usb: gadget: uvc: fix NULL pointer dereference during unbind race

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Summary

CVECVE-2026-31726
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 15:16:35 UTC
Updated2026-05-07 16:26:18 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000240000 probability, percentile 0.068060000 (date 2026-05-05)

Problem Types: CWE-476

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1444e0568bc2c70868e7b8da5b46fc2252acc3f5 0c00ec409d7b2bce3fcac73188b79a141db7cfda git Not specified
CNA Linux Linux affected 4962e5a2f301d24953f17d6748d986e21566abe1 d92d1532e05b1b31d36d48765e43bf73d793d19f git Not specified
CNA Linux Linux affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 0587de744615628c38e33ddc1601160a5ea8c50a git Not specified
CNA Linux Linux affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 c78e463ee134b4669579d453c81ae00795e4c19a git Not specified
CNA Linux Linux affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 8a1128d604c360eca135f15b882b70256a522145 git Not specified
CNA Linux Linux affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 1aa9356881ee4ed414bf72d0c56d915492cb5345 git Not specified
CNA Linux Linux affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 c038ba56b92e410d1caec22b2dc68780a0b42091 git Not specified
CNA Linux Linux affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 eba2936bbe6b752a31725a9eb5c674ecbf21ee7d git Not specified
CNA Linux Linux affected e10735ce87502b07e171727e574afdd6c0890a08 git Not specified
CNA Linux Linux affected 5.18 Not specified
CNA Linux Linux unaffected 5.18 semver Not specified
CNA Linux Linux unaffected 5.10.253 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.203 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.168 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.134 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.81 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.22 6.18.* semver Not specified
CNA Linux Linux unaffected 6.19.12 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1aa9356881ee4ed414bf72d0c56d915492cb5345 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/0c00ec409d7b2bce3fcac73188b79a141db7cfda 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/8a1128d604c360eca135f15b882b70256a522145 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/c78e463ee134b4669579d453c81ae00795e4c19a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/0587de744615628c38e33ddc1601160a5ea8c50a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/d92d1532e05b1b31d36d48765e43bf73d793d19f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/eba2936bbe6b752a31725a9eb5c674ecbf21ee7d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/c038ba56b92e410d1caec22b2dc68780a0b42091 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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