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=unavailable 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 44819C33CAF for ; Thu, 16 Jan 2020 17:50:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1EB7B246D9 for ; Thu, 16 Jan 2020 17:50:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579197027; bh=NH7YmaENed7733PiOVCPiTH7DV/SfeLsD2y7DmbM7Ug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rz6E+J1z3O+/2I54NFOxaZlc1TTUoUgMFTXUdBcl/6JC+tKHaxVVSh+Qp18bTTtZN zDJUvWYVXBN1pQDl9P7bAvT4CqK1Zm93MrZfrNmVWVGklTqHvctJ/5U9KP4JHr+VkU YZqSug5SXvJS1gzKglYi7OyEBzdb+DLwRcuMX8Zs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394323AbgAPRuV (ORCPT ); Thu, 16 Jan 2020 12:50:21 -0500 Received: from mail.kernel.org ([198.145.29.99]:38164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2406531AbgAPRpw (ORCPT ); Thu, 16 Jan 2020 12:45:52 -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 B3717246A7; Thu, 16 Jan 2020 17:45:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579196751; bh=NH7YmaENed7733PiOVCPiTH7DV/SfeLsD2y7DmbM7Ug=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Bc35I8PM30FnKztSBDxfYPmzHG5MG1SLjU9D5o3ir8lzPupNzP2vV6NVoTUAcbcso M7fWiFSFDbKSCfYZIPX6HkQD9/515vBEcjEzJkJr6Qd1ynrpWz9fp/G1xuDR3rsq6r rd0wSA2ufUvxiQDi3nKlIS0BobL33Z8mckyTCBAE= 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 4.4 128/174] Partially revert "kfifo: fix kfifo_alloc() and kfifo_init()" Date: Thu, 16 Jan 2020 12:42:05 -0500 Message-Id: <20200116174251.24326-128-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200116174251.24326-1-sashal@kernel.org> References: <20200116174251.24326-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 90ba1eb1df06..a94227c55551 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