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 6C543C433E0 for ; Mon, 25 Jan 2021 17:58:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 38E3E22B3B for ; Mon, 25 Jan 2021 17:58:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731166AbhAYR6t (ORCPT ); Mon, 25 Jan 2021 12:58:49 -0500 Received: from mail.kernel.org ([198.145.29.99]:41864 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731354AbhAYR5Q (ORCPT ); Mon, 25 Jan 2021 12:57:16 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 426B622583; Mon, 25 Jan 2021 17:56:33 +0000 (UTC) Date: Mon, 25 Jan 2021 17:56:30 +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: <20210125175630.GK25360@gaia> References: <20210122155642.23187-1-vincenzo.frascino@arm.com> <20210122155642.23187-2-vincenzo.frascino@arm.com> <20210125130204.GA4565@C02TD0UTHF1T.local> <20210125145911.GG25360@gaia> <4bd1c01b-613c-787f-4363-c55a071f14ae@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4bd1c01b-613c-787f-4363-c55a071f14ae@arm.com> 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 04:09:57PM +0000, Vincenzo Frascino wrote: > On 1/25/21 2:59 PM, Catalin Marinas wrote: > > 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 > NULL address is considered valid. > > > > Ard's commit f4693c2716b3 ("arm64: mm: extend linear region for 52-bit > > VA configurations") changed the test to no longer rely on va_bits but > > did not change the broken semantics. > > > > If Ard's change plus the fix proposed in this test works on 5.4, I'd say > > we just merge this patch with the corresponding Cc stable and Fixes tags > > and tweak it slightly when doing the backports as it wouldn't apply > > cleanly. IOW, I wouldn't add another check to virt_addr_valid() as we > > did not need one prior to 5.4. > > Thank you for the detailed analysis. I checked on 5.4 and it seems that Ard > patch (not a clean backport) plus my proposed fix works correctly and solves the > issue. I didn't mean the backport of the whole commit f4693c2716b3 as it probably has other dependencies, just the __is_lm_address() change in that patch. > Tomorrow I will post a new version of the series that includes what you are > suggesting. Please post the __is_lm_address() fix separately from the kasan patches. I'll pick it up as a fix via the arm64 tree. The kasan change can go in 5.12 since it's not currently broken but I'll leave the decision with Andrey. -- Catalin