CVE-2026-31726 (GCVE-0-2026-31726)
Vulnerability from cvelistv5
Published
2026-05-01 14:14
Modified
2026-05-01 14:14
Severity ?
VLAI Severity ?
EPSS score ?
Summary
In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: uvc: fix NULL pointer dereference during unbind race
Commit b81ac4395bbe ("usb: gadget: uvc: allow for application to cleanly
shutdown") introduced two stages of synchronization waits totaling 1500ms
in uvc_function_unbind() to prevent several types of kernel panics.
However, this timing-based approach is insufficient during power
management (PM) transitions.
When the PM subsystem starts freezing user space processes, the
wait_event_interruptible_timeout() is aborted early, which allows the
unbind thread to proceed and nullify the gadget pointer
(cdev->gadget = NULL):
[ 814.123447][ T947] configfs-gadget.g1 gadget.0: uvc: uvc_function_unbind()
[ 814.178583][ T3173] PM: suspend entry (deep)
[ 814.192487][ T3173] Freezing user space processes
[ 814.197668][ T947] configfs-gadget.g1 gadget.0: uvc: uvc_function_unbind no clean disconnect, wait for release
When the PM subsystem resumes or aborts the suspend and tasks are
restarted, the V4L2 release path is executed and attempts to access the
already nullified gadget pointer, triggering a kernel panic:
[ 814.292597][ C0] PM: pm_system_irq_wakeup: 479 triggered dhdpcie_host_wake
[ 814.386727][ T3173] Restarting tasks ...
[ 814.403522][ T4558] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030
[ 814.404021][ T4558] pc : usb_gadget_deactivate+0x14/0xf4
[ 814.404031][ T4558] lr : usb_function_deactivate+0x54/0x94
[ 814.404078][ T4558] Call trace:
[ 814.404080][ T4558] usb_gadget_deactivate+0x14/0xf4
[ 814.404083][ T4558] usb_function_deactivate+0x54/0x94
[ 814.404087][ T4558] uvc_function_disconnect+0x1c/0x5c
[ 814.404092][ T4558] uvc_v4l2_release+0x44/0xac
[ 814.404095][ T4558] v4l2_release+0xcc/0x130
Address the race condition and NULL pointer dereference by:
1. State Synchronization (flag + mutex)
Introduce a 'func_unbound' flag in struct uvc_device. This allows
uvc_function_disconnect() to safely skip accessing the nullified
cdev->gadget pointer. As suggested by Alan Stern, this flag is protected
by a new mutex (uvc->lock) to ensure proper memory ordering and prevent
instruction reordering or speculative loads. This mutex is also used to
protect 'func_connected' for consistent state management.
2. Explicit Synchronization (completion)
Use a completion to synchronize uvc_function_unbind() with the
uvc_vdev_release() callback. This prevents Use-After-Free (UAF) by
ensuring struct uvc_device is freed after all video device resources
are released.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1444e0568bc2c70868e7b8da5b46fc2252acc3f5 Version: 4962e5a2f301d24953f17d6748d986e21566abe1 Version: b81ac4395bbeaf36e078dea1a48c02dd97b76235 Version: b81ac4395bbeaf36e078dea1a48c02dd97b76235 Version: b81ac4395bbeaf36e078dea1a48c02dd97b76235 Version: b81ac4395bbeaf36e078dea1a48c02dd97b76235 Version: b81ac4395bbeaf36e078dea1a48c02dd97b76235 Version: b81ac4395bbeaf36e078dea1a48c02dd97b76235 Version: e10735ce87502b07e171727e574afdd6c0890a08 |
||
{
"containers": {
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"programFiles": [
"drivers/usb/gadget/function/f_uvc.c",
"drivers/usb/gadget/function/uvc.h",
"drivers/usb/gadget/function/uvc_v4l2.c"
],
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"drivers/usb/gadget/function/uvc.h",
"drivers/usb/gadget/function/uvc_v4l2.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
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},
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"status": "unaffected",
"version": "0",
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},
{
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"status": "unaffected",
"version": "5.10.253",
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},
{
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},
{
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{
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},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: uvc: fix NULL pointer dereference during unbind race\n\nCommit b81ac4395bbe (\"usb: gadget: uvc: allow for application to cleanly\nshutdown\") introduced two stages of synchronization waits totaling 1500ms\nin uvc_function_unbind() to prevent several types of kernel panics.\nHowever, this timing-based approach is insufficient during power\nmanagement (PM) transitions.\n\nWhen the PM subsystem starts freezing user space processes, the\nwait_event_interruptible_timeout() is aborted early, which allows the\nunbind thread to proceed and nullify the gadget pointer\n(cdev-\u003egadget = NULL):\n\n[ 814.123447][ T947] configfs-gadget.g1 gadget.0: uvc: uvc_function_unbind()\n[ 814.178583][ T3173] PM: suspend entry (deep)\n[ 814.192487][ T3173] Freezing user space processes\n[ 814.197668][ T947] configfs-gadget.g1 gadget.0: uvc: uvc_function_unbind no clean disconnect, wait for release\n\nWhen the PM subsystem resumes or aborts the suspend and tasks are\nrestarted, the V4L2 release path is executed and attempts to access the\nalready nullified gadget pointer, triggering a kernel panic:\n\n[ 814.292597][ C0] PM: pm_system_irq_wakeup: 479 triggered dhdpcie_host_wake\n[ 814.386727][ T3173] Restarting tasks ...\n[ 814.403522][ T4558] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000030\n[ 814.404021][ T4558] pc : usb_gadget_deactivate+0x14/0xf4\n[ 814.404031][ T4558] lr : usb_function_deactivate+0x54/0x94\n[ 814.404078][ T4558] Call trace:\n[ 814.404080][ T4558] usb_gadget_deactivate+0x14/0xf4\n[ 814.404083][ T4558] usb_function_deactivate+0x54/0x94\n[ 814.404087][ T4558] uvc_function_disconnect+0x1c/0x5c\n[ 814.404092][ T4558] uvc_v4l2_release+0x44/0xac\n[ 814.404095][ T4558] v4l2_release+0xcc/0x130\n\nAddress the race condition and NULL pointer dereference by:\n\n1. State Synchronization (flag + mutex)\nIntroduce a \u0027func_unbound\u0027 flag in struct uvc_device. This allows\nuvc_function_disconnect() to safely skip accessing the nullified\ncdev-\u003egadget pointer. As suggested by Alan Stern, this flag is protected\nby a new mutex (uvc-\u003elock) to ensure proper memory ordering and prevent\ninstruction reordering or speculative loads. This mutex is also used to\nprotect \u0027func_connected\u0027 for consistent state management.\n\n2. Explicit Synchronization (completion)\nUse a completion to synchronize uvc_function_unbind() with the\nuvc_vdev_release() callback. This prevents Use-After-Free (UAF) by\nensuring struct uvc_device is freed after all video device resources\nare released."
}
],
"providerMetadata": {
"dateUpdated": "2026-05-01T14:14:26.882Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/0c00ec409d7b2bce3fcac73188b79a141db7cfda"
},
{
"url": "https://git.kernel.org/stable/c/d92d1532e05b1b31d36d48765e43bf73d793d19f"
},
{
"url": "https://git.kernel.org/stable/c/0587de744615628c38e33ddc1601160a5ea8c50a"
},
{
"url": "https://git.kernel.org/stable/c/c78e463ee134b4669579d453c81ae00795e4c19a"
},
{
"url": "https://git.kernel.org/stable/c/8a1128d604c360eca135f15b882b70256a522145"
},
{
"url": "https://git.kernel.org/stable/c/1aa9356881ee4ed414bf72d0c56d915492cb5345"
},
{
"url": "https://git.kernel.org/stable/c/c038ba56b92e410d1caec22b2dc68780a0b42091"
},
{
"url": "https://git.kernel.org/stable/c/eba2936bbe6b752a31725a9eb5c674ecbf21ee7d"
}
],
"title": "usb: gadget: uvc: fix NULL pointer dereference during unbind race",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-31726",
"datePublished": "2026-05-01T14:14:26.882Z",
"dateReserved": "2026-03-09T15:48:24.134Z",
"dateUpdated": "2026-05-01T14:14:26.882Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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