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=-14.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,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 F2257C28CC5 for ; Sat, 8 Jun 2019 11:50:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CB529216F4 for ; Sat, 8 Jun 2019 11:50:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559994634; bh=YntNBn8zkYQ2utLEVUx+pG7XxnLayxLCz5AZlQ+gEo0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=0kOM5VqDEeqgTl7efHPXM6t/XKy+RbpFM02hRsDPtfS0tnlApob0X1czot/t0i1DM ZwM2QAgk4lqaSptiRWRHlmgW/TagMIOpblfVffkX9E0M62gEDcZu5FJ318RQ4Hp+Eb FiGYlqARrT/y1SQk2/gV164U3q7+xyHkfknO2ZP0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729658AbfFHLs3 (ORCPT ); Sat, 8 Jun 2019 07:48:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:37162 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727675AbfFHLsZ (ORCPT ); Sat, 8 Jun 2019 07:48:25 -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 7B0D1216FD; Sat, 8 Jun 2019 11:48:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559994505; bh=YntNBn8zkYQ2utLEVUx+pG7XxnLayxLCz5AZlQ+gEo0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=V9yEWxTANQ5dfO35IWHX2WiHLl/V/evxIBlDCpKEH2QCCqYDb2vdSKF+yJPZNbumk fQHtnUHBIlxVPZ5DVaJ3WBFxsivuQme/mOuMRwFV9REPW+coWfFK6D7i2jjEf6Tswr i9peTA/GaY+V9VTU16czge6onRS5G3HODnhEFId8= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sahitya Tummala , Christoph Hellwig , Sasha Levin Subject: [PATCH AUTOSEL 4.9 10/20] configfs: Fix use-after-free when accessing sd->s_dentry Date: Sat, 8 Jun 2019 07:47:46 -0400 Message-Id: <20190608114756.9742-10-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190608114756.9742-1-sashal@kernel.org> References: <20190608114756.9742-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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 [ 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 d2a1a79fa324..4930a3a211f3 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