CVE-2022-49943 (GCVE-0-2022-49943)

Vulnerability from cvelistv5 – Published: 2025-06-18 10:59 – Updated: 2025-06-18 10:59
VLAI?
Title
USB: gadget: Fix obscure lockdep violation for udc_mutex
Summary
In 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.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: f44b0b95d50fffeca036e1ba36770390e0b519dd , < 1a065e4673cbdd9f222a05f85e17d78ea50c8d9c (git)
Affected: 2191c00855b03aa59c20e698be713d952d51fc18 , < 1016fc0c096c92dd0e6e0541daac7a7868169903 (git)
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    Linux Linux Affected: 5.19.7 , < 5.19.8 (semver)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/udc/core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "1a065e4673cbdd9f222a05f85e17d78ea50c8d9c",
              "status": "affected",
              "version": "f44b0b95d50fffeca036e1ba36770390e0b519dd",
              "versionType": "git"
            },
            {
              "lessThan": "1016fc0c096c92dd0e6e0541daac7a7868169903",
              "status": "affected",
              "version": "2191c00855b03aa59c20e698be713d952d51fc18",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/usb/gadget/udc/core.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "5.19.8",
              "status": "affected",
              "version": "5.19.7",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.19.8",
                  "versionStartIncluding": "5.19.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-06-18T10:59:58.516Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1a065e4673cbdd9f222a05f85e17d78ea50c8d9c"
        },
        {
          "url": "https://git.kernel.org/stable/c/1016fc0c096c92dd0e6e0541daac7a7868169903"
        }
      ],
      "title": "USB: gadget: Fix obscure lockdep violation for udc_mutex",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2022-49943",
    "datePublished": "2025-06-18T10:59:58.516Z",
    "dateReserved": "2025-06-18T10:57:27.381Z",
    "dateUpdated": "2025-06-18T10:59:58.516Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1"
}


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