linux-kernel - Re: [RFC PATCH] x86/split_lock: Disable SLD if an unaware (out-of-tree) module enables VMX

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Message-ID: <20200408091214.GK20730@hirez.programming.kicks-ass.net>
Date:   Wed, 8 Apr 2020 11:12:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        linux-kernel@...r.kernel.org,
        "Kenneth R. Crudup" <kenny@...ix.com>,
        Jessica Yu <jeyu@...nel.org>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Xiaoyao Li <xiaoyao.li@...el.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Tony Luck <tony.luck@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        David Laight <David.Laight@...lab.com>,
        Doug Covelli <dcovelli@...are.com>
Subject: Re: [RFC PATCH] x86/split_lock: Disable SLD if an unaware
 (out-of-tree) module enables VMX

On Mon, Apr 06, 2020 at 10:10:58AM -0700, Christoph Hellwig wrote:
> On Mon, Apr 06, 2020 at 06:01:57PM +0200, Peter Zijlstra wrote:
> > Please feel free to use my pgprot_nx() and apply liberally on any
> > exported function.
> > 
> > But crucially, I don't think any of the still exported functions allows
> > getting memory in the text range, and if you want to run code outside of
> > the text range, things become _much_ harder. That said, modules
> > shouldn't be able to create executable code, full-stop (IMO).
> 
> This is what i've got for now:
> 
> http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/sanitize-vmalloc-api

Should we not also apply pgprot_nx() to __vmalloc(), that's also
EXPORT_SYMBOL().