From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "Lutomirski, Andy" <luto@kernel.org>,
"alexander.shishkin@linux.intel.com"
<alexander.shishkin@linux.intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Mehta, Sohil" <sohil.mehta@intel.com>
Subject: Re: [PATCH v3 00/12] Enable Linear Address Space Separation support
Date: Tue, 1 Aug 2023 20:38:20 +0000 [thread overview]
Message-ID: <758ebbd1851dbc5b72d4319a7afecddaf3dfe8af.camel@intel.com> (raw)
In-Reply-To: <24f0902d-3375-b0de-e985-6174c70b394c@intel.com>
On Tue, 2023-08-01 at 12:50 -0700, Sohil Mehta wrote:
> On 7/31/2023 3:36 PM, Edgecombe, Rick P wrote:
> > CET introduces this unusual instruction called WRUSS. It allows you
> > to
> > make user memory accesses while executing in the kernel. Because of
> > this special property, the CET shadow stack patches don't toggle
> > stac/clac while executing this instruction. So I think LASS will
> > need
> > it to behave more like a normal userspace access from the kernel.
> > Shadow stack is not upstream yet, so just something to keep in mind
> > for
> > the future.
> >
>
> This is a good point. We should definitely test this out to confirm.
>
> But, isn't WRUSS already defined as a user-mode access? So, in
> theory, a
> user-mode access to a user address space *should* not be blocked by
> LASS
> (even with CPL=0).
>
> Are you suggesting that we might need to do something special for
> WRUSS
> with LASS enabled?
I was, but reading the docs, I think you are right. It looks like it
will be treated like a user access as far as LASS is concerned. Thanks.
next prev parent reply other threads:[~2023-08-01 20:38 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 18:36 [PATCH v3 00/12] Enable Linear Address Space Separation support Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 01/12] x86/cpu: Enumerate the LASS feature bits Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 02/12] x86/asm: Introduce inline memcpy and memset Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 03/12] x86/alternatives: Disable LASS when patching kernel alternatives Alexander Shishkin
2023-07-31 22:41 ` Edgecombe, Rick P
2023-08-01 21:10 ` Sohil Mehta
2023-08-01 21:50 ` Edgecombe, Rick P
2023-06-09 18:36 ` [PATCH v3 04/12] x86/cpu: Enable LASS during CPU initialization Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 05/12] x86/cpu: Remove redundant comment during feature setup Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 06/12] x86/vsyscall: Reorganize the #PF emulation code Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 07/12] x86/traps: Consolidate user fixups in exc_general_protection() Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 08/12] x86/vsyscall: Add vsyscall emulation for #GP Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 09/12] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 10/12] x86/vsyscall: Document the fact that vsyscall=emulate disables LASS Alexander Shishkin
2023-06-09 18:36 ` [PATCH v3 11/12] x86/cpu: Set LASS CR4 bit as pinning sensitive Alexander Shishkin
2023-06-09 18:36 ` [RFC v3 12/12] x86/efi: Disable LASS enforcement when switching to EFI MM Alexander Shishkin
2023-07-31 18:00 ` [PATCH v3 00/12] Enable Linear Address Space Separation support Alexander Shishkin
2023-07-31 22:36 ` Edgecombe, Rick P
2023-08-01 19:50 ` Sohil Mehta
2023-08-01 20:38 ` Edgecombe, Rick P [this message]
2023-08-04 23:52 ` Edgecombe, Rick P
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