From: Tycho Andersen <tycho@docker.com>
To: Juerg Haefliger <juerg.haefliger@canonical.com>
Cc: Yisheng Xie <xieyisheng1@huawei.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: Mon, 11 Sep 2017 09:59:36 -0700 [thread overview]
Message-ID: <20170911165936.eeqdwzir3kxkhvza@docker> (raw)
In-Reply-To: <57e95ad2-81d8-bf83-3e78-1313daa1bb80@canonical.com>
On Mon, Sep 11, 2017 at 06:03:55PM +0200, 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
> > correctly for me, but I think (?) should not because of this bug...
>
> IIRC, this is an optimization carried forward from the initial
> implementation. The assumption is that the kernel will map the user
> buffer so it's not unmapped on allocation but only on the first (and
Does the kernel always map it, though? e.g. in the case of
XPFO_READ_USER, I'm not sure where the kernel would do a kmap() of the
test's user buffer.
Tycho
> subsequent) call of kunmap. I.e.:
> - alloc -> noop
> - kmap -> noop
> - kunmap -> unmapped from the kernel
> - kmap -> mapped into the kernel
> - kunmap -> unmapped from the kernel
> and so on until:
> - free -> mapped back into the kernel
>
> I'm not sure if that make sense though since it leaves a window.
>
> ...Juerg
>
>
>
> > Tycho
> >
next prev parent reply other threads:[~2017-09-11 16:59 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 [this message]
2017-09-12 8:05 ` Yisheng Xie
2017-09-12 14:36 ` Tycho Andersen
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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