usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

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Summary

CVECVE-2026-89738
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-11 20:20:04 UTC
Updated2026-09-11 20:20:04 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a self-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and at91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via mod_timer(). Both recover the same udc through container_of and dereference it on every iteration. Neither teardown path cancels this cycle. udc is devm-allocated, so it is freed after at91udc_remove() returns, and is likewise freed when probe fails and devres runs. A timer callback or work item that is pending or running at either point dereferences the freed udc. Add at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and from the usb_add_gadget_udc() failure path in probe; the remaining probe error paths fail before the timer is armed. timer_shutdown_sync() waits for a running callback and clears timer->function, which makes the work handler's mod_timer() a permanent no-op; cancel_work_sync() then drains any pending or running work whose re-arm attempt now does nothing. The timer must be shut down first, since cancelling the work alone would let the timer re-queue it. The guard mirrors probe: in IRQ mode the timer and work_struct are never initialized. This does not require a fault; a normal driver unbind can interleave with an already queued work item. This issue was found by an in-house static analysis tool.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 4037242c4f5ff77afe61bf07ca1e8a99490219e5 a2a602cb1e28d76a5398cec3fa21b0110385f501 git Not specified
CNA Linux Linux affected 4037242c4f5ff77afe61bf07ca1e8a99490219e5 51a311eb97e91ce1aed3005cb71ccb2e30f8cce8 git Not specified
CNA Linux Linux affected 4037242c4f5ff77afe61bf07ca1e8a99490219e5 557ef547d49ff5e6026a4d39bdd3113bd81d7688 git Not specified
CNA Linux Linux affected 4037242c4f5ff77afe61bf07ca1e8a99490219e5 c27d13ce4bab80fbdf6523928071b6c24b37606c git Not specified
CNA Linux Linux affected 2.6.36 Not specified
CNA Linux Linux unaffected 2.6.36 semver Not specified
CNA Linux Linux unaffected 6.12.109 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.50 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.4 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a2a602cb1e28d76a5398cec3fa21b0110385f501 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c27d13ce4bab80fbdf6523928071b6c24b37606c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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