linux-kernel - Re: [musl] Re: [PATCH v8 00/38] arm64/gcs: Provide support for GCS in userspace

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cffc9c7e-ba1c-4894-a455-8b2d687182cd@sirena.org.uk>
Date: Wed, 21 Feb 2024 00:44:43 +0000
From: Mark Brown <broonie@...nel.org>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "dalias@...c.org" <dalias@...c.org>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"suzuki.poulose@....com" <suzuki.poulose@....com>,
	"Szabolcs.Nagy@....com" <Szabolcs.Nagy@....com>,
	"musl@...ts.openwall.com" <musl@...ts.openwall.com>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
	"corbet@....net" <corbet@....net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"catalin.marinas@....com" <catalin.marinas@....com>,
	"oliver.upton@...ux.dev" <oliver.upton@...ux.dev>,
	"palmer@...belt.com" <palmer@...belt.com>,
	"debug@...osinc.com" <debug@...osinc.com>,
	"aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
	"shuah@...nel.org" <shuah@...nel.org>,
	"arnd@...db.de" <arnd@...db.de>, "maz@...nel.org" <maz@...nel.org>,
	"oleg@...hat.com" <oleg@...hat.com>,
	"fweimer@...hat.com" <fweimer@...hat.com>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"james.morse@....com" <james.morse@....com>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"will@...nel.org" <will@...nel.org>,
	"brauner@...nel.org" <brauner@...nel.org>,
	"hjl.tools@...il.com" <hjl.tools@...il.com>,
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
	"paul.walmsley@...ive.com" <paul.walmsley@...ive.com>,
	"ardb@...nel.org" <ardb@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"thiago.bauermann@...aro.org" <thiago.bauermann@...aro.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"sorear@...tmail.com" <sorear@...tmail.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [musl] Re: [PATCH v8 00/38] arm64/gcs: Provide support for GCS
 in userspace

On Wed, Feb 21, 2024 at 12:35:48AM +0000, Edgecombe, Rick P wrote:

> doing. But those threads might be using shadow stack instructions
> (INCSSP, RSTORSSP, etc). These are a collection of instructions that
> allow limited control of the SSP. When shadow stack gets disabled,
> these suddenly turn into #UD generating instructions. So any other
> threads executing those instructions when shadow stack got disabled
> would be in for a nasty surprise.

> Glibc's permissive mode (that disables shadow stack when dlopen()ing a
> DSO that doesn't support shadow stack) is quite limited because of
> this. There was a POC for working around it, but I'll stop there for
> now, to not spam you with the details. I'm not sure of arm and risc-v
> details on this specific corner, but for x86.

We have the same issue with disabling GCS causing GCS instructions to
become undefined.

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)