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[209.132.180.67]) by mx.google.com with ESMTP id x13si2190751pga.2.2019.04.03.17.34.30; Wed, 03 Apr 2019 17:34:44 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b="g1Y/PUQz"; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727042AbfDDAdb (ORCPT + 99 others); Wed, 3 Apr 2019 20:33:31 -0400 Received: from mail-pf1-f202.google.com ([209.85.210.202]:34610 "EHLO mail-pf1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726920AbfDDAd0 (ORCPT ); Wed, 3 Apr 2019 20:33:26 -0400 Received: by mail-pf1-f202.google.com with SMTP id j1so541154pff.1 for ; Wed, 03 Apr 2019 17:33:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=XYPTV88x6bsM2+0bDxThxX+PqaKMYNT/2nzbQ6HoL14=; b=g1Y/PUQzlr8w4VbBSoNg3vi8qaTpIpeLwblcFxEbA8qgL2rreczYP6Bcjr7XsnesyH JqyppDVnmHCPzfeUQZjpdFAH3WIzAnSKJUHQCaN2Vphxplco+8Zi9eUJxtm7PO+crggJ g4Z6IBr5ZZV+k2CogsXEWfCz6cHrWFVfx6dbJRpB4n0S6gihi2EaMdTKcxudSZhrSb1j MFW/0KS184jEDPQeKjVqRFI8ypNBAEmtUINRkS1b8X8lQu9V9onqA0UBC7sijlTciyrz Jr0PefO1jwwaoQTJIFrBlWNJ0AwlLY6GVcM6v4bXpCtj/ALGGohGwP4YOH1manzxcME0 qurA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=XYPTV88x6bsM2+0bDxThxX+PqaKMYNT/2nzbQ6HoL14=; b=BIafiIfG6zNYbn+N6gttDsrTKaUN0M3MxvVRVIeG6GSp8uxcgrMnLXYNDa99zE9WFN I1akH1NivXAnQ+zlSaKlxzvVS6ZGs/jmVZUpq3Eo49XDy65SlUWlMcBpEKRjzKyuk4SR bukOCmX9/dP6Hggym9NkwxOEMwe5MDc405NeFBFrXZYkAW2SU32nceRL+c0NebNk8Cgv nFYE+1EIAeyxqzUUuMfgSNEWRV4EZVxRj7KK6BGd+HBnpNfotU/2WU2LYLZcKMdIRVpH Fgqd1JVFMOlRlprkOwKQ2FVJS8may/q1g73LbSWsb2q38apzmw390Rf2Z29zzJqBwgrX AZdQ== X-Gm-Message-State: APjAAAXGjAoMRhV8f/vao0ZTehSkvvtgjtbGMuHOHeMtBI12KsfjvkPB /1alh7VcIUYDNVpUIfjxYbdJN5V48Yg9VZA8wexlXw== X-Received: by 2002:a62:e103:: with SMTP id q3mr83578pfh.1.1554338005084; Wed, 03 Apr 2019 17:33:25 -0700 (PDT) Date: Wed, 3 Apr 2019 17:32:34 -0700 In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> Message-Id: <20190404003249.14356-13-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190404003249.14356-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.21.0.392.gf8f6787159e-goog Subject: [PATCH V32 12/27] x86/msr: Restrict MSR access when the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Matthew Garrett , Matthew Garrett , Kees Cook , Thomas Gleixner , x86@kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Matthew Garrett Writing to MSRs should not be allowed if the kernel is locked down, since it could lead to execution of arbitrary code in kernel mode. Based on a patch by Kees Cook. Signed-off-by: Matthew Garrett Signed-off-by: David Howells Acked-by: Kees Cook Reviewed-by: Thomas Gleixner cc: x86@kernel.org --- arch/x86/kernel/msr.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 4588414e2561..731be1be52b6 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -84,6 +84,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (kernel_is_locked_down("Direct MSR access", LOCKDOWN_INTEGRITY)) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -135,6 +138,11 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EFAULT; break; } + if (kernel_is_locked_down("Direct MSR access", + LOCKDOWN_INTEGRITY)) { + err = -EPERM; + break; + } err = wrmsr_safe_regs_on_cpu(cpu, regs); if (err) break; -- 2.21.0.392.gf8f6787159e-goog