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[198.145.29.99]) by mx.google.com with ESMTPS id a14si5875098pgm.206.2019.06.29.16.45.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 29 Jun 2019 16:45:07 -0700 (PDT) Received-SPF: pass (google.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=L9zsQCD3; spf=pass (google.com: domain of luto@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=luto@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mail-wm1-f47.google.com (mail-wm1-f47.google.com [209.85.128.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 10A6C217F4 for ; Sat, 29 Jun 2019 23:45:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561851907; bh=NO9SldPrvEHCV9L05HomDu1WyC6FUgdLlHc97KSTRsQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=L9zsQCD3SME4yCdiZ91gR5mu3dTU7iHytvauDPWLVWJ5PVYhrkz4Xa1e7uv4wAgV3 dn6A6uxhscIfZ/fM0Q/M50uV8Zprd9O/fI/u2BZF1R7eLQPpJWxVUZ9macy7ZQ9u1d B6qcP8VfgVBU5+U66FxTgTcWis+nQEC2Uneo6t/g= Received: by mail-wm1-f47.google.com with SMTP id c6so12285048wml.0 for ; Sat, 29 Jun 2019 16:45:06 -0700 (PDT) X-Received: by 2002:a1c:9a53:: with SMTP id c80mr11059844wme.173.1561851905663; Sat, 29 Jun 2019 16:45:05 -0700 (PDT) MIME-Version: 1.0 References: <20190628194158.2431-1-yu-cheng.yu@intel.com> <20190628194158.2431-3-yu-cheng.yu@intel.com> In-Reply-To: <20190628194158.2431-3-yu-cheng.yu@intel.com> From: Andy Lutomirski Date: Sat, 29 Jun 2019 16:44:54 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC PATCH 3/3] Prevent user from writing to IBT bitmap. To: Yu-cheng Yu Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jun 28, 2019 at 12:50 PM Yu-cheng Yu wrote: > > The IBT bitmap is visiable from user-mode, but not writable. > > Signed-off-by: Yu-cheng Yu > > --- > arch/x86/mm/fault.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > index 59f4f66e4f2e..231196abb62e 100644 > --- a/arch/x86/mm/fault.c > +++ b/arch/x86/mm/fault.c > @@ -1454,6 +1454,13 @@ void do_user_addr_fault(struct pt_regs *regs, > * we can handle it.. > */ > good_area: > +#define USER_MODE_WRITE (FAULT_FLAG_WRITE | FAULT_FLAG_USER) > + if (((flags & USER_MODE_WRITE) == USER_MODE_WRITE) && > + (vma->vm_flags & VM_IBT)) { > + bad_area_access_error(regs, hw_error_code, address, vma); > + return; > + } > + Just make the VMA have VM_WRITE and VM_MAYWRITE clear. No new code like this should be required.