CVE-2026-98859: HID: multitouch: stop the release timer from being rearmed on remove

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

HID: multitouch: stop the release timer from being rearmed on remove

mtremove() quiesces the sticky-finger timer before stopping the hardware:

timerdeletesync(&td->releasetimer);

sysfsremovegroup(&hdev->dev.kobj, &mtattributegroup); hidhwstop(hdev);

timerdeletesync() waits for a running callback and dequeues the timer, but it does not stop the timer from being armed again. The transport is still delivering reports at that point, and the report path rearms it:

if (app->quirks & MTQUIRKSTICKYFINGERS) { if (td->mtioflags & MTIOSLOTSMASK) modtimer(&td->releasetimer, jiffies + msecstojiffies(100));

A report that arrives after timerdeletesync() has returned therefore leaves the timer queued. td is allocated with devmkzalloc() against hdev->dev, so it is freed when the driver is unbound, after mtremove() returns. When the timer fires afterwards, mtexpiredtimeout() dereferences the freed td:

struct mtdevice td = timercontainerof(td, t, releasetimer); struct hiddevice hdev = td->hdev;

if (testandsetbitlock(MTIOFLAGSRUNNING, &td->mtioflags))

Simply moving the teardown after hidhwstop() does not fix this on its own, because mtexpiredtimeout() calls mtreleasecontacts(), which walks hdev->inputs; the timer still has to be quiesced before hidhwstop() tears the input devices down.

Use timershutdownsync() instead, which additionally makes any later modtimer() a no-op, so neither ordering constraint has to be traded off against the other. This is the final-teardown pattern the function was introduced for, and hid-wiimote already uses it for the same reason.