linux-kernel - Re: [PATCH v11 25/25] x86/cet/shstk: Add arch

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: <ab1a3344-60f4-9b9d-81d4-e6538fdcafcf@intel.com>
Date:   Wed, 9 Sep 2020 15:59:27 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Yu, Yu-cheng" <yu-cheng.yu@...el.com>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Dave Martin <Dave.Martin@....com>, "H.J. Lu" <hjl.tools@...il.com>,
        Florian Weimer <fweimer@...hat.com>, X86 ML <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Jann Horn <jannh@...gle.com>, Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Weijiang Yang <weijiang.yang@...el.com>
Subject: Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for
 shadow stack

On 9/9/20 3:08 PM, Yu, Yu-cheng wrote:
> After looking at this more, I found the changes are more similar to
> mprotect() than madvise().  We are going to change an anonymous mapping
> to a read-only mapping, and add the VM_SHSTK flag to it.  Would an
> x86-specific mprotect(PROT_SHSTK) make more sense?
> 
> One alternative would be requiring a read-only mapping for
> madvise(MADV_SHSTK).  But that is inconvenient for the application.

Why?  It's just:

	mmap()/malloc();
	mprotect(PROT_READ);
	madvise(MADV_SHSTK);

vs.

	mmap()/malloc();
	mprotect(PROT_SHSTK);

I'm not sure a single syscall counts as inconvenient.

I don't quite think we should use a PROT_ bit for this.  It seems like
the kind of thing that could be fragile and break existing expectations.
 I don't care _that_ strongly though.