From patchwork Thu Sep 22 12:04:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Baokun Li X-Patchwork-Id: 1681068 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org (client-ip=2404:9400:2221:ea00::3; helo=gandalf.ozlabs.org; envelope-from=srs0=vn2e=zz=vger.kernel.org=linux-ext4-owner@ozlabs.org; receiver=) Received: from gandalf.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-384) server-digest SHA384) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4MYDG0394sz1yqL for ; Thu, 22 Sep 2022 21:54:00 +1000 (AEST) Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4MYDFx39ckz4xFs for ; Thu, 22 Sep 2022 21:53:57 +1000 (AEST) Received: by gandalf.ozlabs.org (Postfix) id 4MYDFx37mxz4xGN; Thu, 22 Sep 2022 21:53:57 +1000 (AEST) Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: gandalf.ozlabs.org; dmarc=fail (p=quarantine dis=none) header.from=huawei.com Authentication-Results: gandalf.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=2620:137:e000::1:20; helo=out1.vger.email; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Received: from out1.vger.email (out1.vger.email [IPv6:2620:137:e000::1:20]) by gandalf.ozlabs.org (Postfix) with ESMTP id 4MYDFx34GMz4xFs for ; Thu, 22 Sep 2022 21:53:57 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229585AbiIVLxx (ORCPT ); Thu, 22 Sep 2022 07:53:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230235AbiIVLxv (ORCPT ); Thu, 22 Sep 2022 07:53:51 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 426299752A; Thu, 22 Sep 2022 04:53:50 -0700 (PDT) Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4MYDCF4mg8zHp14; Thu, 22 Sep 2022 19:51:37 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Thu, 22 Sep 2022 19:53:47 +0800 From: Baokun Li To: CC: , , , , , , , , , , , , Subject: [PATCH v2] ext4: fix use-after-free in ext4_ext_shift_extents Date: Thu, 22 Sep 2022 20:04:34 +0800 Message-ID: <20220922120434.1294789-1-libaokun1@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org If the starting position of our insert range happens to be in the hole between the two ext4_extent_idx, because the lblk of the ext4_extent in the previous ext4_extent_idx is always less than the start, which leads to the "extent" variable access across the boundary, the following UAF is triggered: ================================================================== BUG: KASAN: use-after-free in ext4_ext_shift_extents+0x257/0x790 Read of size 4 at addr ffff88819807a008 by task fallocate/8010 CPU: 3 PID: 8010 Comm: fallocate Tainted: G E 5.10.0+ #492 Call Trace: dump_stack+0x7d/0xa3 print_address_description.constprop.0+0x1e/0x220 kasan_report.cold+0x67/0x7f ext4_ext_shift_extents+0x257/0x790 ext4_insert_range+0x5b6/0x700 ext4_fallocate+0x39e/0x3d0 vfs_fallocate+0x26f/0x470 ksys_fallocate+0x3a/0x70 __x64_sys_fallocate+0x4f/0x60 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 ================================================================== For right shifts, we can divide them into the following situations： 1. When the first ee_block of ext4_extent_idx is greater than or equal to start, make right shifts directly from the first ee_block. 1) If it is greater than start, we need to continue searching in the previous ext4_extent_idx. 2) If it is equal to start, we can exit the loop (iterator=NULL). 2. When the first ee_block of ext4_extent_idx is less than start, then traverse from the last extent to find the first extent whose ee_block is less than start. 1) If extent is still the last extent after traversal, it means that the last ee_block of ext4_extent_idx is less than start, that is, start is located in the hole between idx and (idx+1), so we can exit the loop directly (break) without right shifts. 2) Otherwise, make right shifts at the corresponding position of the found extent, and then exit the loop (iterator=NULL). Fixes: 331573febb6a ("ext4: Add support FALLOC_FL_INSERT_RANGE for fallocate") Cc: stable@vger.kernel.org # v4.2+ Signed-off-by: Zhihao Cheng Signed-off-by: Baokun Li Reviewed-by: Jan Kara --- V1->V2: Initialize "ret" after the "again:" label to avoid return value mismatch. Refactoring reduces cycles and makes code more readable. fs/ext4/extents.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index c148bb97b527..39c9f87de0be 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -5179,6 +5179,7 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle, * and it is decreased till we reach start. */ again: + ret = 0; if (SHIFT == SHIFT_LEFT) iterator = &start; else @@ -5222,14 +5223,21 @@ ext4_ext_shift_extents(struct inode *inode, handle_t *handle, ext4_ext_get_actual_len(extent); } else { extent = EXT_FIRST_EXTENT(path[depth].p_hdr); - if (le32_to_cpu(extent->ee_block) > 0) + if (le32_to_cpu(extent->ee_block) > start) *iterator = le32_to_cpu(extent->ee_block) - 1; - else - /* Beginning is reached, end of the loop */ + else if (le32_to_cpu(extent->ee_block) == start) iterator = NULL; - /* Update path extent in case we need to stop */ - while (le32_to_cpu(extent->ee_block) < start) + else { + extent = EXT_LAST_EXTENT(path[depth].p_hdr); + while (le32_to_cpu(extent->ee_block) >= start) + extent--; + + if (extent == EXT_LAST_EXTENT(path[depth].p_hdr)) + break; + extent++; + iterator = NULL; + } path[depth].p_ext = extent; } ret = ext4_ext_shift_path_extents(path, shift, inode,