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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 623F5C433DF for ; Fri, 15 May 2020 17:22:15 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 E8E6620727 for ; Fri, 15 May 2020 17:22:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="RI81Jggp" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E8E6620727 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-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=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=c3OGnYv+A0fev65JclXJL/pbiZYQ9Yu9wuX7i9Uu3gY=; b=RI81JggpvoYLDS L/5qfCy5JhzA4AxbJF12+k8CmV2eBVoJKBeTOIwGziWxymfA5zJkRsiFBIpTja0yXvea/ZfvTJ/iz QqahMWqgxvrtDkwOmUown1ERDYTdXSrdEP2zjJN7SfwaD7LeXh9gNz3vaGHHG1nxCiUPAa48ZDf29 LsneAaE7ODbTh9xNr0nol6/ThM3Cv8q1/BSuzYQNeAZ+Ft5VbJ7eWU6pXl7FqacmBbWun46SDKI9c AT2UN/2YJimg4IagwtTaTzDszF+WE9UrqlVIUennrmjOtg8akLc3ejcCFOr2/dPpJNgebhY3pMg2f fK3j28q+SNW5RQpwtZtw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZe2I-00015S-FQ; Fri, 15 May 2020 17:22:14 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZdxD-0002VV-Lu for linux-arm-kernel@lists.infradead.org; Fri, 15 May 2020 17:17:01 +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 81FB81063; Fri, 15 May 2020 10:16:59 -0700 (PDT) Received: from localhost.localdomain (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D50F93F305; Fri, 15 May 2020 10:16:57 -0700 (PDT) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v4 19/26] fs: Handle intra-page faults in copy_mount_options() Date: Fri, 15 May 2020 18:16:05 +0100 Message-Id: <20200515171612.1020-20-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200515171612.1020-1-catalin.marinas@arm.com> References: <20200515171612.1020-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200515_101659_802235_9E088ED0 X-CRM114-Status: GOOD ( 16.20 ) 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: linux-arch@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Peter Collingbourne , linux-mm@kvack.org, Alexander Viro , Vincenzo Frascino , Will Deacon , Dave P Martin Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org The copy_mount_options() function takes a user pointer argument but no 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() 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 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 returning -EFAULT only if the first copy_from_user() has not copied any bytes. Signed-off-by: Catalin Marinas Cc: Alexander Viro Reviewed-by: Kevin Brodsky --- Notes: v4: - Rewrite to avoid arch_has_exact_copy_from_user() New in v3. fs/namespace.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index a28e4db075ed..70aa60ccce57 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -3016,7 +3016,7 @@ static void shrink_submounts(struct mount *mnt) void *copy_mount_options(const void __user * data) { char *copy; - unsigned size; + unsigned size, left; if (!data) return NULL; @@ -3027,12 +3027,30 @@ void *copy_mount_options(const void __user * data) size = PAGE_SIZE - offset_in_page(data); - if (copy_from_user(copy, data, size)) { + /* + * Attempt to copy to the end of the first user page. On success, + * left == 0, copy the rest from the second user page (if it is + * accessible). copy_from_user() will zero the part of the kernel + * buffer not copied into. + * + * On architectures with intra-page faults (arm64 with MTE), the read + * from the first page may fail after copying part of the user data + * (left > 0 && left < size). Do not attempt the second copy in this + * case as the end of the valid user buffer has already been reached. + * Ensure, however, that the second part of the kernel buffer is + * zeroed. + */ + left = copy_from_user(copy, data, size); + if (left == size) { kfree(copy); return ERR_PTR(-EFAULT); } if (size != PAGE_SIZE) { - if (copy_from_user(copy + size, data + size, PAGE_SIZE - size)) + if (left == 0) + /* return not relevant, just silence the compiler */ + left = copy_from_user(copy + size, data + size, + PAGE_SIZE - size); + else memset(copy + size, 0, PAGE_SIZE - size); } return copy; _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel