GHSA-6CPQ-CWGW-5G63
Vulnerability from github – Published: 2025-06-18 12:30 – Updated: 2025-11-14 21:30In the Linux kernel, the following vulnerability has been resolved:
USB: gadget: Fix obscure lockdep violation for udc_mutex
A recent commit expanding the scope of the udc_lock mutex in the gadget core managed to cause an obscure and slightly bizarre lockdep violation. In abbreviated form:
====================================================== WARNING: possible circular locking dependency detected 5.19.0-rc7+ #12510 Not tainted
udevadm/312 is trying to acquire lock: ffff80000aae1058 (udc_lock){+.+.}-{3:3}, at: usb_udc_uevent+0x54/0xe0
but task is already holding lock: ffff000002277548 (kn->active#4){++++}-{0:0}, at: kernfs_seq_start+0x34/0xe0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (kn->active#4){++++}-{0:0}: lock_acquire+0x68/0x84 __kernfs_remove+0x268/0x380 kernfs_remove_by_name_ns+0x58/0xac sysfs_remove_file_ns+0x18/0x24 device_del+0x15c/0x440
-> #2 (device_links_lock){+.+.}-{3:3}: lock_acquire+0x68/0x84 __mutex_lock+0x9c/0x430 mutex_lock_nested+0x38/0x64 device_link_remove+0x3c/0xa0 _regulator_put.part.0+0x168/0x190 regulator_put+0x3c/0x54 devm_regulator_release+0x14/0x20
-> #1 (regulator_list_mutex){+.+.}-{3:3}: lock_acquire+0x68/0x84 __mutex_lock+0x9c/0x430 mutex_lock_nested+0x38/0x64 regulator_lock_dependent+0x54/0x284 regulator_enable+0x34/0x80 phy_power_on+0x24/0x130 __dwc2_lowlevel_hw_enable+0x100/0x130 dwc2_lowlevel_hw_enable+0x18/0x40 dwc2_hsotg_udc_start+0x6c/0x2f0 gadget_bind_driver+0x124/0x1f4
-> #0 (udc_lock){+.+.}-{3:3}: __lock_acquire+0x1298/0x20cc lock_acquire.part.0+0xe0/0x230 lock_acquire+0x68/0x84 __mutex_lock+0x9c/0x430 mutex_lock_nested+0x38/0x64 usb_udc_uevent+0x54/0xe0
Evidently this was caused by the scope of udc_mutex being too large. The mutex is only meant to protect udc->driver along with a few other things. As far as I can tell, there's no reason for the mutex to be held while the gadget core calls a gadget driver's ->bind or ->unbind routine, or while a UDC is being started or stopped. (This accounts for link #1 in the chain above, where the mutex is held while the dwc2_hsotg_udc is started as part of driver probing.)
Gadget drivers' ->disconnect callbacks are problematic. Even though usb_gadget_disconnect() will now acquire the udc_mutex, there's a window in usb_gadget_bind_driver() between the times when the mutex is released and the ->bind callback is invoked. If a disconnect occurred during that window, we could call the driver's ->disconnect routine before its ->bind routine. To prevent this from happening, it will be necessary to prevent a UDC from connecting while it has no gadget driver. This should be done already but it doesn't seem to be; currently usb_gadget_connect() has no check for this. Such a check will have to be added later.
Some degree of mutual exclusion is required in soft_connect_store(), which can dereference udc->driver at arbitrary times since it is a sysfs callback. The solution here is to acquire the gadget's device lock rather than the udc_mutex. Since the driver core guarantees that the device lock is always held during driver binding and unbinding, this will make the accesses in soft_connect_store() mutually exclusive with any changes to udc->driver.
Lastly, it turns out there is one place which should hold the udc_mutex but currently does not: The function_show() routine needs protection while it dereferences udc->driver. The missing lock and unlock calls are added.
{
"affected": [],
"aliases": [
"CVE-2022-49943"
],
"database_specific": {
"cwe_ids": [
"CWE-667"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-06-18T11:15:21Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nUSB: gadget: Fix obscure lockdep violation for udc_mutex\n\nA recent commit expanding the scope of the udc_lock mutex in the\ngadget core managed to cause an obscure and slightly bizarre lockdep\nviolation. In abbreviated form:\n\n======================================================\nWARNING: possible circular locking dependency detected\n5.19.0-rc7+ #12510 Not tainted\n------------------------------------------------------\nudevadm/312 is trying to acquire lock:\nffff80000aae1058 (udc_lock){+.+.}-{3:3}, at: usb_udc_uevent+0x54/0xe0\n\nbut task is already holding lock:\nffff000002277548 (kn-\u003eactive#4){++++}-{0:0}, at: kernfs_seq_start+0x34/0xe0\n\nwhich lock already depends on the new lock.\n\nthe existing dependency chain (in reverse order) is:\n\n-\u003e #3 (kn-\u003eactive#4){++++}-{0:0}:\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 lock_acquire+0x68/0x84\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 __kernfs_remove+0x268/0x380\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 kernfs_remove_by_name_ns+0x58/0xac\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 sysfs_remove_file_ns+0x18/0x24\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 device_del+0x15c/0x440\n\n-\u003e #2 (device_links_lock){+.+.}-{3:3}:\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 lock_acquire+0x68/0x84\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 __mutex_lock+0x9c/0x430\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 mutex_lock_nested+0x38/0x64\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 device_link_remove+0x3c/0xa0\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 _regulator_put.part.0+0x168/0x190\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 regulator_put+0x3c/0x54\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 devm_regulator_release+0x14/0x20\n\n-\u003e #1 (regulator_list_mutex){+.+.}-{3:3}:\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 lock_acquire+0x68/0x84\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 __mutex_lock+0x9c/0x430\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 mutex_lock_nested+0x38/0x64\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 regulator_lock_dependent+0x54/0x284\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 regulator_enable+0x34/0x80\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 phy_power_on+0x24/0x130\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 __dwc2_lowlevel_hw_enable+0x100/0x130\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 dwc2_lowlevel_hw_enable+0x18/0x40\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 dwc2_hsotg_udc_start+0x6c/0x2f0\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 gadget_bind_driver+0x124/0x1f4\n\n-\u003e #0 (udc_lock){+.+.}-{3:3}:\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 __lock_acquire+0x1298/0x20cc\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 lock_acquire.part.0+0xe0/0x230\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 lock_acquire+0x68/0x84\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 __mutex_lock+0x9c/0x430\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 mutex_lock_nested+0x38/0x64\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 usb_udc_uevent+0x54/0xe0\n\nEvidently this was caused by the scope of udc_mutex being too large.\nThe mutex is only meant to protect udc-\u003edriver along with a few other\nthings. As far as I can tell, there\u0027s no reason for the mutex to be\nheld while the gadget core calls a gadget driver\u0027s -\u003ebind or -\u003eunbind\nroutine, or while a UDC is being started or stopped. (This accounts\nfor link #1 in the chain above, where the mutex is held while the\ndwc2_hsotg_udc is started as part of driver probing.)\n\nGadget drivers\u0027 -\u003edisconnect callbacks are problematic. Even though\nusb_gadget_disconnect() will now acquire the udc_mutex, there\u0027s a\nwindow in usb_gadget_bind_driver() between the times when the mutex is\nreleased and the -\u003ebind callback is invoked. If a disconnect occurred\nduring that window, we could call the driver\u0027s -\u003edisconnect routine\nbefore its -\u003ebind routine. To prevent this from happening, it will be\nnecessary to prevent a UDC from connecting while it has no gadget\ndriver. This should be done already but it doesn\u0027t seem to be;\ncurrently usb_gadget_connect() has no check for this. Such a check\nwill have to be added later.\n\nSome degree of mutual exclusion is required in soft_connect_store(),\nwhich can dereference udc-\u003edriver at arbitrary times since it is a\nsysfs callback. The solution here is to acquire the gadget\u0027s device\nlock rather than the udc_mutex. Since the driver core guarantees that\nthe device lock is always held during driver binding and unbinding,\nthis will make the accesses in soft_connect_store() mutually exclusive\nwith any changes to udc-\u003edriver.\n\nLastly, it turns out there is one place which should hold the\nudc_mutex but currently does not: The function_show() routine needs\nprotection while it dereferences udc-\u003edriver. The missing lock and\nunlock calls are added.",
"id": "GHSA-6cpq-cwgw-5g63",
"modified": "2025-11-14T21:30:27Z",
"published": "2025-06-18T12:30:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2022-49943"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1016fc0c096c92dd0e6e0541daac7a7868169903"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1a065e4673cbdd9f222a05f85e17d78ea50c8d9c"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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