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CVE-2026-31726

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

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected 1444e0568bc2c70868e7b8da5b46fc2252acc3f5 before 0c00ec409d7b2bce3fcac73188b79a141db7cfda; affected 4962e5a2f301d24953f17d6748d986e21566abe1 before d92d1532e05b1b31d36d48765e43bf73d793d19f; affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 before 0587de744615628c38e33ddc1601160a5ea8c50a; affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 before c78e463ee134b4669579d453c81ae00795e4c19a; affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 before 8a1128d604c360eca135f15b882b70256a522145; affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 before 1aa9356881ee4ed414bf72d0c56d915492cb5345; affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 before c038ba56b92e410d1caec22b2dc68780a0b42091; affected b81ac4395bbeaf36e078dea1a48c02dd97b76235 before eba2936bbe6b752a31725a9eb5c674ecbf21ee7d; affected e10735ce87502b07e171727e574afdd6c0890a08; affected 5.10.117 before 5.10.253; affected 5.15.41 before 5.15.203; affected 5.17.9 before 5.18
Linux / Linuxaffected 5.18; unaffected 0 before 5.18; unaffected 5.10.253 through 5.10.*; unaffected 5.15.203 through 5.15.*; unaffected 6.1.168 through 6.1.*; unaffected 6.6.134 through 6.6.*; unaffected 6.12.81 through 6.12.*; unaffected 6.18.22 through 6.18.*; unaffected 6.19.12 through 6.19.*; unaffected 7.0 through *

CWE

No CWE identifiers supplied.

References