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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6281FC2BB55 for ; Wed, 15 Apr 2020 10:08:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4375220768 for ; Wed, 15 Apr 2020 10:08:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2896200AbgDOKIs (ORCPT ); Wed, 15 Apr 2020 06:08:48 -0400 Received: from foss.arm.com ([217.140.110.172]:41338 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2896152AbgDOKIp (ORCPT ); Wed, 15 Apr 2020 06:08:45 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 748491063; Wed, 15 Apr 2020 03:08:44 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9E1BF3F68F; Wed, 15 Apr 2020 03:08:43 -0700 (PDT) Date: Wed, 15 Apr 2020 11:08:37 +0100 From: Catalin Marinas To: Will Deacon Cc: Vincenzo Frascino , Mark Rutland , linux-arm-kernel@lists.infradead.org, stable@vger.kernel.org Subject: Re: [PATCH 1/5] arm64: vdso: don't free unallocated pages Message-ID: <20200415100836.GB6526@gaia> References: <20200414104252.16061-1-mark.rutland@arm.com> <20200414104252.16061-2-mark.rutland@arm.com> <20200414132751.GF2486@C02TD0UTHF1T.local> <8681c958-0fd9-130e-f7bb-99bfd3a027cb@arm.com> <20200414151033.GA30288@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200414151033.GA30288@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, Apr 14, 2020 at 04:10:35PM +0100, Will Deacon wrote: > On Tue, Apr 14, 2020 at 03:53:45PM +0100, Vincenzo Frascino wrote: > > On 4/14/20 2:27 PM, Mark Rutland wrote: > > > On Tue, Apr 14, 2020 at 01:50:38PM +0100, Vincenzo Frascino wrote: > > >> On 4/14/20 11:42 AM, Mark Rutland wrote: > > >>> The aarch32_vdso_pages[] array never has entries allocated in the C_VVAR > > >>> or C_VDSO slots, and as the array is zero initialized these contain > > >>> NULL. > > >>> > > >>> However in __aarch32_alloc_vdso_pages() when > > >>> aarch32_alloc_kuser_vdso_page() fails we attempt to free the page whose > > >>> struct page is at NULL, which is obviously nonsensical. > > >> > > >> Could you please explain why do you think that free(NULL) is "nonsensical"? > > > > > > Regardless of the below, can you please explain why it is sensical? I'm > > > struggling to follow your argument here. > > > > free(NULL) is a no-operation ("no action occurs") according to the C standard > > (ISO-IEC 9899 paragraph 7.20.3.2). Hence this should not cause any bug if the > > allocator is correctly implemented. From what I can see the implementation of > > the page allocator honors this assumption. > > > > Since you say it is a bug (providing evidence), we might have to investigate > > because probably there is an issue somewhere else. > > Not sure why you feel the need to throw the C standard around -- the patch > from Mark looks obviously like the right thing to do to me, so: > > Acked-by: Will Deacon > > Catalin -- please take this one as a fix so that I can queue the rest of > the patches for 5.8 once it's hit mainline. I queued this patch for -rc2. Thanks. -- Catalin 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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 2C84BC2BA19 for ; Wed, 15 Apr 2020 10:08:49 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EBEA820768 for ; Wed, 15 Apr 2020 10:08:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="le9DImFg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EBEA820768 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=YxV14g3c+fQUn5BwMldnZqjKaerTPifCbIAFTyJXI+w=; b=le9DImFgm3kdrX OkN7Tumqfa9+lIoB+powWBPYiy7YMD89w2LnMXzVtHwunBq95rirYN5i5OKBjLQwoUTEIFYyRvuh6 Z7T5hjuCl/ad+MBFTlw32PaAaJDUWbfKjDmvclcF6uhrfsDFKcqbFAtPCQmEGVRqpKA5eLGZAioe2 4QOuOfBSfxe7jiz26egs5hpC0Sq8lN+VMeRqz/sZEA0rOa+j9Nrg8VQ/nVacx6JAlhFH3gVeC+gtl ScrE1PjzeuXdUvyZOGP8OkTPGHRy6YFhlneMIkO8fFyrNOftgU4Zww9AcDEbO1pJLe7jmpzrcqjwC 2N8Iea7roKREztyZ+DhA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOeyO-0006Ai-HK; Wed, 15 Apr 2020 10:08:48 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jOeyL-0006AK-2P for linux-arm-kernel@lists.infradead.org; Wed, 15 Apr 2020 10:08:46 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 748491063; Wed, 15 Apr 2020 03:08:44 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9E1BF3F68F; Wed, 15 Apr 2020 03:08:43 -0700 (PDT) Date: Wed, 15 Apr 2020 11:08:37 +0100 From: Catalin Marinas To: Will Deacon Subject: Re: [PATCH 1/5] arm64: vdso: don't free unallocated pages Message-ID: <20200415100836.GB6526@gaia> References: <20200414104252.16061-1-mark.rutland@arm.com> <20200414104252.16061-2-mark.rutland@arm.com> <20200414132751.GF2486@C02TD0UTHF1T.local> <8681c958-0fd9-130e-f7bb-99bfd3a027cb@arm.com> <20200414151033.GA30288@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200414151033.GA30288@willie-the-truck> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200415_030845_152454_5102E2EE X-CRM114-Status: GOOD ( 19.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Vincenzo Frascino , stable@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Apr 14, 2020 at 04:10:35PM +0100, Will Deacon wrote: > On Tue, Apr 14, 2020 at 03:53:45PM +0100, Vincenzo Frascino wrote: > > On 4/14/20 2:27 PM, Mark Rutland wrote: > > > On Tue, Apr 14, 2020 at 01:50:38PM +0100, Vincenzo Frascino wrote: > > >> On 4/14/20 11:42 AM, Mark Rutland wrote: > > >>> The aarch32_vdso_pages[] array never has entries allocated in the C_VVAR > > >>> or C_VDSO slots, and as the array is zero initialized these contain > > >>> NULL. > > >>> > > >>> However in __aarch32_alloc_vdso_pages() when > > >>> aarch32_alloc_kuser_vdso_page() fails we attempt to free the page whose > > >>> struct page is at NULL, which is obviously nonsensical. > > >> > > >> Could you please explain why do you think that free(NULL) is "nonsensical"? > > > > > > Regardless of the below, can you please explain why it is sensical? I'm > > > struggling to follow your argument here. > > > > free(NULL) is a no-operation ("no action occurs") according to the C standard > > (ISO-IEC 9899 paragraph 7.20.3.2). Hence this should not cause any bug if the > > allocator is correctly implemented. From what I can see the implementation of > > the page allocator honors this assumption. > > > > Since you say it is a bug (providing evidence), we might have to investigate > > because probably there is an issue somewhere else. > > Not sure why you feel the need to throw the C standard around -- the patch > from Mark looks obviously like the right thing to do to me, so: > > Acked-by: Will Deacon > > Catalin -- please take this one as a fix so that I can queue the rest of > the patches for 5.8 once it's hit mainline. I queued this patch for -rc2. Thanks. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel