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From: Juerg Haefliger <juerg.haefliger@canonical.com>
To: Mark Rutland <mark.rutland@arm.com>, Tycho Andersen <tycho@docker.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	kernel-hardening@lists.openwall.com,
	Marco Benatto <marco.antonio.780@gmail.com>
Subject: Re: [kernel-hardening] [PATCH v5 04/10] arm64: Add __flush_tlb_one()
Date: Wed, 30 Aug 2017 07:31:25 +0200	[thread overview]
Message-ID: <2428d66f-3c31-fa73-0d6a-c16fafa99455@canonical.com> (raw)
In-Reply-To: <20170823170443.GD12567@leverpostej>


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On 08/23/2017 07:04 PM, Mark Rutland wrote:
> On Wed, Aug 23, 2017 at 10:58:42AM -0600, Tycho Andersen wrote:
>> Hi Mark,
>>
>> On Mon, Aug 14, 2017 at 05:50:47PM +0100, Mark Rutland wrote:
>>> That said, is there any reason not to use flush_tlb_kernel_range()
>>> directly?
>>
>> So it turns out that there is a difference between __flush_tlb_one() and
>> flush_tlb_kernel_range() on x86: flush_tlb_kernel_range() flushes all the TLBs
>> via on_each_cpu(), where as __flush_tlb_one() only flushes the local TLB (which
>> I think is enough here).
> 
> That sounds suspicious; I don't think that __flush_tlb_one() is
> sufficient.
> 
> If you only do local TLB maintenance, then the page is left accessible
> to other CPUs via the (stale) kernel mappings. i.e. the page isn't
> exclusively mapped by userspace.

We flush all CPUs to get rid of stale entries when a new page is
allocated to userspace that was previously allocated to the kernel.
Is that the scenario you were thinking of?

...Juerg


> Thanks,
> Mark.
> 


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  parent reply	other threads:[~2017-08-30  5:31 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-09 20:07 [PATCH v5 00/10] Add support for eXclusive Page Frame Ownership Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 01/10] mm: add MAP_HUGETLB support to vm_mmap Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 02/10] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Tycho Andersen
2017-08-14 18:51   ` Laura Abbott
2017-08-14 22:30   ` Laura Abbott
2017-08-15  3:47     ` Tycho Andersen
2017-08-15  3:51       ` Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 03/10] swiotlb: Map the buffer if it was unmapped by XPFO Tycho Andersen
2017-08-10 13:01   ` Konrad Rzeszutek Wilk
2017-08-10 16:22     ` Tycho Andersen
2017-09-20 16:19   ` Dave Hansen
2017-09-20 22:47     ` Tycho Andersen
2017-09-20 23:25       ` Dave Hansen
2017-08-09 20:07 ` [PATCH v5 04/10] arm64: Add __flush_tlb_one() Tycho Andersen
2017-08-12 11:26   ` [kernel-hardening] " Mark Rutland
2017-08-14 16:35     ` Tycho Andersen
2017-08-14 16:50       ` Mark Rutland
2017-08-14 17:01         ` Tycho Andersen
2017-08-23 16:58         ` Tycho Andersen
2017-08-23 17:04           ` Mark Rutland
2017-08-23 17:13             ` Tycho Andersen
2017-08-24 15:45               ` Mark Rutland
2017-08-29 17:24                 ` Tycho Andersen
2017-08-30  5:31             ` Juerg Haefliger [this message]
2017-08-30 16:47               ` Tycho Andersen
2017-08-31  9:43                 ` Juerg Haefliger
2017-08-31  9:47                   ` Mark Rutland
2017-08-31 21:21                     ` Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 05/10] arm64/mm: Add support for XPFO Tycho Andersen
2017-08-11 18:01   ` [kernel-hardening] " Laura Abbott
2017-08-11 20:19     ` Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled Tycho Andersen
2017-08-11 17:25   ` [kernel-hardening] " Laura Abbott
2017-08-11 21:13     ` Tycho Andersen
2017-08-11 21:52       ` Tycho Andersen
2017-08-12 11:17       ` Mark Rutland
2017-08-14 16:22         ` Tycho Andersen
2017-08-14 18:42           ` Laura Abbott
2017-08-14 20:28             ` Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 07/10] arm64/mm: Don't flush the data cache if the page is unmapped by XPFO Tycho Andersen
2017-08-12 11:57   ` [kernel-hardening] " Mark Rutland
2017-08-14 16:54     ` Mark Rutland
2017-08-14 20:27     ` Tycho Andersen
2017-08-15  9:39       ` Mark Rutland
2017-08-09 20:07 ` [PATCH v5 08/10] arm64/mm: Add support for XPFO to swiotlb Tycho Andersen
2017-08-10 13:11   ` Konrad Rzeszutek Wilk
2017-08-10 16:35     ` Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 09/10] mm: add a user_virt_to_phys symbol Tycho Andersen
2017-08-09 20:07 ` [PATCH v5 10/10] lkdtm: Add test for XPFO Tycho Andersen
2017-08-12 20:24   ` kbuild test robot
2017-08-14 16:21     ` Tycho Andersen
2017-08-12 21:05   ` kbuild test robot
2017-08-14 19:10   ` Kees Cook
2017-08-14 20:29     ` Tycho Andersen
2017-08-11 23:35 ` [kernel-hardening] [PATCH v5 00/10] Add support for eXclusive Page Frame Ownership Laura Abbott

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