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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id D1197D3B7E2 for ; Tue, 9 Dec 2025 01:30:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type: Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-ID:Date :Subject:CC:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=EaN56bNHDdaDU4xaAsWBhkgyh1tI7ov9fWzaVcBUtA8=; b=TB6ZHbp4wZ8PYqAQuIowDMuAsK ylBt+s9SBkNypfhyUKzVw01EZ31+34pMh8Pi+ZsxjBUYKDjf5zeL1pYleTLZeYGkvqiGbI5/a/oQx 9xUL+wjep7MHDrQ05qGxkJ6a4yVmdV7tP39tUZckPu/IFQnHSsEk3gmUPU96BXX5hTZbnYqj0VJos MgapgO0tSPg9v1bZu70oqEpqdDgZjuFC+gWGMVSaHwR+1fIN5e1Qm1bH3No40eMXMABYHGKvSjnr4 pQ01s6pVj41Y4Jr5bjw6rAcYhD5z0XS3ozgQyR9fBbg8HX+gTlw5siuHzr+HteA5RKHgoIeskNliR i29/JwHQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vSmYp-0000000DhlM-2c2R; Tue, 09 Dec 2025 01:30:39 +0000 Received: from canpmsgout01.his.huawei.com ([113.46.200.216]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vSmYn-0000000Dhkt-0PNU for linux-arm-kernel@lists.infradead.org; Tue, 09 Dec 2025 01:30:39 +0000 dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=EaN56bNHDdaDU4xaAsWBhkgyh1tI7ov9fWzaVcBUtA8=; b=S0Onu6kYl9D8cUbpZTYsCtWPafYB7opD91x91GJEgAsQozI1jQu1RjI3r+YUxODEgOrBO16G4 4rudE/tl/ISBlGPl73FxPE7obeVr4McmRTQApR9kNXgBFAfoNDCG51gTbJjvPO6iIYhfcJjKNJ/ i74oJ0pNGViS2Nr3mDxm6bI= Received: from mail.maildlp.com (unknown [172.19.163.252]) by canpmsgout01.his.huawei.com (SkyGuard) with ESMTPS id 4dQLpK2wChz1T4GD; Tue, 9 Dec 2025 09:28:25 +0800 (CST) Received: from kwepemj100009.china.huawei.com (unknown [7.202.194.3]) by mail.maildlp.com (Postfix) with ESMTPS id D0A49180BD8; Tue, 9 Dec 2025 09:30:25 +0800 (CST) Received: from DESKTOP-A37P9LK.china.huawei.com (10.67.109.17) by kwepemj100009.china.huawei.com (7.202.194.3) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 9 Dec 2025 09:30:24 +0800 From: Xie Yuanbin To: CC: , , , , , , , , , , , , , , , , Subject: Re: [Bug report] hash_name() may cross page boundary and trigger sleep in RCU context Date: Tue, 9 Dec 2025 09:30:21 +0800 Message-ID: <20251209013021.2537-1-xieyuanbin1@huawei.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.67.109.17] X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To kwepemj100009.china.huawei.com (7.202.194.3) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251208_173037_643347_A6F6A800 X-CRM114-Status: GOOD ( 14.53 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 8 Dec 2025 15:43:56 +0000, Russell King wrote: > On Mon, Dec 08, 2025 at 09:18:42PM +0800, Xie Yuanbin wrote: >> I had indeed been lacking in consideration regarding do_alignment() >> before, so thank you for reply. But, may I ask that, is there a scenario >> where user-mode access to kernel addresses causes an alignment fault >> (do_alignment())? > > If you mean, won't permission errors be detected first, then no. > Alignment is one of the first things that is checked if alignment > faults are enabled. > > So yes, if userspace attempts an unaigned load of a kernel address, > and the CPU does not support / have enabled unaigned load support, > then we will get a data abort with the FSR indicating an alignment > fault. So do_alignment() wil be entered. > > Whether branch predictor handling needs to happen in this path is > a separate question, but as it's highly likely we'll take an > exception anyway and userspace is doing Bad Stuff, I feel it's > better to be over-cautious. Thanks for your reply. I know it now, and thank you.