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Thu, 6 Aug 2026 16:47:03 +0000 Message-ID: Date: Thu, 6 Aug 2026 19:46:59 +0300 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V4 01/14] i3c: master: Fix recursive locking during device registration To: CC: Alexandre Belloni , , , References: <20260806131857.119830-1-adrian.hunter@intel.com> <20260806131857.119830-2-adrian.hunter@intel.com> <20260806133914.EDA761F000E9@smtp.kernel.org> Content-Language: en-US From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: c/o Alberga Business Park, 6 krs, Bertel Jungin Aukio 5, 02600 Espoo, Business Identity Code: 0357606 - 4, Domiciled in Helsinki In-Reply-To: <20260806133914.EDA761F000E9@smtp.kernel.org> X-ClientProxiedBy: DUZPR01CA0294.eurprd01.prod.exchangelabs.com (2603:10a6:10:4b7::13) To IA1PR11MB7198.namprd11.prod.outlook.com (2603:10b6:208:419::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA1PR11MB7198:EE_|BL4PR11MB8869:EE_ X-MS-Office365-Filtering-Correlation-Id: 1fc37602-d73e-449b-5193-08def3da5795 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|1800799024|376014|11063799006|56012099006|10067099003|6133799003|18002099003|22082099003|4143699003; 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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-i3c" Errors-To: linux-i3c-bounces+linux-i3c=archiver.kernel.org@lists.infradead.org On 06/08/2026 16:39, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: > > New issues: > - [High] Dropping the bus maintenance lock around device_register() exposes the I3C device descriptor to concurrent Use-After-Free. > > Pre-existing issues: > - [High] Unbalanced fwnode reference count decrement in i3c_device_release() leads to Use-After-Free. > -- > > --- Patch [1]: [PATCH V4 01/14] i3c: master: Fix recursive locking during device registration --- > commit b31a8482aa2ea710ccc853d0c74b77edebb131ff > Author: Adrian Hunter > Date: Thu Aug 6 13:18:44 2026 +0000 > > i3c: master: Fix recursive locking during device registration > > This commit addresses a recursive locking lockdep warning by decoupling > device creation from registration. It collects newly populated devices into a > temporary list under the maintenance lock, then releases the lock prior to > invoking device_register() to prevent probe deadlocks. Finally, the lock is > re-acquired to clean up any devices that failed registration. > >> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c >> --- a/drivers/i3c/master.c >> +++ b/drivers/i3c/master.c >> @@ -2104,25 +2113,37 @@ i3c_master_register_new_i3c_devs(struct i3c_master_controller *master) > > [ ... ] > >> + list_add_tail(&desc->dev->node, &i3c_unreg_devs); >> + } >> + >> + i3c_bus_maintenance_unlock(&master->bus); >> + >> + list_for_each_entry_safe(i3cdev, tmp, &i3c_unreg_devs, node) { >> + ret = device_register(&i3cdev->dev); > > [Severity: High] > Does dropping the bus maintenance lock around device_register() expose the > I3C device descriptor to a concurrent use-after-free? > > During registration, the driver core can call subsystem functions like > i3c_device_match(), which read i3cdev->desc locklessly: > > drivers/i3c/master.c:i3c_device_match() { > ... > if (i3cdev->desc && i3cdev->desc->boardinfo) > static_addr_method = i3cdev->desc->boardinfo->static_addr_method; The fix is in patch 7 "i3c: master: Fix potential UAF in i3c_device_match()" > ... > } > > Concurrently, an I3C Hot-Join or sysfs-triggered Dynamic Address Assignment > (DAA) could execute i3c_master_do_daa(), take the i3c_bus_maintenance_lock, > and call __i3c_master_add_i3c_dev_locked(). If DAA detects the device as a > duplicate, it replaces the descriptor and frees the old one: > > drivers/i3c/master.c:__i3c_master_add_i3c_dev_locked() { > ... > i3c_master_detach_i3c_dev(olddev); > i3c_master_free_i3c_dev(olddev); > ... > } > > If the registering thread is actively evaluating i3cdev->desc when this > happens, will it lead to memory corruption when reading fields like > desc->boardinfo? > >> + if (ret) >> + dev_err(&master->dev, "Failed to add I3C device (err = %d)\n", ret); >> + else >> + list_del_init(&i3cdev->node); >> + } >> + >> + i3c_bus_maintenance_lock(&master->bus); >> + >> + list_for_each_entry_safe(i3cdev, tmp, &i3c_unreg_devs, node) { >> + list_del(&i3cdev->node); >> + desc = i3cdev->desc; >> + i3cdev->desc = NULL; >> + put_device(&i3cdev->dev); > > [Severity: High] > This is a pre-existing issue, but does this error path cause an unbalanced > fwnode reference count decrement leading to a use-after-free? > > During device initialization, device_set_node() assigns the fwnode without > incrementing its reference count: > > drivers/i3c/master.c:i3c_master_register_new_i3c_devs() { > ... > if (desc->boardinfo) > device_set_node(&desc->dev->dev, desc->boardinfo->fwnode); > ... > } > > However, when put_device() is called here on registration failure, > the release function unconditionally drops a reference: > > drivers/i3c/master.c:i3c_device_release() { > ... > fwnode_handle_put(dev->fwnode); > ... > } > > Since the device object never acquired a reference to the boardinfo's fwnode, > will repeated registration failures or unbind operations drop the refcount > below zero, eventually prematurely freeing the fwnode? > >> + desc->dev = NULL; >> } >> + >> + i3c_bus_maintenance_unlock(&master->bus); >> } > -- linux-i3c mailing list linux-i3c@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-i3c