From patchwork Thu Jul 18 19:43:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11049463 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2D31A746 for ; Thu, 18 Jul 2019 19:44:38 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1AE9C2883B for ; Thu, 18 Jul 2019 19:44:38 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0DCAA2889C; Thu, 18 Jul 2019 19:44:38 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A22EB2883B for ; Thu, 18 Jul 2019 19:44:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391558AbfGRTof (ORCPT ); Thu, 18 Jul 2019 15:44:35 -0400 Received: from mail-pg1-f201.google.com ([209.85.215.201]:55043 "EHLO mail-pg1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391549AbfGRTof (ORCPT ); Thu, 18 Jul 2019 15:44:35 -0400 Received: by mail-pg1-f201.google.com with SMTP id m17so8313506pgh.21 for ; Thu, 18 Jul 2019 12:44:34 -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=eu667FWqsyv1eiS+2MgLd1pI1Yi90NnjxQ1QKJHeSZs=; b=ohrtYog4gGPeInnSgPNEoQxrDXPaBrUloNn0kHObJFwMww/WL/1QitIjfRTdQ7Io3l 3SFmno+zU0LHqnjj1iwf/EcXC0mkATM1jwJSktN3EWogC7qhjF9T+4Vc2XXS/dPtmlKX mz5jQECVWQ2KxykCHqcx7Q4Oj8ogBpTDoACnxdCUgqa3Ot4HPl0AkiJXF4fk6mY7//oL 7PbCHo+Yh6dVRTJvVO6GMzSfDJ2XD8gX5qc9TCAmUHKXJA2d2DOUhz+oq/Fg4W64rGof PvjyvsAmKWx9isgpl4njBFhx7acc40bmEcgvG4s2a7Usp9NXUY50lVDgZ8lf+u3ipVh8 +y9A== 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=eu667FWqsyv1eiS+2MgLd1pI1Yi90NnjxQ1QKJHeSZs=; b=jHJRd685cRnDtlvULhw9ysuR5a15Omo4JOZ6K/BniC0E0un3ToCOHwRzG/3tiJ8DjQ jrFR4/g3sT+Oh0jxih8yHLTGQmNTCNTtz5t0bt5TKIZa25uvIGnDoM5VYxAXpvMH3TUn KwvwNQZwVdwD4v3n82czznBH3f4HHQJQnPZqtRPMlwAcHfb7qMVnr8Ua0+7zCrtF5ZSD 5MnOHSQQ1fN3HvrxoPmwe+JUr7K6VqSiZuhA9G4Y5A3fYnyMblsWhmRIha/9a417sjKp Hpuqaq/tLKQJh6WFR2CwMDzqbltz4/ajzeJhw53uC2p6j+oGbmju1GvKlMo9nRDTg1M+ 2lYA== X-Gm-Message-State: APjAAAWOzV9Nv/vWcYmFKBl3QfyDbaeDOFEgfMlrHpO0viqmqXXF+q6H z8yT4TiVdNesseHDKs5VoV0Je1IDbg4rpItR3f09Xg== X-Google-Smtp-Source: APXvYqz2hh3xf3NNVSMQwnKxLqxoPr5fEA/x4WWO1oTU5T/O29MD4PGWgIppNaZkbdLHJf6ADY0SDRBtGzSuhQYGFEqqag== X-Received: by 2002:a65:500d:: with SMTP id f13mr48703316pgo.151.1563479074121; Thu, 18 Jul 2019 12:44:34 -0700 (PDT) Date: Thu, 18 Jul 2019 12:43:52 -0700 In-Reply-To: <20190718194415.108476-1-matthewgarrett@google.com> Message-Id: <20190718194415.108476-7-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190718194415.108476-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.510.g264f2c817a-goog Subject: [PATCH V36 06/29] kexec_load: Disable at runtime if the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Matthew Garrett , David Howells , Matthew Garrett , Dave Young , Kees Cook , kexec@lists.infradead.org Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Matthew Garrett The kexec_load() syscall permits the loading and execution of arbitrary code in ring 0, which is something that lock-down is meant to prevent. It makes sense to disable kexec_load() in this situation. This does not affect kexec_file_load() syscall which can check for a signature on the image to be booted. Signed-off-by: David Howells Signed-off-by: Matthew Garrett Acked-by: Dave Young Reviewed-by: Kees Cook cc: kexec@lists.infradead.org --- include/linux/security.h | 1 + kernel/kexec.c | 8 ++++++++ security/lockdown/lockdown.c | 1 + 3 files changed, 10 insertions(+) diff --git a/include/linux/security.h b/include/linux/security.h index 9458152601b5..69c5de539e9a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -105,6 +105,7 @@ enum lockdown_reason { LOCKDOWN_NONE, LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_DEV_MEM, + LOCKDOWN_KEXEC, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/kernel/kexec.c b/kernel/kexec.c index 1b018f1a6e0d..bc933c0db9bf 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -205,6 +205,14 @@ static inline int kexec_load_check(unsigned long nr_segments, if (result < 0) return result; + /* + * kexec can be used to circumvent module loading restrictions, so + * prevent loading in that case + */ + result = security_locked_down(LOCKDOWN_KEXEC); + if (result) + return result; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index d2ef29d9f0b2..6f302c156bc8 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", + [LOCKDOWN_KEXEC] = "kexec of unsigned images", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };