From patchwork Wed Jun 24 17:52:39 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 11624025 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 10ACE1392 for ; Wed, 24 Jun 2020 18:03:04 +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 DABF6206EB for ; Wed, 24 Jun 2020 18:03:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="m6HTzXuV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DABF6206EB 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+patchwork-linux-arm=patchwork.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: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=/A2OnGQO/TUvWMLJXm1A49cMjt0qLDoXTj9eG7jKYz8=; b=m6HTzXuVCDpIRDjvN78JSAVMU 0uCSqfvriogzqGm1FmeFjyu/V2Rd9PFQ3n3uXmcBKElyX5lFeuePwqsYdPgPjt78c7Rwr3oo101Zt 0YFdNwuJlJ1EHTJQDv1HSKZ8qPufHpboFe4qbT5gGVHhB1ttTDBpZDRMVpjPP6vZmxIdhyawz319T FjPqdm4KOK1HzXSc1UA8YW2tlhnmfXnoq69ee4u0xWIU3qj2YLpJ3EijHRuCXRYMIaxB8P1dNy2Rt Q8NU1Xc07Remn7of0y71mKcqbxkTu9Wb8sQL6KstJMlo+PBJvSJ7c4u6ONgrMy0jjRrnD2Ym0mxv1 PIIsoqLBQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo9hA-0008S0-MT; Wed, 24 Jun 2020 18:00:24 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo9aa-0004LN-1l for linux-arm-kernel@lists.infradead.org; Wed, 24 Jun 2020 17:53:37 +0000 Received: from localhost.localdomain (unknown [2.26.170.173]) (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 A9D472078E; Wed, 24 Jun 2020 17:53:32 +0000 (UTC) From: Catalin Marinas To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 20/25] fs: Handle intra-page faults in copy_mount_options() Date: Wed, 24 Jun 2020 18:52:39 +0100 Message-Id: <20200624175244.25837-21-catalin.marinas@arm.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200624175244.25837-1-catalin.marinas@arm.com> References: <20200624175244.25837-1-catalin.marinas@arm.com> MIME-Version: 1.0 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -5.0 (-----) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-5.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at https://www.dnswl.org/, high trust [198.145.29.99 listed in list.dnswl.org] 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail domains are different 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 , Andrew Morton , Vincenzo Frascino , Will Deacon , Dave P Martin Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.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 f30ed401cc6d..5b6a9c459674 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 size, left; if (!data) return NULL; @@ -3085,12 +3085,30 @@ 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;