From: "Michael S. Tsirkin" <mst@redhat.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>,
"Kuppuswamy,
Sathyanarayanan" <sathyanarayanan.kuppuswamy@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Richard Henderson <rth@twiddle.net>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
James E J Bottomley <James.Bottomley@hansenpartnership.com>,
Helge Deller <deller@gmx.de>,
"David S . Miller" <davem@davemloft.net>,
Arnd Bergmann <arnd@arndb.de>, Jonathan Corbet <corbet@lwn.net>,
Peter H Anvin <hpa@zytor.com>,
Dave Hansen <dave.hansen@intel.com>,
Tony Luck <tony.luck@intel.com>,
Kirill Shutemov <kirill.shutemov@linux.intel.com>,
Sean Christopherson <seanjc@google.com>,
Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
X86 ML <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux PCI <linux-pci@vger.kernel.org>,
linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org,
linux-parisc@vger.kernel.org, sparclinux@vger.kernel.org,
linux-arch <linux-arch@vger.kernel.org>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range}
Date: Sun, 29 Aug 2021 11:27:42 -0400 [thread overview]
Message-ID: <20210829112105-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <d21a2a2d-4670-ba85-ce9a-fc8ea80ef1be@linux.intel.com>
On Tue, Aug 24, 2021 at 10:20:44AM -0700, Andi Kleen wrote:
>
> > I see. Hmm. It's a bit of a random thing to do it at the map time
> > though. E.g. DMA is all handled transparently behind the DMA API.
> > Hardening is much more than just replacing map with map_shared
> > and I suspect what you will end up with is basically
> > vendors replacing map with map shared to make things work
> > for their users and washing their hands.
>
> That concept exists too. There is a separate allow list for the drivers. So
> just adding shared to a driver is not enough, until it's also added to the
> allowlist
>
> Users can of course chose to disable the allowlist, but they need to
> understand the security implications.
Right. So given that, why do we need to tweak a random API like the map?
If you just make all maps be shared then the user is in control.
Seems sensible to me.
>
> >
> > I would say an explicit flag in the driver that says "hardened"
> > and refusing to init a non hardened one would be better.
>
>
> We have that too (that's the device filtering)
>
> But the problem is that device filtering just stops the probe functions, not
> the initcalls, and lot of legacy drivers do MMIO interactions before going
> into probe. In some cases it's unavoidable because of the device doesn't
> have a separate enumeration mechanism it needs some kind of probing to even
> check for its existence And since we don't want to change all of them it's
> far safer to make the ioremap opt-in.
>
>
> -Andi
Let's be frank, even without encryption disabling most drivers -
especially weird ones that poke at hardware before probe -
is far safer than keeping them, but one loses a bunch of features.
IOW all this hardening is nice but which security/feature tradeoff
to take it a policy decision, not something kernel should do
imho.
--
MST
next prev parent reply other threads:[~2021-08-29 15:29 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-05 0:52 [PATCH v4 00/15] Add TDX Guest Support (shared-mm support) Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 01/15] x86/mm: Move force_dma_unencrypted() to common code Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 02/15] x86/tdx: Exclude Shared bit from physical_mask Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 03/15] x86/tdx: Make pages shared in ioremap() Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 04/15] x86/tdx: Add helper to do MapGPA hypercall Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 05/15] x86/tdx: Make DMA pages shared Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 06/15] x86/kvm: Use bounce buffers for TD guest Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 07/15] x86/tdx: ioapic: Add shared bit for IOAPIC base address Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 08/15] x86/tdx: Enable shared memory protected guest flags for TDX guest Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 09/15] pci: Consolidate pci_iomap* and pci_iomap*wc Kuppuswamy Sathyanarayanan
2021-08-12 19:43 ` Bjorn Helgaas
2021-08-12 22:11 ` Andi Kleen
2021-08-12 22:29 ` Kuppuswamy, Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 10/15] asm/io.h: Add ioremap_shared fallback Kuppuswamy Sathyanarayanan
2021-08-12 19:46 ` Bjorn Helgaas
2021-08-13 7:58 ` Christoph Hellwig
2021-08-05 0:52 ` [PATCH v4 11/15] pci: Add pci_iomap_shared{,_range} Kuppuswamy Sathyanarayanan
2021-08-13 8:02 ` Christoph Hellwig
2021-08-23 23:56 ` Michael S. Tsirkin
2021-08-24 0:30 ` Kuppuswamy, Sathyanarayanan
2021-08-24 1:04 ` Dan Williams
2021-08-24 2:14 ` Andi Kleen
2021-08-24 9:47 ` Michael S. Tsirkin
2021-08-24 17:20 ` Andi Kleen
2021-08-24 18:55 ` Bjorn Helgaas
2021-08-24 20:14 ` Andi Kleen
2021-08-24 20:31 ` Bjorn Helgaas
2021-08-24 20:50 ` Andi Kleen
2021-08-24 21:05 ` Dan Williams
2021-08-25 14:52 ` Bjorn Helgaas
2021-08-24 21:55 ` Rajat Jain
2021-08-29 15:27 ` Michael S. Tsirkin [this message]
2021-08-29 16:17 ` Andi Kleen
2021-08-29 22:26 ` Michael S. Tsirkin
2021-08-30 5:11 ` Andi Kleen
2021-08-30 20:59 ` Michael S. Tsirkin
2021-08-31 0:23 ` Andi Kleen
2021-09-10 9:54 ` Michael S. Tsirkin
2021-09-10 16:34 ` Andi Kleen
2021-09-11 23:54 ` Michael S. Tsirkin
2021-09-13 5:53 ` Michael S. Tsirkin
2021-09-24 22:43 ` Andi Kleen
2021-09-27 9:07 ` Michael S. Tsirkin
2021-08-24 21:56 ` Rajat Jain
2021-08-24 21:59 ` Dan Williams
2021-08-24 7:07 ` Christoph Hellwig
2021-08-24 17:04 ` Andi Kleen
2021-08-29 15:34 ` Michael S. Tsirkin
2021-08-29 16:43 ` Andi Kleen
2021-08-24 9:12 ` Michael S. Tsirkin
2021-08-05 0:52 ` [PATCH v4 12/15] pci: Mark MSI data shared Kuppuswamy Sathyanarayanan
2021-08-13 8:07 ` Christoph Hellwig
2021-08-05 0:52 ` [PATCH v4 13/15] virtio: Use shared mappings for virtio PCI devices Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 14/15] x86/tdx: Implement ioremap_shared for x86 Kuppuswamy Sathyanarayanan
2021-08-05 0:52 ` [PATCH v4 15/15] x86/tdx: Add cmdline option to force use of ioremap_shared Kuppuswamy Sathyanarayanan
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