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Fri, 26 Mar 2021 00:27:09 +0000 From: Alistair Popple To: CC: , , , , , Alistair Popple Subject: [PATCH] kernel/resource: Fix locking in request_free_mem_region Date: Fri, 26 Mar 2021 11:26:27 +1100 Message-ID: <20210326002627.2940-1-apopple@nvidia.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 9a389eab-8f5e-4f33-d4ae-08d8efede56e X-MS-TrafficTypeDiagnostic: MN2PR12MB3053: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6790; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid03.nvidia.com;CAT:NONE;SFS:(4636009)(376002)(346002)(39860400002)(136003)(396003)(36840700001)(46966006)(82740400003)(8676002)(8936002)(1076003)(7636003)(6666004)(36756003)(336012)(6916009)(36860700001)(86362001)(82310400003)(47076005)(478600001)(426003)(316002)(36906005)(107886003)(2906002)(54906003)(70206006)(83380400001)(70586007)(5660300002)(26005)(186003)(356005)(16526019)(2616005)(4326008);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Mar 2021 00:27:10.7359 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 9a389eab-8f5e-4f33-d4ae-08d8efede56e X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT037.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB3053 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Alistair Popple --- kernel/resource.c | 146 +++++++++++++++++++++++++++++----------------- 1 file changed, 94 insertions(+), 52 deletions(-) diff --git a/kernel/resource.c b/kernel/resource.c index 627e61b0c124..2d4652383dd2 100644 --- a/kernel/resource.c +++ b/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(void) 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(struct resource *parent, 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_mem_region(struct device *dev, { 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); } -- 2.20.1