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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 30836C33CAF for ; Thu, 16 Jan 2020 18:44:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 010EF2073A for ; Thu, 16 Jan 2020 18:44:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579200247; bh=ENH9qJZ2wnMw/iROLzTDu5Co9VYRibguqz45d7YFmBw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=oiriaa4jwYIgISojj/8CnfIT5c4Apx/iKhozin9My8Aa8pqfsMO8DXKVq2T5gE7tl dG2eqzeTTpGbOMF8i3MDwEFQeJdufmmQnYXFDcbyVWwE7fqKV2IutHkX1yb09Z8The SL3p/+adqOAgIaR+0uL6vLNTLMzuavMe290J1vlY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388509AbgAPSoF (ORCPT ); Thu, 16 Jan 2020 13:44:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:50784 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388664AbgAPRLE (ORCPT ); Thu, 16 Jan 2020 12:11:04 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6B3B12469A; Thu, 16 Jan 2020 17:11:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579194663; bh=ENH9qJZ2wnMw/iROLzTDu5Co9VYRibguqz45d7YFmBw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WUxbT6O22URtmKqJbdn/n/rV8WwTAYrlOT9iPhrGailAS2qMdRbL4wyl1eTP6FhrK U/rOLw9cc5g6lCxtUOdF92BLd/x/yGI6AZpsnUdTHsXOKrgmN8tb+13LWXWMLhzU8r iQmn1UTPIOJtGKECArMkYof/j+m4CSN/HSic3W2c= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Linus Torvalds , laokz , Stefani Seibold , Andrew Morton , Dan Carpenter , Greg KH , Kees Cook , Will Deacon , Sasha Levin Subject: [PATCH AUTOSEL 4.19 513/671] Partially revert "kfifo: fix kfifo_alloc() and kfifo_init()" Date: Thu, 16 Jan 2020 12:02:31 -0500 Message-Id: <20200116170509.12787-250-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200116170509.12787-1-sashal@kernel.org> References: <20200116170509.12787-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 015656aa8182..6320ab91e343 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