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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 721DAC433E0 for ; Tue, 26 Jan 2021 12:11:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3AB8220637 for ; Tue, 26 Jan 2021 12:11:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392439AbhAZMLW (ORCPT ); Tue, 26 Jan 2021 07:11:22 -0500 Received: from foss.arm.com ([217.140.110.172]:36500 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392305AbhAZMKv (ORCPT ); Tue, 26 Jan 2021 07:10:51 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 21C2B101E; Tue, 26 Jan 2021 04:10:06 -0800 (PST) Received: from [10.37.12.25] (unknown [10.37.12.25]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D90C53F66B; Tue, 26 Jan 2021 04:10:03 -0800 (PST) Subject: Re: [PATCH v4 1/3] arm64: Improve kernel address detection of __is_lm_address() To: Catalin Marinas 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 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> <20210125175630.GK25360@gaia> <62348cb4-0b2e-e17a-d930-8d41dc4200d3@arm.com> <20210126120754.GB20158@gaia> From: Vincenzo Frascino Message-ID: Date: Tue, 26 Jan 2021 12:13:57 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210126120754.GB20158@gaia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/26/21 12:07 PM, Catalin Marinas wrote: > On Tue, Jan 26, 2021 at 11:58:13AM +0000, Vincenzo Frascino wrote: >> On 1/25/21 5:56 PM, Catalin Marinas wrote: >>> 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. >> >> Then call it preparatory patch ;) > > It's preparatory only for the stable backports, not for current > mainline. But I'd rather change the upstream patch when backporting to > apply cleanly, no need for a preparatory stable patch. > Thanks for the clarification. -- Regards, Vincenzo