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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 9E94BC433E6 for ; Mon, 25 Jan 2021 15:29:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F08423132 for ; Mon, 25 Jan 2021 15:29:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730001AbhAYP3D (ORCPT ); Mon, 25 Jan 2021 10:29:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:60772 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729904AbhAYPAl (ORCPT ); Mon, 25 Jan 2021 10:00:41 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E1BA622ADF; Mon, 25 Jan 2021 14:59:14 +0000 (UTC) Date: Mon, 25 Jan 2021 14:59:12 +0000 From: Catalin Marinas To: Vincenzo Frascino Cc: Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Leon Romanovsky , Andrey Konovalov , Will Deacon , "Paul E . McKenney" , Naresh Kamboju Subject: Re: [PATCH v4 1/3] arm64: Improve kernel address detection of __is_lm_address() Message-ID: <20210125145911.GG25360@gaia> References: <20210122155642.23187-1-vincenzo.frascino@arm.com> <20210122155642.23187-2-vincenzo.frascino@arm.com> <20210125130204.GA4565@C02TD0UTHF1T.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 25, 2021 at 02:36:34PM +0000, Vincenzo Frascino wrote: > On 1/25/21 1:02 PM, Mark Rutland wrote: > > On Fri, Jan 22, 2021 at 03:56:40PM +0000, Vincenzo Frascino wrote: > >> Currently, the __is_lm_address() check just masks out the top 12 bits > >> of the address, but if they are 0, it still yields a true result. > >> This has as a side effect that virt_addr_valid() returns true even for > >> invalid virtual addresses (e.g. 0x0). > >> > >> Improve the detection checking that it's actually a kernel address > >> starting at PAGE_OFFSET. > >> > >> Cc: Catalin Marinas > >> Cc: Will Deacon > >> Suggested-by: Catalin Marinas > >> Reviewed-by: Catalin Marinas > >> Signed-off-by: Vincenzo Frascino > > > > Looking around, it seems that there are some existing uses of > > virt_addr_valid() that expect it to reject addresses outside of the > > TTBR1 range. For example, check_mem_type() in drivers/tee/optee/call.c. > > > > Given that, I think we need something that's easy to backport to stable. > > > > I agree, I started looking at it this morning and I found cases even in the main > allocators (slub and page_alloc) either then the one you mentioned. > > > This patch itself looks fine, but it's not going to backport very far, > > so I suspect we might need to write a preparatory patch that adds an > > explicit range check to virt_addr_valid() which can be trivially > > backported. > > > > I checked the old releases and I agree this is not back-portable as it stands. > I propose therefore to add a preparatory patch with the check below: > > #define __is_ttrb1_address(addr) ((u64)(addr) >= PAGE_OFFSET && \ > (u64)(addr) < PAGE_END) > > If it works for you I am happy to take care of it and post a new version of my > patches. I'm not entirely sure we need a preparatory patch. IIUC (it needs checking), virt_addr_valid() was fine until 5.4, broken by commit 14c127c957c1 ("arm64: mm: Flip kernel VA space"). Will addressed the flip case in 68dd8ef32162 ("arm64: memory: Fix virt_addr_valid() using __is_lm_address()") but this broke the