ghsa-p485-45xx-39cv
Vulnerability from github
Published
2025-06-18 12:30
Modified
2025-06-18 12:30
Details

In the Linux kernel, the following vulnerability has been resolved:

PM: hibernate: defer device probing when resuming from hibernation

syzbot is reporting hung task at misc_open() [1], for there is a race window of AB-BA deadlock which involves probe_count variable. Currently wait_for_device_probe() from snapshot_open() from misc_open() can sleep forever with misc_mtx held if probe_count cannot become 0.

When a device is probed by hub_event() work function, probe_count is incremented before the probe function starts, and probe_count is decremented after the probe function completed.

There are three cases that can prevent probe_count from dropping to 0.

(a) A device being probed stopped responding (i.e. broken/malicious hardware).

(b) A process emulating a USB device using /dev/raw-gadget interface stopped responding for some reason.

(c) New device probe requests keeps coming in before existing device probe requests complete.

The phenomenon syzbot is reporting is (b). A process which is holding system_transition_mutex and misc_mtx is waiting for probe_count to become 0 inside wait_for_device_probe(), but the probe function which is called from hub_event() work function is waiting for the processes which are blocked at mutex_lock(&misc_mtx) to respond via /dev/raw-gadget interface.

This patch mitigates (b) by deferring wait_for_device_probe() from snapshot_open() to snapshot_write() and snapshot_ioctl(). Please note that the possibility of (b) remains as long as any thread which is emulating a USB device via /dev/raw-gadget interface can be blocked by uninterruptible blocking operations (e.g. mutex_lock()).

Please also note that (a) and (c) are not addressed. Regarding (c), we should change the code to wait for only one device which contains the image for resuming from hibernation. I don't know how to address (a), for use of timeout for wait_for_device_probe() might result in loss of user data in the image. Maybe we should require the userland to wait for the image device before opening /dev/snapshot interface.

Show details on source website


{
  "affected": [],
  "aliases": [
    "CVE-2022-50202"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-06-18T11:15:50Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nPM: hibernate: defer device probing when resuming from hibernation\n\nsyzbot is reporting hung task at misc_open() [1], for there is a race\nwindow of AB-BA deadlock which involves probe_count variable. Currently\nwait_for_device_probe() from snapshot_open() from misc_open() can sleep\nforever with misc_mtx held if probe_count cannot become 0.\n\nWhen a device is probed by hub_event() work function, probe_count is\nincremented before the probe function starts, and probe_count is\ndecremented after the probe function completed.\n\nThere are three cases that can prevent probe_count from dropping to 0.\n\n  (a) A device being probed stopped responding (i.e. broken/malicious\n      hardware).\n\n  (b) A process emulating a USB device using /dev/raw-gadget interface\n      stopped responding for some reason.\n\n  (c) New device probe requests keeps coming in before existing device\n      probe requests complete.\n\nThe phenomenon syzbot is reporting is (b). A process which is holding\nsystem_transition_mutex and misc_mtx is waiting for probe_count to become\n0 inside wait_for_device_probe(), but the probe function which is called\n from hub_event() work function is waiting for the processes which are\nblocked at mutex_lock(\u0026misc_mtx) to respond via /dev/raw-gadget interface.\n\nThis patch mitigates (b) by deferring wait_for_device_probe() from\nsnapshot_open() to snapshot_write() and snapshot_ioctl(). Please note that\nthe possibility of (b) remains as long as any thread which is emulating a\nUSB device via /dev/raw-gadget interface can be blocked by uninterruptible\nblocking operations (e.g. mutex_lock()).\n\nPlease also note that (a) and (c) are not addressed. Regarding (c), we\nshould change the code to wait for only one device which contains the\nimage for resuming from hibernation. I don\u0027t know how to address (a), for\nuse of timeout for wait_for_device_probe() might result in loss of user\ndata in the image. Maybe we should require the userland to wait for the\nimage device before opening /dev/snapshot interface.",
  "id": "GHSA-p485-45xx-39cv",
  "modified": "2025-06-18T12:30:55Z",
  "published": "2025-06-18T12:30:55Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-50202"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/003a456ae6f70bb97e436e02fc5105be577c1570"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2f0e18e0db42f4f8bc87d3d98333680065ceeff8"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3c48d3067eaf878642276f053575a5c642600a50"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5a283b59bce72c05c60e9f0fa92a28b5b850d8bb"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8386c414e27caba8501119948e9551e52b527f59"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8c90947e5f1801e6c7120021c6ea0f3ad6a4eb91"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b8e1ae9433d7bd95f2dcc044a7a6f20a4c40d258"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f7042cf9dd40733f387b7cac021e626c74b8856f"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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