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=ham 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 17450C433C1 for ; Sun, 28 Mar 2021 19:12:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DE2D56197E for ; Sun, 28 Mar 2021 19:12:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231604AbhC1TMP (ORCPT ); Sun, 28 Mar 2021 15:12:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:50228 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231586AbhC1TLp (ORCPT ); Sun, 28 Mar 2021 15:11:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6E22361958; Sun, 28 Mar 2021 19:11:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1616958704; bh=vBn3GFWUPM1yvyEZqog89jRYUymz8qXwY6TDU2GPZfE=; h=Date:From:To:Subject:From; b=iqCyVQFRWrMXbzZN6omPsMn5npElg+L65jOJveRInPihmpB70J8UiIar0mM7i8mmf 1I5UTvXzHxc96u9HyNDCAp7UTI8LM0saKlhFTZ/Yrdb+l9/hwW+/1eP3dZUSboLp1H uc2FqmnrY2R5QtL3Hv7zp95TigMMRJjUuIxe0/WI= Date: Sun, 28 Mar 2021 12:11:44 -0700 From: akpm@linux-foundation.org To: apopple@nvidia.com, dan.j.williams@intel.com, daniel.vetter@ffwll.ch, david@redhat.com, gregkh@linuxfoundation.org, jbarnes@virtuousgeek.org, jglisse@redhat.com, jhubbard@nvidia.com, mm-commits@vger.kernel.org Subject: + kernel-resource-fix-locking-in-request_free_mem_region.patch added to -mm tree Message-ID: <20210328191144.okUhn91YM%akpm@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 The patch titled Subject: kernel/resource: Fix locking in request_free_mem_region has been added to the -mm tree. Its filename is kernel-resource-fix-locking-in-request_free_mem_region.patch This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/kernel-resource-fix-locking-in-request_free_mem_region.patch and later at https://ozlabs.org/~akpm/mmotm/broken-out/kernel-resource-fix-locking-in-request_free_mem_region.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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. region_intersects() obtains a read lock before walking the resource tree to protect against concurrent changes. However it drops the lock prior to returning. This means by the time request_mem_region() is called in request_free_mem_region() another thread may have already reserved the requested region resulting 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); To fix this create versions of region_intersects() and request_mem_region() that allow the caller to take the appropriate lock such that it may be held over the required calls. Instead of creating another version of devm_request_mem_region() that doesn't take the lock open-code it to allow the caller to pre-allocate the required memory prior to taking the lock. Link: https://lkml.kernel.org/r/20210326012035.3853-1-apopple@nvidia.com Fixes: 0c385190392d8 ("resource: add a not device managed request_free_mem_region variant") Fixes: 0092908d16c60 ("mm: factor out a devm_request_free_mem_region helper") Fixes: 4ef589dc9b10c ("mm/hmm/devmem: device memory hotplug using ZONE_DEVICE") Signed-off-by: Alistair Popple Cc: David Hildenbrand Cc: Daniel Vetter Cc: Dan Williams Cc: Greg Kroah-Hartman Cc: John Hubbard Cc: Jerome Glisse Cc: Jesse Barnes Signed-off-by: Andrew Morton --- kernel/resource.c | 146 ++++++++++++++++++++++++++++---------------- 1 file changed, 94 insertions(+), 52 deletions(-) --- a/kernel/resource.c~kernel-resource-fix-locking-in-request_free_mem_region +++ a/kernel/resource.c @@ -523,6 +523,34 @@ int __weak page_is_ram(unsigned long pfn } EXPORT_SYMBOL_GPL(page_is_ram); +static int __region_intersects(resource_size_t start, size_t size, + unsigned long flags, unsigned long desc) +{ + struct resource res; + int type = 0; int other = 0; + struct resource *p; + + res.start = start; + res.end = start + size - 1; + + for (p = iomem_resource.child; p ; p = p->sibling) { + bool is_type = (((p->flags & flags) == flags) && + ((desc == IORES_DESC_NONE) || + (desc == p->desc))); + + if (resource_overlaps(p, &res)) + is_type ? type++ : other++; + } + + if (type == 0) + return REGION_DISJOINT; + + if (other == 0) + return REGION_INTERSECTS; + + return REGION_MIXED; +} + /** * region_intersects() - determine intersection of region with known resources * @start: region start address @@ -546,31 +574,12 @@ EXPORT_SYMBOL_GPL(page_is_ram); int region_intersects(resource_size_t start, size_t size, unsigned long flags, unsigned long desc) { - struct resource res; - int type = 0; int other = 0; - struct resource *p; - - res.start = start; - res.end = start + size - 1; + int rc; read_lock(&resource_lock); - for (p = iomem_resource.child; p ; p = p->sibling) { - bool is_type = (((p->flags & flags) == flags) && - ((desc == IORES_DESC_NONE) || - (desc == p->desc))); - - if (resource_overlaps(p, &res)) - is_type ? type++ : other++; - } + rc = __region_intersects(start, size, flags, desc); read_unlock(&resource_lock); - - if (type == 0) - return REGION_DISJOINT; - - if (other == 0) - return REGION_INTERSECTS; - - return REGION_MIXED; + return rc; } EXPORT_SYMBOL_GPL(region_intersects); @@ -1171,31 +1180,17 @@ struct address_space *iomem_get_mapping( return smp_load_acquire(&iomem_inode)->i_mapping; } -/** - * __request_region - create a new busy resource region - * @parent: parent resource descriptor - * @start: resource start address - * @n: resource region size - * @name: reserving caller's ID string - * @flags: IO resource flags - */ -struct resource * __request_region(struct resource *parent, - resource_size_t start, resource_size_t n, - const char *name, int flags) +static bool request_region_locked(struct resource *parent, + struct resource *res, resource_size_t start, + resource_size_t n, const char *name, int flags) { - DECLARE_WAITQUEUE(wait, current); - struct resource *res = alloc_resource(GFP_KERNEL); struct resource *orig_parent = parent; - - if (!res) - return NULL; + DECLARE_WAITQUEUE(wait, current); res->name = name; res->start = start; res->end = start + n - 1; - write_lock(&resource_lock); - for (;;) { struct resource *conflict; @@ -1230,16 +1225,39 @@ struct resource * __request_region(struc write_lock(&resource_lock); continue; } - /* Uhhuh, that didn't work out.. */ - free_resource(res); - res = NULL; - break; + return false; } - write_unlock(&resource_lock); if (res && orig_parent == &iomem_resource) revoke_iomem(res); + return true; +} + +/** + * __request_region - create a new busy resource region + * @parent: parent resource descriptor + * @start: resource start address + * @n: resource region size + * @name: reserving caller's ID string + * @flags: IO resource flags + */ +struct resource *__request_region(struct resource *parent, + resource_size_t start, resource_size_t n, + const char *name, int flags) +{ + struct resource *res = alloc_resource(GFP_KERNEL); + + if (!res) + return NULL; + + write_lock(&resource_lock); + if (!request_region_locked(parent, res, start, n, name, flags)) { + /* Uhhuh, that didn't work out.. */ + free_resource(res); + res = NULL; + } + write_unlock(&resource_lock); return res; } EXPORT_SYMBOL(__request_region); @@ -1779,26 +1797,50 @@ static struct resource *__request_free_m { resource_size_t end, addr; struct resource *res; + struct region_devres *dr = NULL; + + 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); + } + } size = ALIGN(size, 1UL << PA_SECTION_SHIFT); end = min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1); addr = end - size + 1UL; + 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(&iomem_resource, res, addr, + size, name, 0)) + break; + res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY; + if (dev) { + dr->parent = &iomem_resource; + dr->start = addr; + dr->n = size; + devres_add(dev, dr); + } + + write_unlock(&resource_lock); return res; } + write_unlock(&resource_lock); + free_resource(res); + return ERR_PTR(-ERANGE); } _ Patches currently in -mm which might be from apopple@nvidia.com are kernel-resource-fix-locking-in-request_free_mem_region.patch