Linux Kernel DRM Nouveau Tears Down the Fence Context Before Unsubscribing Channel-Kill Events, Creating a Use-After-Free Window

Status: NEW  |  Advisory ID: CVE-2026-89803

Key Details

What to Know

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

drm/nouveau: unsubscribe the channel-kill event before the fence context

nouveau_channel_del() tears the fence context down first and only drops

the channel-kill subscription later, in the middle of the nvif object

teardown:

if (chan->fence)

nouveau_fence(chan->cli->drm)->context_del(chan);

...

nvif_object_dtor(&chan->vram);

nvif_event_dtor(&chan->kill);

The subscribed handler is nouveau_channel_killed(), which calls

nouveau_channel_kill() and from there nouveau_fence_context_kill() on

chan->fence. A kill event delivered in that window takes fctx->lock and

walks fctx->pending on a fence context that context_del() has already

freed.

Nothing reaches this below Fermi today, because the subscription is

gated on FERMI_CHANNEL_GPFIFO and nothing kills a channel there. On

Fermi and newer the window is real but narrow, since a kill has to land

exactly while the channel is being destroyed. That is reason enough on

its own, which is why this carries a Fixes: tag. The last patch in this

series subscribes Tesla channels as well; nothing kills those today, so

it does not widen the exposure now, but it is the groundwork for a

recovery path that would, and the ordering is better fixed before that

lands than alongside it.

Drop the subscription before anything it depends on is torn down. (NVD)

References