From patchwork Tue Jan 29 00:34:22 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Edgecombe, Rick P" X-Patchwork-Id: 10785157 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 C0EF21874 for ; Tue, 29 Jan 2019 00:39:55 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B10D92B4C4 for ; Tue, 29 Jan 2019 00:39:55 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A50202B4D3; Tue, 29 Jan 2019 00:39:55 +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=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable 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 5E0D22B4EA for ; Tue, 29 Jan 2019 00:39:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727698AbfA2AjX (ORCPT ); Mon, 28 Jan 2019 19:39:23 -0500 Received: from mga06.intel.com ([134.134.136.31]:5088 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727672AbfA2AjX (ORCPT ); Mon, 28 Jan 2019 19:39:23 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Jan 2019 16:39:12 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,535,1539673200"; d="scan'208";a="133921945" Received: from rpedgeco-desk5.jf.intel.com ([10.54.75.79]) by orsmga001.jf.intel.com with ESMTP; 28 Jan 2019 16:39:12 -0800 From: Rick Edgecombe To: Andy Lutomirski , Ingo Molnar Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com, Thomas Gleixner , Borislav Petkov , Nadav Amit , Dave Hansen , Peter Zijlstra , linux_dti@icloud.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, akpm@linux-foundation.org, kernel-hardening@lists.openwall.com, linux-mm@kvack.org, will.deacon@arm.com, ard.biesheuvel@linaro.org, kristen@linux.intel.com, deneen.t.dock@intel.com, Nadav Amit , Masami Hiramatsu , Rick Edgecombe Subject: [PATCH v2 20/20] x86/alternative: comment about module removal races Date: Mon, 28 Jan 2019 16:34:22 -0800 Message-Id: <20190129003422.9328-21-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190129003422.9328-1-rick.p.edgecombe@intel.com> References: <20190129003422.9328-1-rick.p.edgecombe@intel.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Nadav Amit Add a comment to clarify that users of text_poke() must ensure that no races with module removal take place. Cc: Masami Hiramatsu Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe --- arch/x86/kernel/alternative.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 81876e3ef3fd..cc3b6222857a 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -807,6 +807,11 @@ static void *__text_poke(void *addr, const void *opcode, size_t len) * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. + * + * Note that the caller must ensure that if the modified code is part of a + * module, the module would not be removed during poking. This can be achieved + * by registering a module notifier, and ordering module removal and patching + * trough a mutex. */ void *text_poke(void *addr, const void *opcode, size_t len) {