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Sat, 29 Aug 2026 00:31:29 +0000 Date: Fri, 28 Aug 2026 17:31:26 -0700 From: Alison Schofield To: Guixin Liu CC: Davidlohr Bueso , Jonathan Cameron , Dave Jiang , Vishal Verma , Dan Williams , Ira Weiny , Li Ming , Subject: Re: [PATCH v3] cxl/core: Fix dport use-after-free via the einj_inject debugfs file Message-ID: References: <20260828074752.3336779-1-kanie@linux.alibaba.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260828074752.3336779-1-kanie@linux.alibaba.com> X-ClientProxiedBy: BY1P220CA0014.NAMP220.PROD.OUTLOOK.COM (2603:10b6:a03:59d::9) To DS4PPF0BAC23327.namprd11.prod.outlook.com (2603:10b6:f:fc02::9) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS4PPF0BAC23327:EE_|IA1PR11MB7755:EE_ X-MS-Office365-Filtering-Correlation-Id: a24b35b8-8d31-4cf5-abd2-08df0564de61 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|23010399003|1800799024|10067099003|6133799003|18002099003|22082099003|56012099006|11063799006; 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Unbinding > the dport host frees the dport and leaves einj_inject behind, so writing > the file dereferences freed memory: > > BUG: KASAN: slab-use-after-free in cxl_einj_inject+0xa1/0xf0 [cxl_core] > Read of size 1 at addr ffff88810880ac90 by task bash/1690 > cxl_einj_inject+0xa1/0xf0 [cxl_core] > debugfs_attr_write+0x61/0xb0 > full_proxy_write+0xfc/0x1c0 > vfs_write+0x1d4/0xe60 > Allocated by task 213: > __devm_cxl_add_dport+0x1e1/0x14d0 [cxl_core] > cxl_port_add_dport+0xd6/0x200 [cxl_port] > Freed by task 1622: > release_nodes+0xfa/0x2c0 > devres_release_all+0x113/0x1a0 > device_unbind_cleanup+0x76/0x260 > unbind_store+0xde/0x100 > > The stale directory also prevents recreation on rebind. > > Remove the per-dport debugfs directory when the dport host is released. > > Found by code inspection, then reproduced on a QEMU CXL topology with > KASAN (the einj_cxl_is_initialized() guard had to be forced open, as > QEMU emits no EINJ table). Unpatched, writing the leftover file after > unbind gives the splat above, and rebind hits "already exists in > 'cxl'". Patched, the directory goes away with the dport and rebind > recreates a working einj_inject. > > Fixes: 8039804cfa73 ("cxl/core: Add CXL EINJ debugfs files") > Signed-off-by: Guixin Liu > Reviewed-by: Richard Cheng > Reviewed-by: Li Ming Thanks for the changelog updatges Guixin. DaveJ - KASAN trace could be left out upon applying. Reviewed-by: Alison Schofield