Re: [PATCH V2] mm: Allow userland to request that the kernel clear memory on release

From: Matthew Garrett
Date: Thu Apr 25 2019 - 16:45:57 EST

On Thu, Apr 25, 2019 at 5:44 AM Vlastimil Babka <vbabka@xxxxxxx> wrote:
> On 4/25/19 2:14 PM, Michal Hocko wrote:
> > Please cc linux-api for user visible API proposals (now done). Keep the
> > rest of the email intact for reference.
> >
> > On Wed 24-04-19 14:10:39, Matthew Garrett wrote:
> >> From: Matthew Garrett <mjg59@xxxxxxxxxx>
> >>
> >> Applications that hold secrets and wish to avoid them leaking can use
> >> mlock() to prevent the page from being pushed out to swap and
> >> MADV_DONTDUMP to prevent it from being included in core dumps. Applications
> So, do we really need a new madvise() flag and VMA flag, or can we just
> infer this page clearing from mlock+MADV_DONTDUMP being both applied?

I think the combination would probably imply that this is the
behaviour you want, but I'm a little concerned about changing the
semantics given the corner cases described earlier in the thread. If
we can figure those out in a way that won't break any existing code, I
could buy this.