Re: [PATCH v7 1/2] mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options

[Alexander Potapenko <glider@google.com>]

On Fri, Jun 21, 2019 at 5:12 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Fri 21-06-19 16:10:19, Alexander Potapenko wrote:
> > On Fri, Jun 21, 2019 at 10:57 AM Alexander Potapenko <glider@google.com> wrote:
> [...]
> > > > > diff --git a/mm/dmapool.c b/mm/dmapool.c
> > > > > index 8c94c89a6f7e..e164012d3491 100644
> > > > > --- a/mm/dmapool.c
> > > > > +++ b/mm/dmapool.c
> > > > > @@ -378,7 +378,7 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
> > > > >  #endif
> > > > >       spin_unlock_irqrestore(&pool->lock, flags);
> > > > >
> > > > > -     if (mem_flags & __GFP_ZERO)
> > > > > +     if (want_init_on_alloc(mem_flags))
> > > > >               memset(retval, 0, pool->size);
> > > > >
> > > > >       return retval;
> > > >
> > > > Don't you miss dma_pool_free and want_init_on_free?
> > > Agreed.
> > > I'll fix this and add tests for DMA pools as well.
> > This doesn't seem to be easy though. One needs a real DMA-capable
> > device to allocate using DMA pools.
> > On the other hand, what happens to a DMA pool when it's destroyed,
> > isn't it wiped by pagealloc?
>
> Yes it should be returned to the page allocator AFAIR. But it is when we
> are returning an object to the pool when you want to wipe the data, no?
My concern was that dma allocation is something orthogonal to heap and
page allocator.
I also don't know how many other allocators are left overboard, e.g.
we don't do anything to lib/genalloc.c yet.

> Why cannot you do it along the already existing poisoning?
I can sure keep these bits.
Any idea how the correct behavior of dma_pool_alloc/free can be tested?
> --
> Michal Hocko
> SUSE Labs



-- 
Alexander Potapenko
Software Engineer

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