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=-8.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 38106C433E0 for ; Fri, 29 May 2020 04:22:29 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 A7C392074D for ; Fri, 29 May 2020 04:22:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A7C392074D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49YBHQ1Fb6zDqbp for ; Fri, 29 May 2020 14:22:26 +1000 (AEST) Received: from ozlabs.org (bilbo.ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 49YBF42xRYzDqZN for ; Fri, 29 May 2020 14:20:24 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Received: by ozlabs.org (Postfix, from userid 1034) id 49YBF35KWQz9sSr; Fri, 29 May 2020 14:20:23 +1000 (AEST) X-powerpc-patch-notification: thanks X-powerpc-patch-commit: 999a22890cb183b918e4372395d24426a755cef2 In-Reply-To: <36e43241c7f043a24b5069e78c6a7edd11043be5.1585898438.git.christophe.leroy@c-s.fr> To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , airlied@linux.ie, daniel@ffwll.ch, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org, keescook@chromium.org, hpa@zytor.com From: Michael Ellerman Subject: Re: [PATCH v2 1/5] uaccess: Add user_read_access_begin/end and user_write_access_begin/end Message-Id: <49YBF35KWQz9sSr@ozlabs.org> Date: Fri, 29 May 2020 14:20:23 +1000 (AEST) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, linux-mm@kvack.org, intel-gfx@lists.freedesktop.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, 2020-04-03 at 07:20:50 UTC, Christophe Leroy wrote: > Some architectures like powerpc64 have the capability to separate > read access and write access protection. > For get_user() and copy_from_user(), powerpc64 only open read access. > For put_user() and copy_to_user(), powerpc64 only open write access. > But when using unsafe_get_user() or unsafe_put_user(), > user_access_begin open both read and write. > > Other architectures like powerpc book3s 32 bits only allow write > access protection. And on this architecture protection is an heavy > operation as it requires locking/unlocking per segment of 256Mbytes. > On those architecture it is therefore desirable to do the unlocking > only for write access. (Note that book3s/32 ranges from very old > powermac from the 90's with powerpc 601 processor, till modern > ADSL boxes with PowerQuicc II processors for instance so it > is still worth considering.) > > In order to avoid any risk based of hacking some variable parameters > passed to user_access_begin/end that would allow hacking and > leaving user access open or opening too much, it is preferable to > use dedicated static functions that can't be overridden. > > Add a user_read_access_begin and user_read_access_end to only open > read access. > > Add a user_write_access_begin and user_write_access_end to only open > write access. > > By default, when undefined, those new access helpers default on the > existing user_access_begin and user_access_end. > > Signed-off-by: Christophe Leroy > Reviewed-by: Kees Cook Applied to powerpc topic/uaccess, thanks. https://git.kernel.org/powerpc/c/999a22890cb183b918e4372395d24426a755cef2 cheers