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[209.132.180.67]) by mx.google.com with ESMTP id g10si1068699pgq.36.2019.06.20.18.22.37; Thu, 20 Jun 2019 18:22:52 -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=b9TAlZ5K; 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 S1726672AbfFUBU2 (ORCPT + 99 others); Thu, 20 Jun 2019 21:20:28 -0400 Received: from mail-pl1-f201.google.com ([209.85.214.201]:51453 "EHLO mail-pl1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726660AbfFUBUX (ORCPT ); Thu, 20 Jun 2019 21:20:23 -0400 Received: by mail-pl1-f201.google.com with SMTP id d2so2651756pla.18 for ; Thu, 20 Jun 2019 18:20:23 -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=ad/yNjk/bvrZoco4Mw8YoxzrZODyqSCNyrUtVdvZI0s=; b=b9TAlZ5KNSkYjsrvs/PzLlMDftAEdoVj8mEsBEzleqTi807SU2DjvF7a8CmhiMbuxb Hzn6NmDTyehRi4XpCLIg5IgZdnBCugdvbJRkEvBW6m/v9TfQlimXc8K7QlV9RPWQRBPT f4Ow8iVgacQqNXu0wQ8l7Do9OM6r9JSh1nQhJUQ3jHXWewrXQMQLMtMJjSrDMiEn5ekc a9MHX4SMQ/Opp1EiBA117qOw/ds+Xy9wXhODb0amjF3lM2AQlR4odDrH9d2dUW2FZGj0 QwDvuDjnhYK5u/K0KLCvqWRKIKOFif4rqul98NbkhtZ9j4dkupr+HqgzrEz0ZKv83ZAB IHVg== 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=ad/yNjk/bvrZoco4Mw8YoxzrZODyqSCNyrUtVdvZI0s=; b=XRdxMSiHBp1wAtc3geygDYbe04kPDJuL8Pgz0gNGNF+M6qbrVJ03NBd+zNZ7aM3oNw /rOSbZ9WP2zGnC0V9T0Eoboy/2LMmArvNKni5qXD9tscZLrfE8oKoYXFflutOTTOiLAH 8To8J50aNluKZ2U0F906ppk5WXzeYhFBQJurdBqSVtCXsl2nMnb4hzGy4zzYCNx4tbtt wW9h+j9YHF9O6/T9/41AoH+GNz4xRFq/Et3W2pwlMArGPKLhOZKy8KZLq+yQsygkHMl1 3s3TYXTKkRqH76DdpcLwmh9X/vrGP74Bf1i/lqNg6OMlqBWRuofF0iw2fQVag0uAyPen 639w== X-Gm-Message-State: APjAAAV7XmA8qmPUcBLko+2+p/SwI0mF0df1Sub/3JcX6n2/3a1rlkDe pRJkaxCpBZs/Ty7IOjDkVHWYRe2yBT1Zv9+H9lNvPA== X-Received: by 2002:a63:360d:: with SMTP id d13mr15523401pga.80.1561080022714; Thu, 20 Jun 2019 18:20:22 -0700 (PDT) Date: Thu, 20 Jun 2019 18:19:25 -0700 In-Reply-To: <20190621011941.186255-1-matthewgarrett@google.com> Message-Id: <20190621011941.186255-15-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190621011941.186255-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog Subject: [PATCH V33 14/30] x86/msr: Restrict MSR access when the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , Matthew Garrett , David Howells , 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 ++++++++ include/linux/security.h | 1 + security/lockdown/lockdown.c | 1 + 3 files changed, 10 insertions(+) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 4588414e2561..72f0ed5a93c3 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -84,6 +85,9 @@ static ssize_t msr_write(struct file *file, const char __user *buf, int err = 0; ssize_t bytes = 0; + if (security_is_locked_down(LOCKDOWN_MSR)) + return -EPERM; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -135,6 +139,10 @@ static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg) err = -EFAULT; break; } + if (security_is_locked_down(LOCKDOWN_MSR)) { + err = -EPERM; + break; + } err = wrmsr_safe_regs_on_cpu(cpu, regs); if (err) break; diff --git a/include/linux/security.h b/include/linux/security.h index 59f0ac7adfa6..81c0968e485f 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -88,6 +88,7 @@ enum lockdown_reason { LOCKDOWN_HIBERNATION, LOCKDOWN_PCI_ACCESS, LOCKDOWN_IOPORT, + LOCKDOWN_MSR, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 6e426887bb23..a01301972290 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -24,6 +24,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_HIBERNATION] = "hibernation", [LOCKDOWN_PCI_ACCESS] = "direct PCI access", [LOCKDOWN_IOPORT] = "raw io port access", + [LOCKDOWN_MSR] = "raw MSR access", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", }; -- 2.22.0.410.gd8fdbe21b5-goog