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[209.132.180.67]) by mx.google.com with ESMTP id y9si14474484pgg.15.2019.04.03.17.36.02; Wed, 03 Apr 2019 17:36:17 -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=HrnnfxtE; 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 S1727006AbfDDAda (ORCPT + 99 others); Wed, 3 Apr 2019 20:33:30 -0400 Received: from mail-vk1-f202.google.com ([209.85.221.202]:46943 "EHLO mail-vk1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726966AbfDDAd2 (ORCPT ); Wed, 3 Apr 2019 20:33:28 -0400 Received: by mail-vk1-f202.google.com with SMTP id v82so435158vkd.13 for ; Wed, 03 Apr 2019 17:33:28 -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=aQw0KGeWmvPzPQJC9aCiMXHo5RCdIiAFpbvhdBtqfOA=; b=HrnnfxtEOmZgJzYuk+1NGAEVH3FcUFjd6/CBWrK13gcpvb388nqYaCopTOLyHeiL1d BKx8619edH1V2dmHSMJXG+k3mIUlblQzV2u/zO0e4fFTXaPhYH3qkk2oBZtOPkDf/pMH c54kprWqcu9bnxwX2huhYfWI0NK19dx+cOTVdTShh6O9RpDn5d1CRWLTj74UYSVkLfjk m9UNjHC3gaOX9OtPbO5zNNbbdyPtrCAFi3EKo2W41SCPOU88rp2S8NL6uCUmQdKvJubH 3qMyUCCEogMiavG6CtQUFSXB3/s/iNE8LHMbqsYvZCIifSgPCsE7EMCoYzlvMPlip49W ZGow== 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=aQw0KGeWmvPzPQJC9aCiMXHo5RCdIiAFpbvhdBtqfOA=; b=PkMuZl5gMk3ScBORff2GjRQ5OfG6n432Yc3r8hwWwbtwPVxdnXH1ufWByZE7Rn36cq f6Qh3IUz2U7SgIJaCaGXnZIQwfu1a3snOp13yyLT1tRqgNOzpXyHzEcuFI9MPA+peGGl MK4kZYkzyEHjxBUpazhyh8rOZtuy2pr65GtowDQ5JgJx7HWET50rObOtfO/avTdg7ab/ VrwGSNf17N8zVTZKO0bM2bWCGRWYdLO7ZkAsHX89vFB59R07x7EOfQeXM0Qgd0rmetTy 1T0z/OPcRL0JGiSDIZXOsd/twHKHFkC6JAMgWJbEtRteaE5tLQe3ULLAk9wqkjsYXLYR DhPg== X-Gm-Message-State: APjAAAXYtsKQHpousQFIiaqvh4I0RHNYhjSxmD6mDfO9dVDYph9KTbzS i6y15NuHfV9brvd0SVd+UA62vRoFLh1PyGmKbXY7pw== X-Received: by 2002:a1f:9010:: with SMTP id s16mr372950vkd.12.1554338007705; Wed, 03 Apr 2019 17:33:27 -0700 (PDT) Date: Wed, 3 Apr 2019 17:32:35 -0700 In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> Message-Id: <20190404003249.14356-14-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 13/27] ACPI: Limit access to custom_method 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 , linux-acpi@vger.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 custom_method effectively allows arbitrary access to system memory, making it possible for an attacker to circumvent restrictions on module loading. Disable it if the kernel is locked down. Signed-off-by: Matthew Garrett Signed-off-by: David Howells cc: linux-acpi@vger.kernel.org --- drivers/acpi/custom_method.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index 4451877f83b6..37de3cd84493 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -29,6 +29,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, struct acpi_table_header table; acpi_status status; + if (kernel_is_locked_down("ACPI custom methods", LOCKDOWN_INTEGRITY)) + return -EPERM; + if (!(*ppos)) { /* parse the table header to get the table length */ if (count <= sizeof(struct acpi_table_header)) -- 2.21.0.392.gf8f6787159e-goog