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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 B932CC54FCC for ; Tue, 21 Apr 2020 14:27:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5A76C206B9 for ; Tue, 21 Apr 2020 14:27:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5A76C206B9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E47CA8E0019; Tue, 21 Apr 2020 10:26:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DFAC48E0003; Tue, 21 Apr 2020 10:26:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CC0F28E0019; Tue, 21 Apr 2020 10:26:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0070.hostedemail.com [216.40.44.70]) by kanga.kvack.org (Postfix) with ESMTP id B4D158E0003 for ; Tue, 21 Apr 2020 10:26:49 -0400 (EDT) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 77527181AEF07 for ; Tue, 21 Apr 2020 14:26:49 +0000 (UTC) X-FDA: 76732088538.09.club71_1e6fc95c75933 X-HE-Tag: club71_1e6fc95c75933 X-Filterd-Recvd-Size: 5090 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf37.hostedemail.com (Postfix) with ESMTP for ; Tue, 21 Apr 2020 14:26:49 +0000 (UTC) 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 A20A231B; Tue, 21 Apr 2020 07:26:48 -0700 (PDT) Received: from localhost.localdomain (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 038733F68F; Tue, 21 Apr 2020 07:26:46 -0700 (PDT) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Cc: Will Deacon , Vincenzo Frascino , Szabolcs Nagy , Richard Earnshaw , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne , linux-mm@kvack.org, linux-arch@vger.kernel.org, Alexander Viro Subject: [PATCH v3 20/23] fs: Allow copy_mount_options() to access user-space in a single pass Date: Tue, 21 Apr 2020 15:26:00 +0100 Message-Id: <20200421142603.3894-21-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200421142603.3894-1-catalin.marinas@arm.com> References: <20200421142603.3894-1-catalin.marinas@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The copy_mount_options() function takes a user pointer argument but not a size. It tries to read up to a PAGE_SIZE. However, copy_from_user() is not guaranteed to return all the accessible bytes if, for example, the access crosses a page boundary and gets a fault on the second page. To work around this, the current copy_mount_options() implementations performs to copy_from_user() passes, first to the end of the current page and the second to what's left in the subsequent page. Some architectures like arm64 can guarantee an exact copy_from_user() depending on the size (since the arch function performs some alignment on the source register). Introduce an arch_has_exact_copy_from_user() function and allow copy_mount_options() to perform the user access in a single pass. While this function is not on a critical path, the single-pass behaviour is required for arm64 MTE (memory tagging) support where a uaccess can trigger intra-page faults (tag not matching). With the current implementation, if this happens during the first page, the function will return -EFAULT. Signed-off-by: Catalin Marinas Cc: Alexander Viro Cc: Will Deacon --- Notes: New in v3. arch/arm64/include/asm/uaccess.h | 11 +++++++++++ fs/namespace.c | 7 +++++-- include/linux/uaccess.h | 8 ++++++++ 3 files changed, 24 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/ua= ccess.h index 32fc8061aa76..566da441eba2 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -416,6 +416,17 @@ extern unsigned long __must_check __arch_copy_in_use= r(void __user *to, const voi #define INLINE_COPY_TO_USER #define INLINE_COPY_FROM_USER =20 +static inline bool arch_has_exact_copy_from_user(unsigned long n) +{ + /* + * copy_from_user() aligns the source pointer if the size is greater + * than 15. Since all the loads are naturally aligned, they can only + * fail on the first byte. + */ + return n > 15; +} +#define arch_has_exact_copy_from_user + extern unsigned long __must_check __arch_clear_user(void __user *to, uns= igned long n); static inline unsigned long __must_check __clear_user(void __user *to, u= nsigned long n) { diff --git a/fs/namespace.c b/fs/namespace.c index a28e4db075ed..8febc50dfc5d 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3025,13 +3025,16 @@ void *copy_mount_options(const void __user * data= ) if (!copy) return ERR_PTR(-ENOMEM); =20 - size =3D PAGE_SIZE - offset_in_page(data); + size =3D PAGE_SIZE; + if (!arch_has_exact_copy_from_user(size)) + size -=3D offset_in_page(data); =20 - if (copy_from_user(copy, data, size)) { + if (copy_from_user(copy, data, size) =3D=3D size) { kfree(copy); return ERR_PTR(-EFAULT); } if (size !=3D PAGE_SIZE) { + WARN_ON(1); if (copy_from_user(copy + size, data + size, PAGE_SIZE - size)) memset(copy + size, 0, PAGE_SIZE - size); } diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 67f016010aad..00e097a9e8d6 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -152,6 +152,14 @@ copy_to_user(void __user *to, const void *from, unsi= gned long n) n =3D _copy_to_user(to, from, n); return n; } + +#ifndef arch_has_exact_copy_from_user +static inline bool arch_has_exact_copy_from_user(unsigned long n) +{ + return false; +} +#endif + #ifdef CONFIG_COMPAT static __always_inline unsigned long __must_check copy_in_user(void __user *to, const void __user *from, unsigned long n)