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=-9.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,T_DKIMWL_WL_HIGH,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 1DEA5C282DD for ; Thu, 23 May 2019 17:23:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E2D5320862 for ; Thu, 23 May 2019 17:23:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="UmAeUaK0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730987AbfEWRXw (ORCPT ); Thu, 23 May 2019 13:23:52 -0400 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:53026 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731038AbfEWRXw (ORCPT ); Thu, 23 May 2019 13:23:52 -0400 Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.16.0.27/8.16.0.27) with SMTP id x4NHMmGr030412 for ; Thu, 23 May 2019 10:23:51 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=QBaoodoQuJB66Q7ySr6tAw7ffBG5t1gLjZA07cX8BxM=; b=UmAeUaK0Wa6wfNKxgCpl7neEBHd8a433Mqj3r1VgRYVYUN2G3CAsorrG5upjfyGVORrf 5Z1/KLvRl8qEzplab0fhOOym425gCdqs/QbzijxXo2WcXopzhgQ+VFcMJf01IGCyjOX2 8j0ZPg+SDaubQ2Q+6FYuYnvO1LmE9omzELM= Received: from mail.thefacebook.com (mailout.thefacebook.com [199.201.64.23]) by m0001303.ppops.net with ESMTP id 2snwyh8fgb-8 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Thu, 23 May 2019 10:23:51 -0700 Received: from mx-out.facebook.com (2620:10d:c081:10::13) by mail.thefacebook.com (2620:10d:c081:35::126) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA) id 15.1.1713.5; Thu, 23 May 2019 10:23:50 -0700 Received: by devbig006.ftw2.facebook.com (Postfix, from userid 4523) id 0ADE562E1885; Thu, 23 May 2019 10:23:49 -0700 (PDT) Smtp-Origin-Hostprefix: devbig From: Song Liu Smtp-Origin-Hostname: devbig006.ftw2.facebook.com To: , CC: , "Guilherme G. Piccoli" , Song Liu Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH 1/2] block: Fix a NULL pointer dereference in generic_make_request() Date: Thu, 23 May 2019 10:23:44 -0700 Message-ID: <20190523172345.1861077-1-songliubraving@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-05-23_14:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905230117 X-FB-Internal: deliver Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: "Guilherme G. Piccoli" Commit 37f9579f4c31 ("blk-mq: Avoid that submitting a bio concurrently with device removal triggers a crash") introduced a NULL pointer dereference in generic_make_request(). The patch sets q to NULL and enter_succeeded to false; right after, there's an 'if (enter_succeeded)' which is not taken, and then the 'else' will dereference q in blk_queue_dying(q). This patch just moves the 'q = NULL' to a point in which it won't trigger the oops, although the semantics of this NULLification remains untouched. A simple test case/reproducer is as follows: a) Build kernel v5.2-rc1 with CONFIG_BLK_CGROUP=n. b) Create a raid0 md array with 2 NVMe devices as members, and mount it with an ext4 filesystem. c) Run the following oneliner (supposing the raid0 is mounted in /mnt): (dd of=/mnt/tmp if=/dev/zero bs=1M count=999 &); sleep 0.3; echo 1 > /sys/block/nvme0n1/device/device/remove (whereas nvme0n1 is the 2nd array member) This will trigger the following oops: BUG: unable to handle kernel NULL pointer dereference at 0000000000000078 PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI RIP: 0010:generic_make_request+0x32b/0x400 Call Trace: submit_bio+0x73/0x140 ext4_io_submit+0x4d/0x60 ext4_writepages+0x626/0xe90 do_writepages+0x4b/0xe0 [...] This patch has no functional changes and preserves the md/raid0 behavior when a member is removed before kernel v4.17. Cc: stable@vger.kernel.org # v4.17 Reviewed-by: Bart Van Assche Reviewed-by: Ming Lei Reviewed-by: Christoph Hellwig Tested-by: Eric Ren Fixes: 37f9579f4c31 ("blk-mq: Avoid that submitting a bio concurrently with device removal triggers a crash") Signed-off-by: Guilherme G. Piccoli Signed-off-by: Song Liu --- block/blk-core.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index a55389ba8779..d24a29244cb8 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -1074,10 +1074,8 @@ blk_qc_t generic_make_request(struct bio *bio) flags = 0; if (bio->bi_opf & REQ_NOWAIT) flags = BLK_MQ_REQ_NOWAIT; - if (blk_queue_enter(q, flags) < 0) { + if (blk_queue_enter(q, flags) < 0) enter_succeeded = false; - q = NULL; - } } if (enter_succeeded) { @@ -1108,6 +1106,7 @@ blk_qc_t generic_make_request(struct bio *bio) bio_wouldblock_error(bio); else bio_io_error(bio); + q = NULL; } bio = bio_list_pop(&bio_list_on_stack[0]); } while (bio); -- 2.17.1