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=-13.8 required=3.0 tests=BAYES_00, 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 D25C5C433E0 for ; Thu, 21 Jan 2021 16:58:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 812A323A51 for ; Thu, 21 Jan 2021 16:58:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731903AbhAUQ56 (ORCPT ); Thu, 21 Jan 2021 11:57:58 -0500 Received: from foss.arm.com ([217.140.110.172]:39930 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387725AbhAUPu3 (ORCPT ); Thu, 21 Jan 2021 10:50:29 -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 3F9A111D4; Thu, 21 Jan 2021 07:49:43 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.35.62]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 519AD3F68F; Thu, 21 Jan 2021 07:49:41 -0800 (PST) Date: Thu, 21 Jan 2021 15:49:38 +0000 From: Mark Rutland To: Vincenzo Frascino Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Andrey Konovalov , Leon Romanovsky , Alexander Potapenko , Catalin Marinas , Andrey Ryabinin , Will Deacon , Dmitry Vyukov , Ard Biesheuvel Subject: Re: [PATCH v2 1/2] arm64: Fix kernel address detection of __is_lm_address() Message-ID: <20210121154938.GJ48431@C02TD0UTHF1T.local> References: <20210121131956.23246-1-vincenzo.frascino@arm.com> <20210121131956.23246-2-vincenzo.frascino@arm.com> <20210121151206.GI48431@C02TD0UTHF1T.local> <95727b4c-4578-6eb5-b518-208482e8ba62@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <95727b4c-4578-6eb5-b518-208482e8ba62@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 21, 2021 at 03:30:51PM +0000, Vincenzo Frascino wrote: > On 1/21/21 3:12 PM, Mark Rutland wrote: > > On Thu, Jan 21, 2021 at 01:19:55PM +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). > > > > When it was added, __is_lm_address() was intended to distinguish valid > > kernel virtual addresses (i.e. those in the TTBR1 address range), and > > wasn't intended to do anything for addresses outside of this range. See > > commit: > > > > ec6d06efb0bac6cd ("arm64: Add support for CONFIG_DEBUG_VIRTUAL") > > > > ... where it simply tests a bit. > > > > So I believe that it's working as intended (though this is poorly > > documented), but I think you're saying that usage isn't aligned with > > that intent. Given that, I'm not sure the fixes tag is right; I think it > > has never had the semantic you're after. > > > I did not do much thinking on the intended semantics. I based my interpretation > on what you are saying (the usage is not aligned with the intent). Based on what > you are are saying, I will change the patch description removing the "Fix" term. Thanks! I assume that also means removing the fixes tag. > > I had thought the same was true for virt_addr_valid(), and that wasn't > > expected to be called for VAs outside of the kernel VA range. Is it > > actually safe to call that with NULL on other architectures? > > I am not sure on this, did not do any testing outside of arm64. I think it'd be worth checking, if we're going to use this in common code. > > I wonder if it's worth virt_addr_valid() having an explicit check for > > the kernel VA range, instead. > > I have no strong opinion either way even if personally I feel that modifying > __is_lm_address() is more clear. Feel free to propose something. Sure; I'm happy for it to live within __is_lm_address() if that's simpler overall, given it doesn't look like it's making that more complex or expensive. > >> Fix the detection checking that it's actually a kernel address starting > >> at PAGE_OFFSET. > >> > >> Fixes: f4693c2716b35 ("arm64: mm: extend linear region for 52-bit VA configurations") > >> Cc: Catalin Marinas > >> Cc: Will Deacon > >> Suggested-by: Catalin Marinas > >> Signed-off-by: Vincenzo Frascino > >> --- > >> arch/arm64/include/asm/memory.h | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > >> index 18fce223b67b..e04ac898ffe4 100644 > >> --- a/arch/arm64/include/asm/memory.h > >> +++ b/arch/arm64/include/asm/memory.h > >> @@ -249,7 +249,7 @@ static inline const void *__tag_set(const void *addr, u8 tag) > >> /* > >> * The linear kernel range starts at the bottom of the virtual address space. > >> */ > >> -#define __is_lm_address(addr) (((u64)(addr) & ~PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) > >> +#define __is_lm_address(addr) (((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) > > > > If we're going to make this stronger, can we please expand the comment > > with the intended semantic? Otherwise we're liable to break this in > > future. > > Based on your reply on the above matter, if you agree, I am happy to extend the > comment. Works for me; how about: /* * Check whether an arbitrary address is within the linear map, which * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the * kernel's TTBR1 address range. */ ... with "arbitrary" being the key word. Thanks, Mark. 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=-13.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CA3F3C433E0 for ; Thu, 21 Jan 2021 15:51:34 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 7D7EC22C7B for ; Thu, 21 Jan 2021 15:51:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D7EC22C7B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Eb6aPffmsshlOlB+ci8lrfU+SIlFl/mPkYtlAfJIjrE=; b=z7bgjqG59uFG5JJDYvkBJdi8U 7fZ/4p7YNbohw8xkPkiYzWTuIvD2ZNZEPPfOzzYBRKvEYtCO0Uh4QvhTWrdjnDQKkgugoo6QrXve5 XT85V9cTtqk6aStIWaxOQ4jL2gBBZQmcup4306JZhRX/4jK07PRHjG5tbqzrATJ8ARlsSQTp++3Oj HS39W2LwUypK2xxxurFB9HiorcM/Fk+NfMytQKvvqnZjF/bWNQMOPxD2cwi3OEDbUKVGWg5NMzTYW PGokWSrQZOd0Qu2xJZQMYBOTGCwyXTGNbR5OBXZxotddbs0OdnhjonWmrGL792K51j3V3pk2JA4Ja 7gdFMCUNg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cDT-0002l1-CZ; Thu, 21 Jan 2021 15:49:47 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2cDQ-0002kW-Ik for linux-arm-kernel@lists.infradead.org; Thu, 21 Jan 2021 15:49:45 +0000 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 3F9A111D4; Thu, 21 Jan 2021 07:49:43 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.35.62]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 519AD3F68F; Thu, 21 Jan 2021 07:49:41 -0800 (PST) Date: Thu, 21 Jan 2021 15:49:38 +0000 From: Mark Rutland To: Vincenzo Frascino Subject: Re: [PATCH v2 1/2] arm64: Fix kernel address detection of __is_lm_address() Message-ID: <20210121154938.GJ48431@C02TD0UTHF1T.local> References: <20210121131956.23246-1-vincenzo.frascino@arm.com> <20210121131956.23246-2-vincenzo.frascino@arm.com> <20210121151206.GI48431@C02TD0UTHF1T.local> <95727b4c-4578-6eb5-b518-208482e8ba62@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <95727b4c-4578-6eb5-b518-208482e8ba62@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210121_104944_720213_07E4F0F1 X-CRM114-Status: GOOD ( 36.68 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrey Konovalov , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Leon Romanovsky , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Andrey Ryabinin , Will Deacon , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jan 21, 2021 at 03:30:51PM +0000, Vincenzo Frascino wrote: > On 1/21/21 3:12 PM, Mark Rutland wrote: > > On Thu, Jan 21, 2021 at 01:19:55PM +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). > > > > When it was added, __is_lm_address() was intended to distinguish valid > > kernel virtual addresses (i.e. those in the TTBR1 address range), and > > wasn't intended to do anything for addresses outside of this range. See > > commit: > > > > ec6d06efb0bac6cd ("arm64: Add support for CONFIG_DEBUG_VIRTUAL") > > > > ... where it simply tests a bit. > > > > So I believe that it's working as intended (though this is poorly > > documented), but I think you're saying that usage isn't aligned with > > that intent. Given that, I'm not sure the fixes tag is right; I think it > > has never had the semantic you're after. > > > I did not do much thinking on the intended semantics. I based my interpretation > on what you are saying (the usage is not aligned with the intent). Based on what > you are are saying, I will change the patch description removing the "Fix" term. Thanks! I assume that also means removing the fixes tag. > > I had thought the same was true for virt_addr_valid(), and that wasn't > > expected to be called for VAs outside of the kernel VA range. Is it > > actually safe to call that with NULL on other architectures? > > I am not sure on this, did not do any testing outside of arm64. I think it'd be worth checking, if we're going to use this in common code. > > I wonder if it's worth virt_addr_valid() having an explicit check for > > the kernel VA range, instead. > > I have no strong opinion either way even if personally I feel that modifying > __is_lm_address() is more clear. Feel free to propose something. Sure; I'm happy for it to live within __is_lm_address() if that's simpler overall, given it doesn't look like it's making that more complex or expensive. > >> Fix the detection checking that it's actually a kernel address starting > >> at PAGE_OFFSET. > >> > >> Fixes: f4693c2716b35 ("arm64: mm: extend linear region for 52-bit VA configurations") > >> Cc: Catalin Marinas > >> Cc: Will Deacon > >> Suggested-by: Catalin Marinas > >> Signed-off-by: Vincenzo Frascino > >> --- > >> arch/arm64/include/asm/memory.h | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > >> index 18fce223b67b..e04ac898ffe4 100644 > >> --- a/arch/arm64/include/asm/memory.h > >> +++ b/arch/arm64/include/asm/memory.h > >> @@ -249,7 +249,7 @@ static inline const void *__tag_set(const void *addr, u8 tag) > >> /* > >> * The linear kernel range starts at the bottom of the virtual address space. > >> */ > >> -#define __is_lm_address(addr) (((u64)(addr) & ~PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) > >> +#define __is_lm_address(addr) (((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) > > > > If we're going to make this stronger, can we please expand the comment > > with the intended semantic? Otherwise we're liable to break this in > > future. > > Based on your reply on the above matter, if you agree, I am happy to extend the > comment. Works for me; how about: /* * Check whether an arbitrary address is within the linear map, which * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the * kernel's TTBR1 address range. */ ... with "arbitrary" being the key word. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel