From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2748CC4321E for ; Fri, 7 Sep 2018 21:14:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D911120844 for ; Fri, 7 Sep 2018 21:14:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D911120844 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728368AbeIHB5K (ORCPT ); Fri, 7 Sep 2018 21:57:10 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:42088 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727638AbeIHB5J (ORCPT ); Fri, 7 Sep 2018 21:57:09 -0400 Received: from localhost (ip-213-127-74-90.ip.prioritytelecom.net [213.127.74.90]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id DA256FD4; Fri, 7 Sep 2018 21:14:22 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jason Gunthorpe , Leon Romanovsky , Kees Cook Subject: [PATCH 4.18 045/145] overflow.h: Add arithmetic shift helper Date: Fri, 7 Sep 2018 23:08:31 +0200 Message-Id: <20180907210908.213674540@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180907210903.617721278@linuxfoundation.org> References: <20180907210903.617721278@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 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 4.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jason Gunthorpe commit 0c66847793d1982d1083dc6f7adad60fa265ce9c upstream. Add shift_overflow() helper to assist driver authors in ensuring that shift operations don't cause overflows or other odd conditions. Signed-off-by: Jason Gunthorpe Signed-off-by: Leon Romanovsky [kees: tweaked comments and commit log, dropped unneeded assignment] Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- include/linux/overflow.h | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) --- a/include/linux/overflow.h +++ b/include/linux/overflow.h @@ -202,6 +202,37 @@ #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */ +/** check_shl_overflow() - Calculate a left-shifted value and check overflow + * + * @a: Value to be shifted + * @s: How many bits left to shift + * @d: Pointer to where to store the result + * + * Computes *@d = (@a << @s) + * + * Returns true if '*d' cannot hold the result or when 'a << s' doesn't + * make sense. Example conditions: + * - 'a << s' causes bits to be lost when stored in *d. + * - 's' is garbage (e.g. negative) or so large that the result of + * 'a << s' is guaranteed to be 0. + * - 'a' is negative. + * - 'a << s' sets the sign bit, if any, in '*d'. + * + * '*d' will hold the results of the attempted shift, but is not + * considered "safe for use" if false is returned. + */ +#define check_shl_overflow(a, s, d) ({ \ + typeof(a) _a = a; \ + typeof(s) _s = s; \ + typeof(d) _d = d; \ + u64 _a_full = _a; \ + unsigned int _to_shift = \ + _s >= 0 && _s < 8 * sizeof(*d) ? _s : 0; \ + *_d = (_a_full << _to_shift); \ + (_to_shift != _s || *_d < 0 || _a < 0 || \ + (*_d >> _to_shift) != _a); \ +}) + /** * array_size() - Calculate size of 2-dimensional array. *