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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 C7D02C433EF for ; Sun, 19 Sep 2021 14:44:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B07F361242 for ; Sun, 19 Sep 2021 14:44:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233270AbhISOqP (ORCPT ); Sun, 19 Sep 2021 10:46:15 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:64487 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233184AbhISOqH (ORCPT ); Sun, 19 Sep 2021 10:46:07 -0400 Received: from fsav117.sakura.ne.jp (fsav117.sakura.ne.jp [27.133.134.244]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 18JEiXaH043914; Sun, 19 Sep 2021 23:44:33 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav117.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav117.sakura.ne.jp); Sun, 19 Sep 2021 23:44:33 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav117.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 18JEiTKq043904 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 19 Sep 2021 23:44:33 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: [PATCH] block: genhd: fix double kfree() in __alloc_disk_node() From: Tetsuo Handa To: axboe@kernel.dk, Christoph Hellwig References: <0000000000004a5adf05cc593ca9@google.com> <41766564-08cb-e7f2-4cb2-9ad102f21324@I-love.SAKURA.ne.jp> Cc: linux-block@vger.kernel.org Message-ID: <3999c511-cd27-1554-d3a6-4288c3eca298@i-love.sakura.ne.jp> Date: Sun, 19 Sep 2021 23:44:29 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <41766564-08cb-e7f2-4cb2-9ad102f21324@I-love.SAKURA.ne.jp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org syzbot is reporting use-after-free read at bdev_free_inode() [1], for kfree() from __alloc_disk_node() is called before bdev_free_inode() (which is called after RCU grace period) reads bdev->bd_disk and calls kfree(bdev->bd_disk). Fix use-after-free read followed by double kfree() problem by explicitly resetting bdev->bd_disk to NULL before calling iput(). Link: https://syzkaller.appspot.com/bug?extid=8281086e8a6fbfbd952a [1] Reported-by: syzbot Signed-off-by: Tetsuo Handa --- This patch is not tested due to lack of reproducer. Is this fix correct? block/bdev.c | 1 + block/genhd.c | 1 + 2 files changed, 2 insertions(+) diff --git a/block/bdev.c b/block/bdev.c index cf2780cb44a7..f6b8bac83bd8 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -495,6 +495,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno) bdev->bd_inode = inode; bdev->bd_stats = alloc_percpu(struct disk_stats); if (!bdev->bd_stats) { + bdev->bd_disk = NULL; iput(inode); return NULL; } diff --git a/block/genhd.c b/block/genhd.c index 7b6e5e1cf956..496e8458c357 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -1268,6 +1268,7 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id, out_destroy_part_tbl: xa_destroy(&disk->part_tbl); + disk->part0->bd_disk = NULL; iput(disk->part0->bd_inode); out_free_bdi: bdi_put(disk->bdi); -- 2.18.4