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=-13.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,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 847A1C43613 for ; Thu, 20 Jun 2019 18:18:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6430B2089C for ; Thu, 20 Jun 2019 18:18:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561054739; bh=GOp3NByKc6r9Ck4fPiuEBrX64/JzIwN9Krtx+Ulfws8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=sA/Zzazwz4mGXIO6uQt46szzS2Vk00+FxPSDmL1gtZDOv4RO73kquO3rw+G8sBgwc L6QkgqriCZs5LaPNWp3nIQx58zWBWKu/WCAIBnaUcGAcgWlfQgracaNtgW4Nkyv3FO zcjGoz+RUIvyaSnV3y5kEHuUddRMUGKB1XgYdZfM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729669AbfFTSPt (ORCPT ); Thu, 20 Jun 2019 14:15:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:44718 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729654AbfFTSPq (ORCPT ); Thu, 20 Jun 2019 14:15:46 -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 AAD9121530; Thu, 20 Jun 2019 18:15:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561054545; bh=GOp3NByKc6r9Ck4fPiuEBrX64/JzIwN9Krtx+Ulfws8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NdbKzw7eV6BxiPEy95C9QfJi9htBtukmeTHJ1XlE8ifzopVRtx7Qw2tfEFzUEKiGK c5rthQWOCXnoUVifQZEpW4+LEea05SwMsFmTjeLPmTkWNvKSHt/XEoYoAZsr7GaEg3 Rb9R0aBXlR8qUmLM14gH9xcGlif66xL0OdJLjmOA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sahitya Tummala , Christoph Hellwig , Sasha Levin Subject: [PATCH 5.1 65/98] configfs: Fix use-after-free when accessing sd->s_dentry Date: Thu, 20 Jun 2019 19:57:32 +0200 Message-Id: <20190620174352.391036480@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190620174349.443386789@linuxfoundation.org> References: <20190620174349.443386789@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 [ Upstream commit f6122ed2a4f9c9c1c073ddf6308d1b2ac10e0781 ] In the vfs_statx() context, during path lookup, the dentry gets added to sd->s_dentry via configfs_attach_attr(). In the end, vfs_statx() kills the dentry by calling path_put(), which invokes configfs_d_iput(). Ideally, this dentry must be removed from sd->s_dentry but it doesn't if the sd->s_count >= 3. As a result, sd->s_dentry is holding reference to a stale dentry pointer whose memory is already freed up. This results in use-after-free issue, when this stale sd->s_dentry is accessed later in configfs_readdir() path. This issue can be easily reproduced, by running the LTP test case - sh fs_racer_file_list.sh /config (https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/fs/racer/fs_racer_file_list.sh) Fixes: 76ae281f6307 ('configfs: fix race between dentry put and lookup') Signed-off-by: Sahitya Tummala Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin --- fs/configfs/dir.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 920d350df37b..809c1edffbaf 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -58,15 +58,13 @@ static void configfs_d_iput(struct dentry * dentry, if (sd) { /* Coordinate with configfs_readdir */ spin_lock(&configfs_dirent_lock); - /* Coordinate with configfs_attach_attr where will increase - * sd->s_count and update sd->s_dentry to new allocated one. - * Only set sd->dentry to null when this dentry is the only - * sd owner. - * If not do so, configfs_d_iput may run just after - * configfs_attach_attr and set sd->s_dentry to null - * even it's still in use. + /* + * Set sd->s_dentry to null only when this dentry is the one + * that is going to be killed. Otherwise configfs_d_iput may + * run just after configfs_attach_attr and set sd->s_dentry to + * NULL even it's still in use. */ - if (atomic_read(&sd->s_count) <= 2) + if (sd->s_dentry == dentry) sd->s_dentry = NULL; spin_unlock(&configfs_dirent_lock); -- 2.20.1