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=-8.7 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 58249C04A6B for ; Wed, 8 May 2019 08:34:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2743421479 for ; Wed, 8 May 2019 08:34:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="IBeZgb+5"; dkim=fail reason="key not found in DNS" (0-bit key) header.d=codeaurora.org header.i=@codeaurora.org header.b="OLIvWECN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726771AbfEHIeS (ORCPT ); Wed, 8 May 2019 04:34:18 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:48558 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726481AbfEHIeS (ORCPT ); Wed, 8 May 2019 04:34:18 -0400 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 0582C60D35; Wed, 8 May 2019 08:34:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1557304457; bh=mDhuWudJppV+tmXjscDKqdwNpRqZ0VH+uYhZq8ihmDo=; h=From:To:Cc:Subject:Date:From; b=IBeZgb+5WCYEaQG9Gm5AujgPNZ8sqb1PsDyN3WPBvSp5VAosXWuzOt4zKoDqF0CiF dkEsICItQb9JjMmpZPj9/ZfbV2q7ing/3leaTrdRaAqEsq7Y9E8y4BODfqTWI8GITW W7XoRp6CfJKgGrOpPMMkojYSFy6Og8XyyGo8Opdg= Received: from codeaurora.org (blr-c-bdr-fw-01_globalnat_allzones-outside.qualcomm.com [103.229.19.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: stummala@smtp.codeaurora.org) by smtp.codeaurora.org (Postfix) with ESMTPSA id 87E2B60850; Wed, 8 May 2019 08:34:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=codeaurora.org; s=default; t=1557304456; bh=mDhuWudJppV+tmXjscDKqdwNpRqZ0VH+uYhZq8ihmDo=; h=From:To:Cc:Subject:Date:From; b=OLIvWECNUQ1mm8tprveMc+0l/bj3J6y5R5U2EhfVH3PR6wfbZTuG+mu32Z31RyYC6 iWyQJJbny2xy11JtRbqhVazxy3BiYz/+tcymHbCPJbtaXmwpToeSmBfZWeykTzXJLs 6iPisyyQAAUi2ma7STpMt9zel+FJJ+P6A7I6VQpM= DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 87E2B60850 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=stummala@codeaurora.org From: Sahitya Tummala To: Theodore Ts'o , Andreas Dilger , linux-ext4@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Sahitya Tummala Subject: [PATCH v2] ext4: fix use-after-free in dx_release() Date: Wed, 8 May 2019 14:04:03 +0530 Message-Id: <1557304443-18653-1-git-send-email-stummala@codeaurora.org> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- v2: add a comment in dx_release() fs/ext4/namei.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 980166a..5d9ffa8 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -871,12 +871,15 @@ static void dx_release(struct dx_frame *frames) { 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); -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.