -0700, Andrew Morton wrote: > > On Tue, 15 Aug 2017 22:18:19 -0400 Rik van Riel <[email protected]> > > wrote: > > > > > > > --- a/mm/madvise.c > > > > > +++ b/mm/madvise.c > > > > > @@ -80,6 +80,17 @@ static long madvise_behavior(struct > > > > > vm_area_struct *vma, > > > > > __ } > > > > > __ new_flags &= ~VM_DONTCOPY; > > > > > __ break; > > > > > + case MADV_WIPEONFORK: > > > > > + /* MADV_WIPEONFORK is only supported on > > > > > anonymous > > > > > memory. */ > > > > > + if (vma->vm_file || vma->vm_flags & VM_SHARED) > > > > > { > > > > > + error = -EINVAL; > > > > > + goto out; > > > > > + } > > > > > + new_flags |= VM_WIPEONFORK; > > > > > + break; > > > > > + case MADV_KEEPONFORK: > > > > > + new_flags &= ~VM_WIPEONFORK; > > > > > + break; > > > > > __ case MADV_DONTDUMP: > > > > > __ new_flags |= VM_DONTDUMP; > > > > > __ break; > > > > > > > > It seems odd to permit MADV_KEEPONFORK against other-than-anon > > > > vmas? > > > > > > Given that the only way to set VM_WIPEONFORK is through > > > MADV_WIPEONFORK, calling MADV_KEEPONFORK on an > > > other-than-anon vma would be equivalent to a noop. > > > > > > If new_flags == vma->vm_flags, madvise_behavior() will > > > immediately exit. > > > > Yes, but calling MADV_WIPEONFORK against an other-than-anon vma is > > presumably a userspace bug.____A bug which will probably result in > > userspace having WIPEONFORK memory which it didn't want.____The kernel > > can trivially tell userspace that it has this bug so why not do so? > > Uh, what? > Braino. I meant MADV_KEEPONFORK. Calling MADV_KEEPONFORK against an other-than-anon vma is a presumptive userspace bug and the kernel should report that.
