CVE-2026-99147

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

drm/exec: don't immediately add prelocked obj to array of locked objs

When a contention is detected the drm exec object grabs a reference to the contended object, unlocks all other objects and pre-locks the contended one before anything else.

The problem is that it is possible that this pre-locked object was about to be destroyed and drm exec is now holding the last reference to it.

So we never actually see this pre-locked object again to be explicitly locked and so also never reserve a slot for a dma fence object on it.

Should the driver now use drm exec for each locked object() to add a new fence to all locked objects we eventually see a warning or even a BUG ON() to prevent random memory corruption.

Fix this by keeping the prelocked object out of the array of locked objs until it was explicitly mentioned by the driver again.

If the prelocked object is never mentioned again by the driver just unlock and drop the reference at the end of the locking loop.