From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753336AbbG2OWz (ORCPT ); Wed, 29 Jul 2015 10:22:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43686 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753098AbbG2OWw (ORCPT ); Wed, 29 Jul 2015 10:22:52 -0400 From: Jeff Moyer To: Ming Lei , Sam Bradshaw , Asai Thambi SP Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, dmilburn@redhat.com Subject: [patch|rfc] mtip32x: fix regression introduced by blk-mq per-hctx flush X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 29 Jul 2015 10:22:50 -0400 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, After commit f70ced091707 (blk-mq: support per-distpatch_queue flush machinery), the mtip32xx driver may oops upon module load due to walking off the end of an array in mtip_init_cmd. On initialization of the flush_rq, init_request is called with request_index >= the maximum queue depth the driver supports. For mtip32xx, this value is used to index into an array. What this means is that the driver will walk off the end of the array, and either oops or cause random memory corruption. The problem is easily reproduced by doing modprobe/rmmod of the mtip32xx driver in a loop. I can typically reproduce the problem in about 30 seconds. Now, in the case of mtip32xx, it actually doesn't support flush/fua, so I think we can simply return without doing anything. In addition, no other mq-enabled driver does anything with the request_index passed into init_request(), so no other driver is affected. However, I'm not really sure what is expected of drivers. Ming, what did you envision drivers would do when initializing the flush requests? Signed-off-by: Jeff Moyer diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c index 4a2ef09..f504232 100644 --- a/drivers/block/mtip32xx/mtip32xx.c +++ b/drivers/block/mtip32xx/mtip32xx.c @@ -3756,6 +3756,14 @@ static int mtip_init_cmd(void *data, struct request *rq, unsigned int hctx_idx, struct mtip_cmd *cmd = blk_mq_rq_to_pdu(rq); u32 host_cap_64 = readl(dd->mmio + HOST_CAP) & HOST_CAP_64; + /* + * For flush requests, request_idx starts at the end of the + * tag space. Since we don't support FLUSH/FUA, simply return + * 0 as there's nothing to be done. + */ + if (request_idx >= MTIP_MAX_COMMAND_SLOTS) + return 0; + cmd->command = dmam_alloc_coherent(&dd->pdev->dev, CMD_DMA_ALLOC_SZ, &cmd->command_dma, GFP_KERNEL); if (!cmd->command)