From: Tycho Andersen <tycho@docker.com>
To: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Juerg Haefliger <juerg.haefliger@canonical.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-hardening@lists.openwall.com,
Marco Benatto <marco.antonio.780@gmail.com>,
x86@kernel.org
Subject: Re: [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO)
Date: Tue, 12 Sep 2017 07:36:36 -0700 [thread overview]
Message-ID: <20170912143636.avc3ponnervs43kj@docker> (raw)
In-Reply-To: <431e2567-7600-3186-1489-93b855c395bd@huawei.com>
On Tue, Sep 12, 2017 at 04:05:22PM +0800, Yisheng Xie wrote:
>
>
> On 2017/9/12 0:03, Juerg Haefliger wrote:
> >
> >
> > On 09/11/2017 04:50 PM, Tycho Andersen wrote:
> >> Hi Yisheng,
> >>
> >> On Mon, Sep 11, 2017 at 03:24:09PM +0800, Yisheng Xie wrote:
> >>>> +void xpfo_alloc_pages(struct page *page, int order, gfp_t gfp)
> >>>> +{
> >>>> + int i, flush_tlb = 0;
> >>>> + struct xpfo *xpfo;
> >>>> +
> >>>> + if (!static_branch_unlikely(&xpfo_inited))
> >>>> + return;
> >>>> +
> >>>> + for (i = 0; i < (1 << order); i++) {
> >>>> + xpfo = lookup_xpfo(page + i);
> >>>> + if (!xpfo)
> >>>> + continue;
> >>>> +
> >>>> + WARN(test_bit(XPFO_PAGE_UNMAPPED, &xpfo->flags),
> >>>> + "xpfo: unmapped page being allocated\n");
> >>>> +
> >>>> + /* Initialize the map lock and map counter */
> >>>> + if (unlikely(!xpfo->inited)) {
> >>>> + spin_lock_init(&xpfo->maplock);
> >>>> + atomic_set(&xpfo->mapcount, 0);
> >>>> + xpfo->inited = true;
> >>>> + }
> >>>> + WARN(atomic_read(&xpfo->mapcount),
> >>>> + "xpfo: already mapped page being allocated\n");
> >>>> +
> >>>> + if ((gfp & GFP_HIGHUSER) == GFP_HIGHUSER) {
> >>>> + /*
> >>>> + * Tag the page as a user page and flush the TLB if it
> >>>> + * was previously allocated to the kernel.
> >>>> + */
> >>>> + if (!test_and_set_bit(XPFO_PAGE_USER, &xpfo->flags))
> >>>> + flush_tlb = 1;
> >>>
> >>> I'm not sure whether I am miss anything, however, when the page was previously allocated
> >>> to kernel, should we unmap the physmap (the kernel's page table) here? For we allocate
> >>> the page to user now
> >>>
> >> Yes, I think you're right. Oddly, the XPFO_READ_USER test works
>
> Hi Tycho,
> Could you share this test? I'd like to know how it works.
See the last patch in the series.
> >> correctly for me, but I think (?) should not because of this bug...
> >
> > IIRC, this is an optimization carried forward from the initial
> > implementation.
> Hi Juerg,
>
> hmm.. If below is the first version, then it seems this exist from the first version:
> https://patchwork.kernel.org/patch/8437451/
>
> > The assumption is that the kernel will map the user
> > buffer so it's not unmapped on allocation but only on the first (and
> > subsequent) call of kunmap.
>
> IMO, before a page is allocated, it is in buddy system, which means it is free
> and no other 'map' on the page except direct map. Then if the page is allocated
> to user, XPFO should unmap the direct map. otherwise the ret2dir may works at
> this window before it is freed. Or maybe I'm still missing anything.
I agree that it seems broken. I'm just not sure why the test doesn't
fail. It's certainly worth understanding.
Tycho
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next prev parent reply other threads:[~2017-09-12 14:36 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 17:35 [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Tycho Andersen
2017-09-07 17:35 ` [PATCH v6 01/11] mm: add MAP_HUGETLB support to vm_mmap Tycho Andersen
2017-09-08 7:42 ` Christoph Hellwig
2017-09-07 17:36 ` [PATCH v6 02/11] x86: always set IF before oopsing from page fault Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Tycho Andersen
2017-09-07 18:33 ` Ralph Campbell
2017-09-07 18:50 ` Tycho Andersen
2017-09-08 7:51 ` Christoph Hellwig
2017-09-08 14:58 ` Tycho Andersen
2017-09-09 15:35 ` Laura Abbott
2017-09-11 15:03 ` Tycho Andersen
2017-09-11 7:24 ` Yisheng Xie
2017-09-11 14:50 ` Tycho Andersen
2017-09-11 16:03 ` Juerg Haefliger
2017-09-11 16:59 ` Tycho Andersen
2017-09-12 8:05 ` Yisheng Xie
2017-09-12 14:36 ` Tycho Andersen [this message]
2017-09-12 18:13 ` Tycho Andersen
2017-09-14 6:15 ` Yisheng Xie
2017-09-20 23:46 ` Dave Hansen
2017-09-21 0:02 ` Tycho Andersen
2017-09-21 0:04 ` Dave Hansen
2017-09-11 18:32 ` Tycho Andersen
2017-09-11 21:54 ` Marco Benatto
2017-09-20 15:48 ` Dave Hansen
2017-09-20 22:34 ` Tycho Andersen
2017-09-20 23:21 ` Dave Hansen
2017-09-21 0:09 ` Tycho Andersen
2017-09-21 0:27 ` Dave Hansen
2017-09-21 1:37 ` Tycho Andersen
2017-11-10 1:09 ` Tycho Andersen
2017-11-13 22:20 ` Dave Hansen
2017-11-13 22:46 ` Dave Hansen
2017-11-15 0:33 ` [kernel-hardening] " Tycho Andersen
2017-11-15 0:37 ` Dave Hansen
2017-11-15 0:42 ` Tycho Andersen
2017-11-15 3:44 ` Matthew Wilcox
2017-11-15 7:00 ` Dave Hansen
2017-11-15 14:58 ` Matthew Wilcox
2017-11-15 16:20 ` [kernel-hardening] " Tycho Andersen
2017-11-15 21:34 ` Matthew Wilcox
2017-09-21 0:03 ` Dave Hansen
2017-09-21 0:28 ` Dave Hansen
2017-09-21 1:04 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 04/11] swiotlb: Map the buffer if it was unmapped by XPFO Tycho Andersen
2017-09-07 18:10 ` Christoph Hellwig
2017-09-07 18:44 ` Tycho Andersen
2017-09-08 7:13 ` Christoph Hellwig
2017-09-07 17:36 ` [PATCH v6 05/11] arm64/mm: Add support for XPFO Tycho Andersen
2017-09-08 7:53 ` Christoph Hellwig
2017-09-08 17:24 ` Tycho Andersen
2017-09-14 10:41 ` Julien Grall
2017-09-14 11:29 ` Juergen Gross
2017-09-14 18:22 ` [kernel-hardening] " Mark Rutland
2017-09-18 21:27 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 06/11] xpfo: add primitives for mapping underlying memory Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 07/11] arm64/mm, xpfo: temporarily map dcache regions Tycho Andersen
2017-09-14 18:25 ` Mark Rutland
2017-09-18 21:29 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 08/11] arm64/mm: Add support for XPFO to swiotlb Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 09/11] arm64/mm: disable section/contiguous mappings if XPFO is enabled Tycho Andersen
2017-09-09 15:38 ` Laura Abbott
2017-09-07 17:36 ` [PATCH v6 10/11] mm: add a user_virt_to_phys symbol Tycho Andersen
2017-09-08 7:55 ` Christoph Hellwig
2017-09-08 15:44 ` Kees Cook
2017-09-11 7:36 ` Christoph Hellwig
2017-09-14 18:34 ` [kernel-hardening] " Mark Rutland
2017-09-18 20:56 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 11/11] lkdtm: Add test for XPFO Tycho Andersen
2017-09-07 19:08 ` Kees Cook
2017-09-10 0:57 ` kbuild test robot
2017-09-11 10:34 ` [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Yisheng Xie
2017-09-11 15:02 ` Tycho Andersen
2017-09-12 7:07 ` Yisheng Xie
2017-09-12 7:40 ` Juerg Haefliger
2017-09-12 8:11 ` Yisheng Xie
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