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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 267D1C04AAC for ; Mon, 20 May 2019 12:41:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F09F320645 for ; Mon, 20 May 2019 12:41:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558356116; bh=Y+8Y21qUCRMYjTUDfur/iQJvKkhuVBO32bLyVOUL494=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=jpdH3jk0mRb2yOI9Omhhe2742AGekFwTQXSBKgWx8s4ZAmcr+ZB6VRr7GqJCuMv9a pbkMo/dSFoY3uXUky28EVXr82jr0WOgJDomVe4YL5XVkFsVS/t1tp7NeaKsWwxvA9g TEG4fu7cUxt2ni2c9ZpZ5WbeiA9TNHtPdOlPm0eY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390211AbfETMbA (ORCPT ); Mon, 20 May 2019 08:31:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:47274 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390182AbfETMax (ORCPT ); Mon, 20 May 2019 08:30:53 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 90D2820645; Mon, 20 May 2019 12:30:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558355453; bh=Y+8Y21qUCRMYjTUDfur/iQJvKkhuVBO32bLyVOUL494=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QrPjDI/oK2v7NRFVJJRMXMzJ8o203Xm0bPyEguDExk1DLiz/rOoGdoN9KCjyyo3Ds XrYWQH3OlANvLiWot0sTkJ9KBnpsFCr5rMHf5mCvBGEezEg7batgp9Nr+sysZWvCq6 ATARAJPPqw781x7iVqpeK2qhN3pp8QazdpCaFSMw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sahitya Tummala , Theodore Tso , Andreas Dilger , stable@kernel.org Subject: [PATCH 5.0 104/123] ext4: fix use-after-free in dx_release() Date: Mon, 20 May 2019 14:14:44 +0200 Message-Id: <20190520115251.954691616@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190520115245.439864225@linuxfoundation.org> References: <20190520115245.439864225@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sahitya Tummala commit 08fc98a4d6424af66eb3ac4e2cedd2fc927ed436 upstream. The buffer_head (frames[0].bh) and it's corresping page can be potentially free'd once brelse() is done inside the for loop but before the for loop exits in dx_release(). It can be free'd in another context, when the page cache is flushed via drop_caches_sysctl_handler(). This results into below data abort when accessing info->indirect_levels in dx_release(). Unable to handle kernel paging request at virtual address ffffffc17ac3e01e Call trace: dx_release+0x70/0x90 ext4_htree_fill_tree+0x2d4/0x300 ext4_readdir+0x244/0x6f8 iterate_dir+0xbc/0x160 SyS_getdents64+0x94/0x174 Signed-off-by: Sahitya Tummala Signed-off-by: Theodore Ts'o Reviewed-by: Andreas Dilger Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/ext4/namei.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -871,12 +871,15 @@ static void dx_release(struct dx_frame * { struct dx_root_info *info; int i; + unsigned int indirect_levels; if (frames[0].bh == NULL) return; info = &((struct dx_root *)frames[0].bh->b_data)->info; - for (i = 0; i <= info->indirect_levels; i++) { + /* save local copy, "info" may be freed after brelse() */ + indirect_levels = info->indirect_levels; + for (i = 0; i <= indirect_levels; i++) { if (frames[i].bh == NULL) break; brelse(frames[i].bh);