Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934123AbbGHLx7 (ORCPT ); Wed, 8 Jul 2015 07:53:59 -0400 Received: from mail-ig0-f176.google.com ([209.85.213.176]:38753 "EHLO mail-ig0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932745AbbGHLx6 (ORCPT ); Wed, 8 Jul 2015 07:53:58 -0400 MIME-Version: 1.0 In-Reply-To: <1435847397-724-3-git-send-email-akinobu.mita@gmail.com> References: <1435847397-724-1-git-send-email-akinobu.mita@gmail.com> <1435847397-724-3-git-send-email-akinobu.mita@gmail.com> Date: Wed, 8 Jul 2015 19:53:57 +0800 Message-ID: Subject: Re: [PATCH v2 2/6] blk-mq: Fix use after of free q->mq_map From: Ming Lei To: Akinobu Mita Cc: Linux Kernel Mailing List , Jens Axboe Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1825 Lines: 60 On Thu, Jul 2, 2015 at 10:29 PM, Akinobu Mita wrote: > CPU hotplug handling for blk-mq (blk_mq_queue_reinit) updates > q->mq_map by blk_mq_update_queue_map() for all request queues in > all_q_list. On the other hand, q->mq_map is released before deleting > the queue from all_q_list. > > So if CPU hotplug event occurs in the window, invalid memory access > can happen. Fix it by releasing q->mq_map in blk_mq_release() to make > it happen latter than removal from all_q_list. > > Signed-off-by: Akinobu Mita > Suggested-by: Ming Lei > Cc: Jens Axboe > Cc: Ming Lei Reviewed-by: Ming Lei > --- > block/blk-mq.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index f537796..c5da908 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1928,6 +1928,9 @@ void blk_mq_release(struct request_queue *q) > kfree(hctx); > } > > + kfree(q->mq_map); > + q->mq_map = NULL; > + > kfree(q->queue_hw_ctx); > > /* ctx kobj stays in queue_ctx */ > @@ -2073,11 +2076,6 @@ void blk_mq_free_queue(struct request_queue *q) > blk_mq_free_hw_queues(q, set); > > percpu_ref_exit(&q->mq_usage_counter); > - > - kfree(q->mq_map); > - > - q->mq_map = NULL; > - > mutex_lock(&all_q_mutex); > list_del_init(&q->all_q_node); > mutex_unlock(&all_q_mutex); > -- > 1.9.1 > -- Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/