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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D0D3EC433E0 for ; Thu, 25 Mar 2021 22:13:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A4BAD61A28 for ; Thu, 25 Mar 2021 22:13:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230505AbhCYWMy (ORCPT ); Thu, 25 Mar 2021 18:12:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38704 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230285AbhCYWM0 (ORCPT ); Thu, 25 Mar 2021 18:12:26 -0400 Received: from mail-pg1-x52e.google.com (mail-pg1-x52e.google.com [IPv6:2607:f8b0:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D358BC06174A for ; Thu, 25 Mar 2021 15:12:25 -0700 (PDT) Received: by mail-pg1-x52e.google.com with SMTP id r17so3254896pgi.0 for ; Thu, 25 Mar 2021 15:12:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=axtens.net; s=google; h=from:to:cc:subject:in-reply-to:references:date:message-id :mime-version; bh=DYUjSc1vAjGrU7Upg//GwkOyzK5I7lVAlzXmtTspUfQ=; b=il68+HICDOpc315fwdeM5b5fe9U1OGmrgs8JA1Q4TimO7bh5f4kHrj87ZxXtRKuDVK lp+v5uD/1rHtyYh4J4hyvUcDa0a5JtY3jBtNgDZvnFz8WNrBCg+rxevJntyvuxlbO3yG LfmGszSXA9rGeLIiuuQTOjGLoQ1VPel2tP9d8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=DYUjSc1vAjGrU7Upg//GwkOyzK5I7lVAlzXmtTspUfQ=; b=avpZXpK9vtn2iDAzX3CfFjRiBF1b5ZcC8+ehl+0+y57wHkQU9TJJ3hC29us4zItVbu Wwjsf8sYELQlcCRxtlBjm9XZxf1vgf/7oqBdDkWTXCqmC7xy2CWIR8I6FpE8JB28Fq2W r4pcqPCW5c6YNCChi9tUJvpa9F6nb6czU/T4iec/Dxay1lpXOs+9AAupOhgM3l/0hvIe c8YbnrO6k9DPoycHRYk2myjummIQRwOIxoIEBp92PqflPs7hCFlDBea+OeHsjMjhXi5X jwxbqwmVLRpPam/a9Y6WmsWYBtk69dvdHf6hgoDAOpu3VkBBa02ZTGwjntu8fyC05myj uiew== X-Gm-Message-State: AOAM533tbGV5Nl0pQXFwSYL69Q0TqxehaHGo+K/njHlAeqx+b7jU2vMP Gm7V1x/IxHd2GobDrIvLqp9IDQcNHWJyIw== X-Google-Smtp-Source: ABdhPJzyk3/6T2KTl3Q2oxAZNwgaIDL+ylwu4Jhi1U3VGe0zniFZfT/tDO/a8nD10ys8oqpnYWsUpw== X-Received: by 2002:a63:1b5c:: with SMTP id b28mr9670244pgm.186.1616710345290; Thu, 25 Mar 2021 15:12:25 -0700 (PDT) Received: from localhost (2001-44b8-111e-5c00-5199-f2bf-3cbb-22e6.static.ipv6.internode.on.net. [2001:44b8:111e:5c00:5199:f2bf:3cbb:22e6]) by smtp.gmail.com with ESMTPSA id w37sm6555685pgl.13.2021.03.25.15.12.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Mar 2021 15:12:24 -0700 (PDT) From: Daniel Axtens To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v2 06/15] powerpc/align: Don't use __get_user_instr() on kernel addresses In-Reply-To: References: Date: Fri, 26 Mar 2021 09:12:21 +1100 Message-ID: <877dlukhmi.fsf@dja-thinkpad.axtens.net> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christophe Leroy writes: > In the old days, when we didn't have kernel userspace access > protection and had set_fs(), it was wise to use __get_user() > and friends to read kernel memory. > > Nowadays, get_user() is granting userspace access and is exclusively > for userspace access. > > In alignment exception handler, use probe_kernel_read_inst() > instead of __get_user_instr() for reading instructions in kernel. > > This will allow to remove the is_kernel_addr() check in > __get/put_user() in a following patch. > Looks good to me! Reviewed-by: Daniel Axtens Kind regards, Daniel > Signed-off-by: Christophe Leroy > --- > arch/powerpc/kernel/align.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c > index c4d7b445b459..8d4c7af262e2 100644 > --- a/arch/powerpc/kernel/align.c > +++ b/arch/powerpc/kernel/align.c > @@ -310,7 +310,11 @@ int fix_alignment(struct pt_regs *regs) > */ > CHECK_FULL_REGS(regs); > > - if (unlikely(__get_user_instr(instr, (void __user *)regs->nip))) > + if (is_kernel_addr(regs->nip)) > + r = probe_kernel_read_inst(&instr, (void *)regs->nip); > + else > + r = __get_user_instr(instr, (void __user *)regs->nip); > + if (unlikely(r)) > return -EFAULT; > if ((regs->msr & MSR_LE) != (MSR_KERNEL & MSR_LE)) { > /* We don't handle PPC little-endian any more... */ > -- > 2.25.0