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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 D7BBDC433ED for ; Fri, 7 May 2021 01:05:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BE3C0613D8 for ; Fri, 7 May 2021 01:05:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234132AbhEGBGc (ORCPT ); Thu, 6 May 2021 21:06:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:47600 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231297AbhEGBGb (ORCPT ); Thu, 6 May 2021 21:06:31 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id E0FD861289; Fri, 7 May 2021 01:05:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620349531; bh=brZ9xkB7+GP4q07L2w+/BS9CwlZgMzL0lrghYvb3+EE=; h=Date:From:To:Subject:In-Reply-To:From; b=R29qoHsymC7UDq7FQdoPtSuHs+ha+cq6JPXbFs8JN7ZUUdJ4mPKOlWo2HCXZYrct7 elzRdoZUCRoFqjV03TCdfxIa3ACWA2qnsxI2D3kO3nXLZZddSGBXGmCNmaDna33QB2 PlvMJKRLkA5d8Q7FZT29ClITVhuVrG8AdzBUbtok= Date: Thu, 06 May 2021 18:05:30 -0700 From: Andrew Morton To: akpm@linux-foundation.org, apopple@nvidia.com, bsingharora@gmail.com, dan.j.williams@intel.com, daniel.vetter@ffwll.ch, david@redhat.com, gregkh@linuxfoundation.org, jglisse@redhat.com, jhubbard@nvidia.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, smuchun@gmail.com, torvalds@linux-foundation.org Subject: [patch 66/91] kernel/resource: fix locking in request_free_mem_region Message-ID: <20210507010530.uEl5utzt5%akpm@linux-foundation.org> In-Reply-To: <20210506180126.03e1baee7ca52bedb6cc6003@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Alistair Popple Subject: kernel/resource: fix locking in request_free_mem_region request_free_mem_region() is used to find an empty range of physical addresses for hotplugging ZONE_DEVICE memory. It does this by iterating over the range of possible addresses using region_intersects() to see if the range is free before calling request_mem_region() to allocate the region. However the resource_lock is dropped between these two calls meaning by the time request_mem_region() is called in request_free_mem_region() another thread may have already reserved the requested region. This results in unexpected failures and a message in the kernel log from hitting this condition: /* * mm/hmm.c reserves physical addresses which then * become unavailable to other users. Conflicts are * not expected. Warn to aid debugging if encountered. */ if (conflict->desc == IORES_DESC_DEVICE_PRIVATE_MEMORY) { pr_warn("Unaddressable device %s %pR conflicts with %pR", conflict->name, conflict, res); These unexpected failures can be corrected by holding resource_lock across the two calls. This also requires memory allocation to be performed prior to taking the lock. Link: https://lkml.kernel.org/r/20210419070109.4780-3-apopple@nvidia.com Signed-off-by: Alistair Popple Reviewed-by: David Hildenbrand Cc: Balbir Singh Cc: Daniel Vetter Cc: Dan Williams Cc: Greg Kroah-Hartman Cc: Jerome Glisse Cc: John Hubbard Cc: Muchun Song Signed-off-by: Andrew Morton --- kernel/resource.c | 45 +++++++++++++++++++++++++++++++++++++------- 1 file changed, 38 insertions(+), 7 deletions(-) --- a/kernel/resource.c~kernel-resource-fix-locking-in-request_free_mem_region +++ a/kernel/resource.c @@ -1780,25 +1780,56 @@ static struct resource *__request_free_m { resource_size_t end, addr; struct resource *res; + struct region_devres *dr = NULL; size = ALIGN(size, 1UL << PA_SECTION_SHIFT); end = min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1); addr = end - size + 1UL; + res = alloc_resource(GFP_KERNEL); + if (!res) + return ERR_PTR(-ENOMEM); + + if (dev) { + dr = devres_alloc(devm_region_release, + sizeof(struct region_devres), GFP_KERNEL); + if (!dr) { + free_resource(res); + return ERR_PTR(-ENOMEM); + } + } + + write_lock(&resource_lock); for (; addr > size && addr >= base->start; addr -= size) { - if (region_intersects(addr, size, 0, IORES_DESC_NONE) != + if (__region_intersects(addr, size, 0, IORES_DESC_NONE) != REGION_DISJOINT) continue; - if (dev) - res = devm_request_mem_region(dev, addr, size, name); - else - res = request_mem_region(addr, size, name); - if (!res) - return ERR_PTR(-ENOMEM); + if (!__request_region_locked(res, &iomem_resource, addr, size, + name, 0)) + break; + + if (dev) { + dr->parent = &iomem_resource; + dr->start = addr; + dr->n = size; + devres_add(dev, dr); + } + res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY; + write_unlock(&resource_lock); + + /* + * A driver is claiming this region so revoke any mappings. + */ + revoke_iomem(res); return res; } + write_unlock(&resource_lock); + + free_resource(res); + if (dr) + devres_free(dr); return ERR_PTR(-ERANGE); } _