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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 A26C8C2D0DB for ; Tue, 28 Jan 2020 14:12:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7AD882468D for ; Tue, 28 Jan 2020 14:12:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580220742; bh=8WJOEl1qWNSyxzfiwg8ltidaByHuIaW8yhNEakVLz/8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zmX5WkRXO3ueqlcVFGND9+b/g4Egb8Hwsdu/awidJgtneIo0JVHRcsKMbP5IAW4iI W9IoOQBmPT1aCffFh7S4sAzZiNduwwt+L6l7jNW+8fpfeQS4rVs7Zmgl5HN8SDrAqZ FZ7bsaUiIctlKGI3mDha3zgrgWmtxCctIjiHX1lA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726718AbgA1OMV (ORCPT ); Tue, 28 Jan 2020 09:12:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:33558 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728320AbgA1OMT (ORCPT ); Tue, 28 Jan 2020 09:12:19 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4458620678; Tue, 28 Jan 2020 14:12:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580220738; bh=8WJOEl1qWNSyxzfiwg8ltidaByHuIaW8yhNEakVLz/8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=miEoF7OaU5VsHpBb2616k+Nn8YA7i9k5Z3DB0bLddWqy/CnpPKJDF3fFFhT45j3lI QERtKACZBrjNL+k33aN1H5K/j7nbXBtFDzdkqcSLy2FBlGideDaxvt5HkusPQbxbb/ uDHIMhqIPymOeYDfgIpB2EV8hsFgAoEZs64K6b3I= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, laokz , Stefani Seibold , Andrew Morton , Dan Carpenter , Greg KH , Kees Cook , Will Deacon , Linus Torvalds , Sasha Levin Subject: [PATCH 4.4 128/183] Partially revert "kfifo: fix kfifo_alloc() and kfifo_init()" Date: Tue, 28 Jan 2020 15:05:47 +0100 Message-Id: <20200128135842.651838815@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200128135829.486060649@linuxfoundation.org> References: <20200128135829.486060649@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Linus Torvalds [ Upstream commit ab9bb6318b0967671e0c9b6537c1537d51ca4f45 ] Commit dfe2a77fd243 ("kfifo: fix kfifo_alloc() and kfifo_init()") made the kfifo code round the number of elements up. That was good for __kfifo_alloc(), but it's actually wrong for __kfifo_init(). The difference? __kfifo_alloc() will allocate the rounded-up number of elements, but __kfifo_init() uses an allocation done by the caller. We can't just say "use more elements than the caller allocated", and have to round down. The good news? All the normal cases will be using power-of-two arrays anyway, and most users of kfifo's don't use kfifo_init() at all, but one of the helper macros to declare a KFIFO that enforce the proper power-of-two behavior. But it looks like at least ibmvscsis might be affected. The bad news? Will Deacon refers to an old thread and points points out that the memory ordering in kfifo's is questionable. See https://lore.kernel.org/lkml/20181211034032.32338-1-yuleixzhang@tencent.com/ for more. Fixes: dfe2a77fd243 ("kfifo: fix kfifo_alloc() and kfifo_init()") Reported-by: laokz Cc: Stefani Seibold Cc: Andrew Morton Cc: Dan Carpenter Cc: Greg KH Cc: Kees Cook Cc: Will Deacon Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- lib/kfifo.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/lib/kfifo.c b/lib/kfifo.c index 90ba1eb1df06e..a94227c555510 100644 --- a/lib/kfifo.c +++ b/lib/kfifo.c @@ -82,7 +82,8 @@ int __kfifo_init(struct __kfifo *fifo, void *buffer, { size /= esize; - size = roundup_pow_of_two(size); + if (!is_power_of_2(size)) + size = rounddown_pow_of_two(size); fifo->in = 0; fifo->out = 0; -- 2.20.1