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[209.132.180.67]) by mx.google.com with ESMTP id u30si15759405pfl.23.2019.04.03.17.36.36; Wed, 03 Apr 2019 17:36:52 -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=gglAL7lO; 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 S1726706AbfDDAdL (ORCPT + 99 others); Wed, 3 Apr 2019 20:33:11 -0400 Received: from mail-yb1-f201.google.com ([209.85.219.201]:35281 "EHLO mail-yb1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726624AbfDDAdF (ORCPT ); Wed, 3 Apr 2019 20:33:05 -0400 Received: by mail-yb1-f201.google.com with SMTP id k188so623034yba.2 for ; Wed, 03 Apr 2019 17:33:05 -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=LW7lq5jkExR1NuLSqDh6tdSVxounhx+I412qfIcDAFY=; b=gglAL7lOpCcj1Ipwnf90XUlgfXW0ddR995sFM/Mbq8P4ybdttBrpulbT63vc3U1+cP fskFmnda51fUJ0YCe6QcmmT0WwjpV6q230lV7luyLlnRRnzyev3WMyuvcm0pg4adVpUt arxvoqA9Pm39cp4hJpJkoS9XbToScJS7Fb5BEqYAblrK7kwV7D9oESDo4aJoQo6csbwZ LiPYagdCwqBoxe4hJOj1Fhf0yLyUhNsrqEsJ0IfFA9QxShzKd14vEpUEAwdtyF6MCn5x BGcvPfksazSZyXnXhg5tz5OFxe0t7MPPsA2moHkrvDM/cF7RYv7umKsZFKjdN7U/ZGGi C9Rw== 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=LW7lq5jkExR1NuLSqDh6tdSVxounhx+I412qfIcDAFY=; b=D8blhXDHJa6guvaX4+xc70WLCzB1fpvmcO/cEauH2nBLtU8u13VUGVNFX+ija+dJ2H akc4Zmd9tl92Xe1xyAipB2Mg/OW66j9ByOE0/pwb08Ik0SmWXDndTN24A0qe3dppYfEe 0ufBMzU6+eoJOpXuYOdZc9qCWU8ZeDQkiU4dfN++35W30XgB+EWLg/69UTSFmHIQgfYf QVUNq4z579LW2qya9bqPLr2uWuy7igFSEMXczDfsarHEUcppGCHM+UvOquB4xojyw4/O uEkPZScmH3SQm2MytBWqHKBAmDKPItwDRlUkbl0tyDXB7yPSpiOjPaUILOtD3GGvGzdV zRDQ== X-Gm-Message-State: APjAAAXa3HMlKk3OUvn98zvEhHggnro7u3BuAcesJwg+n2Q62e+86vcS II9DxfLvoCSxbv7WlrrF8foBn8DEoYXZcKEU8Nzdlg== X-Received: by 2002:a25:9086:: with SMTP id t6mr543895ybl.77.1554337984697; Wed, 03 Apr 2019 17:33:04 -0700 (PDT) Date: Wed, 3 Apr 2019 17:32:26 -0700 In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> Message-Id: <20190404003249.14356-5-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 04/27] 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, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Matthew Garrett , Matthew Garrett , Dave Young , kexec@lists.infradead.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 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 cc: kexec@lists.infradead.org --- kernel/kexec.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/kexec.c b/kernel/kexec.c index 68559808fdfa..57047acc9a36 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -207,6 +207,14 @@ 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 + */ + if (kernel_is_locked_down("kexec of unsigned images", + LOCKDOWN_INTEGRITY)) + return -EPERM; + /* * Verify we have a legal set of flags * This leaves us room for future extensions. -- 2.21.0.392.gf8f6787159e-goog