Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86C0CC433EF for ; Wed, 24 Nov 2021 19:20:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244793AbhKXTXv (ORCPT ); Wed, 24 Nov 2021 14:23:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:56660 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243912AbhKXTXn (ORCPT ); Wed, 24 Nov 2021 14:23:43 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id CAA2460E05; Wed, 24 Nov 2021 19:20:31 +0000 (UTC) From: Catalin Marinas To: Linus Torvalds , Josef Bacik , David Sterba Cc: Andreas Gruenbacher , Al Viro , Andrew Morton , Will Deacon , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-btrfs@vger.kernel.org Subject: [PATCH 2/3] arm64: Add support for sub-page faults user probing Date: Wed, 24 Nov 2021 19:20:23 +0000 Message-Id: <20211124192024.2408218-3-catalin.marinas@arm.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20211124192024.2408218-1-catalin.marinas@arm.com> References: <20211124192024.2408218-1-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With MTE, even if the pte allows an access, a mismatched tag somewhere within a page can still cause a fault. Select ARCH_HAS_SUBPAGE_FAULTS if MTE is enabled and implement probe_user_writeable(). Signed-off-by: Catalin Marinas --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/uaccess.h | 33 ++++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c4207cf9bb17..dff89fd0d817 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1777,6 +1777,7 @@ config ARM64_MTE depends on AS_HAS_LSE_ATOMICS # Required for tag checking in the uaccess routines depends on ARM64_PAN + select ARCH_HAS_SUBPAGE_FAULTS select ARCH_USES_HIGH_VMA_FLAGS help Memory Tagging (part of the ARMv8.5 Extensions) provides diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 6e2e0b7031ab..4bf947e9f9bf 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -445,4 +445,37 @@ static inline int __copy_from_user_flushcache(void *dst, const void __user *src, } #endif +#ifdef CONFIG_ARCH_HAS_SUBPAGE_FAULTS +static inline size_t __mte_probe_user_range(const char __user *uaddr, + size_t size) +{ + const char __user *end = uaddr + size; + int err = 0; + char val; + + uaddr = PTR_ALIGN_DOWN(uaddr, MTE_GRANULE_SIZE); + while (uaddr < end) { + /* + * A read is sufficient for MTE, the caller should have probed + * for the pte write permission. + */ + __raw_get_user(val, uaddr, err); + if (err) + return end - uaddr; + uaddr += MTE_GRANULE_SIZE; + } + (void)val; + + return 0; +} + +static inline size_t probe_user_writable(const void __user *uaddr, + size_t size) +{ + if (!system_supports_mte()) + return 0; + return __mte_probe_user_range(uaddr, size); +} +#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */ + #endif /* __ASM_UACCESS_H */