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Wysocki" CC: Len Brown , Tony Luck , "Punit Agrawal" , , Subject: [PATCH] ACPI: sysfs: Map only the requested range in acpi_data_show() Date: Tue, 13 Oct 2026 11:07:28 -0700 Message-ID: <20261013180728.957618-1-jamien@nvidia.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CY8PEPF00000053:EE_|LV8PR12MB9642:EE_ X-MS-Office365-Filtering-Correlation-Id: b7341465-f674-4ab1-a39b-08df2954e698 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700016|23010399003|376014|1800799024|82310400026|56012099006|11063799006|261009223027099003|10067099003|18002099003|4133799003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.118.233;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge2.nvidia.com;CAT:NONE;SFS:(13230040)(36860700016)(23010399003)(376014)(1800799024)(82310400026)(56012099006)(11063799006)(261009223027099003)(10067099003)(18002099003)(4133799003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: TufFLlwmhaycK83VpEA+iix6Qy9Zzxli78Z3dhaXLCk43g2Qab7N9q+vqP/KWSXLOmTEuCy0Krf53Td8XxzNQ9aohTS6raLBkR0Xmar26yzPvSsDhrZAwZgqAPG2gWoQ+ylLCsXDXKB+JxfKqUGyNaUeowf0h9gmjJ9Ea0YBPtufHNIi1xiPFpM9ScIeFlWF0lN4NuEhYzOywCwG/pAJosFHl9KFavuUxuwhLZq3f83SxKXE3/78dlBsXUTTTgFsBF7rTPHNPBFbDXwul9Zrug4kPFLXaaH6n21njRGzasZ4XvV9LGO8FNFusVWPnJ3/iuWicRpajQ2b16D+GGgrYClgFOh7xAK9JiHQ+dApBEEvGj1mFGgeZmONEoPBXbuupGE+l6h5QI5txADyJf492ZeUgXO5izrCZ1q8RRhiNB4L8NL7Ye1p9ND5+pUWuijY X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2026 18:07:53.0810 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b7341465-f674-4ab1-a39b-08df2954e698 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CY8PEPF00000053.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9642 acpi_data_show() maps the whole data region on every read(), although it copies at most count bytes and sysfs passes at most PAGE_SIZE bytes per call. acpi_os_unmap_iomem() defers the iounmap until after an RCU grace period, so a process reading one of these files in a loop keeps many full-size mappings in flight. Map only the range being read. acpi_os_map_iomem() rounds the mapping to page boundaries, so each mapping is now at most two pages, whatever the size of the region. A malformed table can describe a region that wraps around the end of the physical address space. acpi_os_map_iomem() doesn't check for that, and its lookup of existing mappings then matches an unrelated mapping, with or without this change. Fail reads of such a region before mapping anything. Assisted-by: LLM Signed-off-by: Jamie Nguyen --- As discussed on the BDAT v2 thread: https://lore.kernel.org/r/CAJZ5v0ixQ_5jmrfm4mz50tZtCEq6nJt1b2eMoBdhr0f3AY+k7w@mail.gmail.com This doesn't depend on that series and applies on its own. Tested on an arm64 server with 4K and 64K pages, with the BDAT v2 series applied: - The BERT and BDAT data files match /dev/mem when read whole, byte by byte, page by page, and across page boundaries. - Each read maps at most two pages. With 4K pages, looping full reads of the 90754-byte BDAT file kept at most 167 MiB of vmalloc space mapped (1740 MiB before), and looping 1-byte reads at most 355 MiB (3090 MiB before). - Malformed BERT tables loaded via initrd table upgrade, with regions that wrap around the end of the physical address space, fail every read with -EINVAL. drivers/acpi/sysfs.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c index dd4a99f09efea65..138009659a7b55f 100644 --- a/drivers/acpi/sysfs.c +++ b/drivers/acpi/sysfs.c @@ -419,6 +419,7 @@ static ssize_t acpi_data_show(struct file *filp, struct kobject *kobj, struct acpi_data_attr *data_attr; void __iomem *base; ssize_t size; + u64 end; data_attr = container_of(bin_attr, struct acpi_data_attr, attr); size = data_attr->attr.size; @@ -432,13 +433,17 @@ static ssize_t acpi_data_show(struct file *filp, struct kobject *kobj, if (count > size - offset) count = size - offset; - base = acpi_os_map_iomem(data_attr->addr, size); + /* acpi_os_map_iomem() can't handle a range that wraps around */ + if (check_add_overflow(data_attr->addr, size, &end)) + return -EINVAL; + + base = acpi_os_map_iomem(data_attr->addr + offset, count); if (!base) return -ENOMEM; - memcpy_fromio(buf, base + offset, count); + memcpy_fromio(buf, base, count); - acpi_os_unmap_iomem(base, size); + acpi_os_unmap_iomem(base, count); return count; } -- 2.43.0