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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 28DD4C433E1 for ; Thu, 18 Jun 2020 01:57:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0103A21924 for ; Thu, 18 Jun 2020 01:57:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592445424; bh=QgJqeKVZ+fjCXw8+dUiiojzmxkkV0/sy5VDLp1bn+Sg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=hAI3l+M+GjVtaBDzHodKXaTdKQJhqkubrs4DNzne7IVz2gXh52DvcuGiOeGA764Dw M2CPBVo7fAdSzpYzIvCd0E0ezoc8KHqF+Kyo587Vp4oQCd3v0CfUGTrArCJ6nU+9oH GcFfx6kWHK0cMzUaBf3mtWpP9aNXOkEgvShLO888= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731388AbgFRBZP (ORCPT ); Wed, 17 Jun 2020 21:25:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:60342 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731381AbgFRBZO (ORCPT ); Wed, 17 Jun 2020 21:25:14 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 AFEEC21D80; Thu, 18 Jun 2020 01:25:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592443514; bh=QgJqeKVZ+fjCXw8+dUiiojzmxkkV0/sy5VDLp1bn+Sg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=t21GHi9/J5gRnmGqOd7HQHQGAkBuL9m4SVGj31NA/Qg0C/46xlTb4P3u8T4k/PI+I TWHv7OYskbfcbkFg9frzz2ZkUbJ5HG/2Y2M485KuS9HVWh9ytlCdyOamUYwaF7R+zP 4qb6fu7yBpOYbD98XCcRVtXlN6ov86nubsw1F/qk= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Miklos Szeredi , Sasha Levin , linux-unionfs@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 138/172] ovl: verify permissions in ovl_path_open() Date: Wed, 17 Jun 2020 21:21:44 -0400 Message-Id: <20200618012218.607130-138-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200618012218.607130-1-sashal@kernel.org> References: <20200618012218.607130-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-unionfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org From: Miklos Szeredi [ Upstream commit 56230d956739b9cb1cbde439d76227d77979a04d ] Check permission before opening a real file. ovl_path_open() is used by readdir and copy-up routines. ovl_permission() theoretically already checked copy up permissions, but it doesn't hurt to re-do these checks during the actual copy-up. For directory reading ovl_permission() only checks access to topmost underlying layer. Readdir on a merged directory accesses layers below the topmost one as well. Permission wasn't checked for these layers. Note: modifying ovl_permission() to perform this check would be far more complex and hence more bug prone. The result is less precise permissions returned in access(2). If this turns out to be an issue, we can revisit this bug. Signed-off-by: Miklos Szeredi Signed-off-by: Sasha Levin --- fs/overlayfs/util.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index db8bdb29b320..afbc6a97da2a 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -479,7 +479,32 @@ bool ovl_is_whiteout(struct dentry *dentry) struct file *ovl_path_open(struct path *path, int flags) { - return dentry_open(path, flags | O_NOATIME, current_cred()); + struct inode *inode = d_inode(path->dentry); + int err, acc_mode; + + if (flags & ~(O_ACCMODE | O_LARGEFILE)) + BUG(); + + switch (flags & O_ACCMODE) { + case O_RDONLY: + acc_mode = MAY_READ; + break; + case O_WRONLY: + acc_mode = MAY_WRITE; + break; + default: + BUG(); + } + + err = inode_permission(inode, acc_mode | MAY_OPEN); + if (err) + return ERR_PTR(err); + + /* O_NOATIME is an optimization, don't fail if not permitted */ + if (inode_owner_or_capable(inode)) + flags |= O_NOATIME; + + return dentry_open(path, flags, current_cred()); } /* Caller should hold ovl_inode->lock */ -- 2.25.1