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=-10.0 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 4B2C4C433E0 for ; Fri, 3 Jul 2020 15:38:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 119D821534 for ; Fri, 3 Jul 2020 15:38:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 119D821534 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 78F838D0083; Fri, 3 Jul 2020 11:38:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 719888D0074; Fri, 3 Jul 2020 11:38:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 544EA8D0083; Fri, 3 Jul 2020 11:38:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0176.hostedemail.com [216.40.44.176]) by kanga.kvack.org (Postfix) with ESMTP id 366388D0074 for ; Fri, 3 Jul 2020 11:38:14 -0400 (EDT) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E6D928248068 for ; Fri, 3 Jul 2020 15:38:13 +0000 (UTC) X-FDA: 76997170866.18.army55_0d0ae8226e93 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin18.hostedemail.com (Postfix) with ESMTP id B8D46100ED3BC for ; Fri, 3 Jul 2020 15:38:13 +0000 (UTC) X-HE-Tag: army55_0d0ae8226e93 X-Filterd-Recvd-Size: 3876 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Fri, 3 Jul 2020 15:38:13 +0000 (UTC) Received: from localhost.localdomain (unknown [95.146.230.158]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8F272215A4; Fri, 3 Jul 2020 15:38:10 +0000 (UTC) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Vincenzo Frascino , Szabolcs Nagy , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne , Andrew Morton , Alexander Viro Subject: [PATCH v6 21/26] fs: Handle intra-page faults in copy_mount_options() Date: Fri, 3 Jul 2020 16:37:13 +0100 Message-Id: <20200703153718.16973-22-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200703153718.16973-1-catalin.marinas@arm.com> References: <20200703153718.16973-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: B8D46100ED3BC X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 no size and 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() implementation performs two copy_from_user() passes, first to the end of the current page and the second to what's left in the subsequent page. On arm64 with MTE enabled, access to a user page may trigger a fault after part of the buffer in a page has been copied (when the user pointer tag, bits 56-59, no longer matches the allocation tag stored in memory). Allow copy_mount_options() to handle such intra-page faults by resorting to byte at a time copy in case of copy_from_user() failure. Note that copy_from_user() handles the zeroing of the kernel buffer in case of error. Signed-off-by: Catalin Marinas Cc: Alexander Viro --- Notes: v6: - Simplified logic to fall-back to byte-by-byte if the copy_from_user= () fails. =20 v4: - Rewrite to avoid arch_has_exact_copy_from_user() =20 New in v3. fs/namespace.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index f30ed401cc6d..163ac986dc2d 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3074,7 +3074,7 @@ static void shrink_submounts(struct mount *mnt) void *copy_mount_options(const void __user * data) { char *copy; - unsigned size; + unsigned left, offset; =20 if (!data) return NULL; @@ -3083,16 +3083,27 @@ void *copy_mount_options(const void __user * data= ) if (!copy) return ERR_PTR(-ENOMEM); =20 - size =3D PAGE_SIZE - offset_in_page(data); + left =3D copy_from_user(copy, data, PAGE_SIZE); =20 - if (copy_from_user(copy, data, size)) { + /* + * Not all architectures have an exact copy_form_user(). Resort to + * byte at a time. + */ + offset =3D PAGE_SIZE - left; + while (left) { + char c; + if (get_user(c, (const char __user *)data + offset)) + break; + copy[offset] =3D c; + left--; + offset++; + } + + if (left =3D=3D PAGE_SIZE) { kfree(copy); return ERR_PTR(-EFAULT); } - if (size !=3D PAGE_SIZE) { - if (copy_from_user(copy + size, data + size, PAGE_SIZE - size)) - memset(copy + size, 0, PAGE_SIZE - size); - } + return copy; } =20