Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93617C433F5 for ; Fri, 17 Dec 2021 15:31:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238654AbhLQPbx (ORCPT ); Fri, 17 Dec 2021 10:31:53 -0500 Received: from foss.arm.com ([217.140.110.172]:58910 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238782AbhLQPbO (ORCPT ); Fri, 17 Dec 2021 10:31:14 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D6C631476; Fri, 17 Dec 2021 07:31:13 -0800 (PST) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 6D49D3F774; Fri, 17 Dec 2021 07:31:12 -0800 (PST) From: Robin Murphy To: joro@8bytes.org, will@kernel.org Cc: iommu@lists.linux-foundation.org, suravee.suthikulpanit@amd.com, baolu.lu@linux.intel.com, willy@infradead.org, linux-kernel@vger.kernel.org, john.garry@huawei.com, linux-mm@kvack.org, hch@lst.de, Xiongfeng Wang Subject: [PATCH v3 1/9] iommu/iova: Fix race between FQ timeout and teardown Date: Fri, 17 Dec 2021 15:30:55 +0000 Message-Id: <0a365e5b07f14b7344677ad6a9a734966a8422ce.1639753638.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.28.0.dirty In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Xiongfeng Wang It turns out to be possible for hotplugging out a device to reach the stage of tearing down the device's group and default domain before the domain's flush queue has drained naturally. At this point, it is then possible for the timeout to expire just before the del_timer() call in free_iova_flush_queue(), such that we then proceed to free the FQ resources while fq_flush_timeout() is still accessing them on another CPU. Crashes due to this have been observed in the wild while removing NVMe devices. Close the race window by using del_timer_sync() to safely wait for any active timeout handler to finish before we start to free things. We already avoid any locking in free_iova_flush_queue() since the FQ is supposed to be inactive anyway, so the potential deadlock scenario does not apply. Fixes: 9a005a800ae8 ("iommu/iova: Add flush timer") Reviewed-by: John Garry Signed-off-by: Xiongfeng Wang [ rm: rewrite commit message ] Signed-off-by: Robin Murphy --- drivers/iommu/iova.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 9e8bc802ac05..920fcc27c9a1 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -83,8 +83,7 @@ static void free_iova_flush_queue(struct iova_domain *iovad) if (!has_iova_flush_queue(iovad)) return; - if (timer_pending(&iovad->fq_timer)) - del_timer(&iovad->fq_timer); + del_timer_sync(&iovad->fq_timer); fq_destroy_all_entries(iovad); -- 2.28.0.dirty