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]
Date:   Mon, 3 Oct 2022 22:20:20 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "jannh@...gle.com" <jannh@...gle.com>
CC:     "bsingharora@...il.com" <bsingharora@...il.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "Syromiatnikov, Eugene" <esyr@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "Yu, Yu-cheng" <yu-cheng.yu@...el.com>,
        "Eranian, Stephane" <eranian@...gle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "fweimer@...hat.com" <fweimer@...hat.com>,
        "nadav.amit@...il.com" <nadav.amit@...il.com>,
        "dethoma@...rosoft.com" <dethoma@...rosoft.com>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "bp@...en8.de" <bp@...en8.de>, "oleg@...hat.com" <oleg@...hat.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "Yang, Weijiang" <weijiang.yang@...el.com>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "jamorris@...ux.microsoft.com" <jamorris@...ux.microsoft.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "Moreira, Joao" <joao.moreira@...el.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "pavel@....cz" <pavel@....cz>,
        "mike.kravetz@...cle.com" <mike.kravetz@...cle.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "john.allen@....com" <john.allen@....com>,
        "rppt@...nel.org" <rppt@...nel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "corbet@....net" <corbet@....net>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gorcunov@...il.com" <gorcunov@...il.com>
Subject: Re: [PATCH v2 10/39] x86/mm: Introduce _PAGE_COW

On Mon, 2022-10-03 at 23:54 +0200, Jann Horn wrote:
> > > These X86_FEATURE_SHSTK checks make me uneasy. Maybe use the
> > > _PAGE_COW
> > > logic for all machines with 64-bit entries. It will get you much
> > > more
> > > coverage and more universal rules.
> > 
> > Yes, I didn't like them either at first. The reasoning originally
> > was
> > that _PAGE_COW is a bit more work and it might show up for some
> > benchmark.
> > 
> > Looking at this again though, it is just a few more operations on
> > memory that is already getting touched either way. It must be a
> > very
> > tiny amount of impact if any. I'm fine removing them. Having just
> > one
> > set of logic around this would make it easier to reason about.
> > 
> > Dave, any thoughts on this?
> 
> But the rules wouldn't actually be universal - you'd still have to
> look at X86_FEATURE_SHSTK in code that wants to figure out whether a
> PTE is shadow stack (on a newer CPU) or readonly dirty (on an older
> CPU that can set dirty bits on non-present PTEs), right?

Good point. It still would need a check in pte_shstk() or pte_write(),
so pte_write() doesn't think CPU created Write=0,Dirty=1 memory is
writable. Which then percolates to most of the other checks anyway.

Powered by blists - more mailing lists