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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57103C04E69 for ; Tue, 1 Aug 2023 08:27:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232047AbjHAI1n (ORCPT ); Tue, 1 Aug 2023 04:27:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230086AbjHAI1k (ORCPT ); Tue, 1 Aug 2023 04:27:40 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EAB7F18D; Tue, 1 Aug 2023 01:27:39 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 70D67614B7; Tue, 1 Aug 2023 08:27:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18D49C433C8; Tue, 1 Aug 2023 08:27:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690878458; bh=KzvQJSYl9zliORTATgBPPvvWaET21XrF4cyjVIv9/XI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FZv0LIEbh+eOtxTtda3mi1G/HakIbe4Ec/6Cnmn9LUdCI9FrOiksmCTzlNNxzlBT4 MIXgNCSE3fyG7gBR5M5LOaV2UqtKnz2wytJDF/fHQqQV/hNxSLBaWToD6oTaw1NMRd +SIbBEMPRFEKmu2jycm5AbpsPeS4ZHVtztmmGOXbgoPPsZ80Dgj7wWuwDRLsUK0Z4l lFcVJoEbOn89u6D2oojaW5lWSBCHM+w3WZkqKSPCPB7Dl4f5cJ6OqhZ+35nM4vJ78G vP5U4ShZUHWBxh+G6+anK9+8wSAY23SydlfQLmHlgbScPb2Uawy59U4JhVgpda0KI/ 7+X51JArLXGog== Date: Tue, 1 Aug 2023 09:27:31 +0100 From: Will Deacon To: Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Baoquan He , Uladzislau Rezki , linux-fsdevel@vger.kernel.org, Jiri Olsa , Mike Galbraith , Mark Rutland , wangkefeng.wang@huawei.com, catalin.marinas@arm.com, ardb@kernel.org, David Hildenbrand , Linux regression tracking , regressions@lists.linux.dev, Matthew Wilcox , Liu Shixin , Jens Axboe , Alexander Viro , stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/kcore: reinstate bounce buffer for KCORE_TEXT regions Message-ID: <20230801082729.GA26036@willie-the-truck> References: <20230731215021.70911-1-lstoakes@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230731215021.70911-1-lstoakes@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 31, 2023 at 10:50:21PM +0100, Lorenzo Stoakes wrote: > Some architectures do not populate the entire range categorised by > KCORE_TEXT, so we must ensure that the kernel address we read from is > valid. > > Unfortunately there is no solution currently available to do so with a > purely iterator solution so reinstate the bounce buffer in this instance so > we can use copy_from_kernel_nofault() in order to avoid page faults when > regions are unmapped. > > This change partly reverts commit 2e1c0170771e ("fs/proc/kcore: avoid > bounce buffer for ktext data"), reinstating the bounce buffer, but adapts > the code to continue to use an iterator. > > Fixes: 2e1c0170771e ("fs/proc/kcore: avoid bounce buffer for ktext data") > Reported-by: Jiri Olsa > Closes: https://lore.kernel.org/all/ZHc2fm+9daF6cgCE@krava > Cc: stable@vger.kernel.org > Signed-off-by: Lorenzo Stoakes > --- > fs/proc/kcore.c | 26 +++++++++++++++++++++++++- > 1 file changed, 25 insertions(+), 1 deletion(-) Tested-by: Will Deacon I can confirm this fixes the arm64 issue reported by Mike over at [1]. Cheers, Will [1] https://lore.kernel.org/r/b39c62d29a431b023e98959578ba87e96af0e030.camel@gmx.de