From patchwork Sun Oct 1 16:25:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Benjamin Block X-Patchwork-Id: 9979775 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7666C60365 for ; Sun, 1 Oct 2017 16:25:44 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 590DF28956 for ; Sun, 1 Oct 2017 16:25:44 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4DDD428968; Sun, 1 Oct 2017 16:25:44 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4CD6B28966 for ; Sun, 1 Oct 2017 16:25:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751153AbdJAQZl (ORCPT ); Sun, 1 Oct 2017 12:25:41 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:33546 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751118AbdJAQZj (ORCPT ); Sun, 1 Oct 2017 12:25:39 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v91GJZYv054894 for ; Sun, 1 Oct 2017 12:25:39 -0400 Received: from e06smtp11.uk.ibm.com (e06smtp11.uk.ibm.com [195.75.94.107]) by mx0a-001b2d01.pphosted.com with ESMTP id 2daehdk9gv-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 01 Oct 2017 12:25:39 -0400 Received: from localhost by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Sun, 1 Oct 2017 17:25:35 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v91GPYIe7602244 for ; Sun, 1 Oct 2017 16:25:34 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7D93CAE04D for ; Sun, 1 Oct 2017 17:20:09 +0100 (BST) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 55521AE045 for ; Sun, 1 Oct 2017 17:20:09 +0100 (BST) Received: from bblock-ThinkPad-W530 (unknown [9.145.52.73]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP for ; Sun, 1 Oct 2017 17:20:09 +0100 (BST) Received: from bblock (uid 1000) (envelope-from bblock@linux.vnet.ibm.com) id 30028d1e by bblock-ThinkPad-W530 (DragonFly Mail Agent v0.9); Sun, 01 Oct 2017 18:25:34 +0200 From: Benjamin Block To: Jens Axboe Cc: Benjamin Block , linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, Christoph Hellwig , Steffen Maier , stable@vger.kernel.org Subject: [PATCH v2 1/1] bsg-lib: fix use-after-free under memory-pressure Date: Sun, 1 Oct 2017 18:25:23 +0200 X-Mailer: git-send-email 2.14.2 MIME-Version: 1.0 X-TM-AS-GCONF: 00 x-cbid: 17100116-0040-0000-0000-000003FE90BE X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17100116-0041-0000-0000-0000209FF080 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-10-01_07:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=2 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1707230000 definitions=main-1710010243 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When under memory-pressure it is possible that the mempool which backs the 'struct request_queue' will make use of up to BLKDEV_MIN_RQ count emergency buffers - in case it can't get a regular allocation. These buffers are preallocated and once they are also used, they are re-supplied with old finished requests from the same request_queue (see mempool_free()). The bug is, when re-supplying the emergency pool, the old requests are not again ran through the callback mempool_t->alloc(), and thus also not through the callback bsg_init_rq(). Thus we skip initialization, and while the sense-buffer still should be good, scsi_request->cmd might have become to be an invalid pointer in the meantime. When the request is initialized in bsg.c, and the user's CDB is larger than BLK_MAX_CDB, bsg will replace it with a custom allocated buffer, which is freed when the user's command is finished, thus it dangles afterwards. When next a command is sent by the user that has a smaller/similar CDB as BLK_MAX_CDB, bsg will assume that scsi_request->cmd is backed by scsi_request->__cmd, will not make a custom allocation, and write into undefined memory. Fix this by splitting bsg_init_rq() into two functions: - bsg_init_rq() is changed to only do the allocation of the sense-buffer, which is used to back the bsg job's reply buffer. This pointer should never change during the lifetime of a scsi_request, so it doesn't need re-initialization. - bsg_initialize_rq() is a new function that makes use of 'struct request_queue's initialize_rq_fn callback (which was introduced in v4.12). This is always called before the request is given out via blk_get_request(). This function does the remaining initialization that was previously done in bsg_init_rq(), and will also do it when the request is taken from the emergency-pool of the backing mempool. Fixes: 50b4d485528d ("bsg-lib: fix kernel panic resulting from missing allocation of reply-buffer") Cc: # 4.11+ Reviewed-by: Christoph Hellwig Signed-off-by: Benjamin Block Reviewed-by: Christoph Hellwig --- Notes: I did test this on zFCP with FC CT commands send via the ioctl() and write() system-call. That did work fine. But I would very much appreciate if anyone could run this against an other HBA or even an other implementer of bsg-lib, such as now SAS, because I have no access to such hardware here. This should make no difference to the normal cases - where each request is allocated via slab - with- or without this patch; if I didn't miss anything. Only the order is a bit mixed up - the memset is done after the sense-allocation, so I have to buffer the sense-pointer for that. But otherwise there is no difference I am aware of, so it should behave the same (does for me). I could not reproduce the memory-pressure case here in the lab.. I don't see any reason why it should work now, but I am open to suggestions :) Beste Grüße / Best regards, - Benjamin Block Changes in v2: - Renamed function names to reflect the function-pointer names in request_queue block/bsg-lib.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/block/bsg-lib.c b/block/bsg-lib.c index c82408c7cc3c..ff5a158b22fa 100644 --- a/block/bsg-lib.c +++ b/block/bsg-lib.c @@ -208,20 +208,34 @@ static int bsg_init_rq(struct request_queue *q, struct request *req, gfp_t gfp) struct bsg_job *job = blk_mq_rq_to_pdu(req); struct scsi_request *sreq = &job->sreq; - memset(job, 0, sizeof(*job)); + /* called right after the request is allocated for the request_queue */ - scsi_req_init(sreq); - sreq->sense_len = SCSI_SENSE_BUFFERSIZE; - sreq->sense = kzalloc(sreq->sense_len, gfp); + sreq->sense = kzalloc(SCSI_SENSE_BUFFERSIZE, gfp); if (!sreq->sense) return -ENOMEM; + return 0; +} + +static void bsg_initialize_rq(struct request *req) +{ + struct bsg_job *job = blk_mq_rq_to_pdu(req); + struct scsi_request *sreq = &job->sreq; + void *sense = sreq->sense; + + /* called right before the request is given to the request_queue user */ + + memset(job, 0, sizeof(*job)); + + scsi_req_init(sreq); + + sreq->sense = sense; + sreq->sense_len = SCSI_SENSE_BUFFERSIZE; + job->req = req; - job->reply = sreq->sense; + job->reply = sense; job->reply_len = sreq->sense_len; job->dd_data = job + 1; - - return 0; } static void bsg_exit_rq(struct request_queue *q, struct request *req) @@ -252,6 +266,7 @@ struct request_queue *bsg_setup_queue(struct device *dev, const char *name, q->cmd_size = sizeof(struct bsg_job) + dd_job_size; q->init_rq_fn = bsg_init_rq; q->exit_rq_fn = bsg_exit_rq; + q->initialize_rq_fn = bsg_initialize_rq; q->request_fn = bsg_request_fn; ret = blk_init_allocated_queue(q);