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Date: Wed, 26 Jun 2019 16:49:43 +0200
From: Michal Hocko <mhocko@...nel.org>
To: Alexander Potapenko <glider@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux.com>, Kees Cook <keescook@...omium.org>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Kostya Serebryany <kcc@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Sandeep Patil <sspatil@...roid.com>,
Laura Abbott <labbott@...hat.com>,
Randy Dunlap <rdunlap@...radead.org>, Jann Horn <jannh@...gle.com>,
Mark Rutland <mark.rutland@....com>, Marco Elver <elver@...gle.com>,
Qian Cai <cai@....pw>, linux-mm@...ck.org,
linux-security-module@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v8 1/2] mm: security: introduce init_on_alloc=1 and
init_on_free=1 boot options
On Wed 26-06-19 14:19:42, Alexander Potapenko wrote:
[...]
> diff --git a/mm/dmapool.c b/mm/dmapool.c
> index 8c94c89a6f7e..fe5d33060415 100644
> --- a/mm/dmapool.c
> +++ b/mm/dmapool.c
[...]
> @@ -428,6 +428,8 @@ void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t dma)
> }
>
> offset = vaddr - page->vaddr;
> + if (want_init_on_free())
> + memset(vaddr, 0, pool->size);
any reason why this is not in DMAPOOL_DEBUG else branch? Why would you
want to both zero on free and poison on free?
> #ifdef DMAPOOL_DEBUG
> if ((dma - page->dma) != offset) {
> spin_unlock_irqrestore(&pool->lock, flags);
[...]
> @@ -1142,6 +1200,8 @@ static __always_inline bool free_pages_prepare(struct page *page,
> }
> arch_free_page(page, order);
> kernel_poison_pages(page, 1 << order, 0);
> + if (want_init_on_free())
> + kernel_init_free_pages(page, 1 << order);
same here. If you don't want to make this exclusive then you have to
zero before poisoning otherwise you are going to blow up on the poison
check, right?
> if (debug_pagealloc_enabled())
> kernel_map_pages(page, 1 << order, 0);
>
--
Michal Hocko
SUSE Labs
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