linux-kernel - Re: [PATCH 02/35] prctl: Add flag for shadow stack writeability and push/pop

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 for Android: free password hash cracker in your pocket

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

Date:   Tue, 18 Jul 2023 17:47:32 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "corbet@....net" <corbet@....net>,
        "ardb@...nel.org" <ardb@...nel.org>,
        "maz@...nel.org" <maz@...nel.org>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "Szabolcs.Nagy@....com" <Szabolcs.Nagy@....com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "james.morse@....com" <james.morse@....com>,
        "debug@...osinc.com" <debug@...osinc.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "ebiederm@...ssion.com" <ebiederm@...ssion.com>,
        "will@...nel.org" <will@...nel.org>,
        "suzuki.poulose@....com" <suzuki.poulose@....com>,
        "oliver.upton@...ux.dev" <oliver.upton@...ux.dev>,
        "broonie@...nel.org" <broonie@...nel.org>
CC:     "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "paul.walmsley@...ive.com" <paul.walmsley@...ive.com>,
        "aou@...s.berkeley.edu" <aou@...s.berkeley.edu>,
        "palmer@...belt.com" <palmer@...belt.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 02/35] prctl: Add flag for shadow stack writeability and
 push/pop

On Sun, 2023-07-16 at 22:50 +0100, Mark Brown wrote:
> On arm64 and x86 the kernel can control if there is write access to
> the
> shadow stack via specific instructions defined for the purpose,
> useful
> for things like userspace threading at the expense of some security.
> Add a flag to allow this to be selected when changing the shadow
> stack
> status.
> 
> On arm64 the kernel can separately control if userspace is able to
> pop
> and push values directly onto the shadow stack via GCS push and pop
> instructions, supporting many scenarios where userspace needs to
> write
> to the stack with less security exposure than full write access.  Add
> a
> flag to allow this to be selected when changing the shadow stack
> status.

Is this correct? I thought Szabolcs was saying pop was always
supported, but push was optional.