CVE-2026-72342

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

net/mlx5e: Fix HV VHCA stats agent registration race

mlx5e_hv_vhca_stats_create() registers the stats agent through

mlx5_hv_vhca_agent_create(). The helper publishes the agent in

hv_vhca->agents[type] under agents_lock and immediately schedules an

asynchronous control invalidation on the HV VHCA workqueue before

returning to mlx5e.

The asynchronous invalidation invokes the control agent's invalidate

callback, which reads the hypervisor control block and forwards the

command to mlx5e_hv_vhca_stats_control(). That callback may either:

- call cancel_delayed_work_sync(&priv->stats_agent.work), or

- call queue_delayed_work(priv->wq, &sagent->work, sagent->delay).

However, the delayed_work and priv->stats_agent.agent are only

initialized after mlx5_hv_vhca_agent_create() returns to mlx5e:

agent = mlx5_hv_vhca_agent_create(...); /* publish + invalidate */

...

priv->stats_agent.agent = agent; /* too late */

INIT_DELAYED_WORK(&priv->stats_agent.work, ...); /* too late */

If the asynchronous control path runs before the two assignments

above, it can:

- Operate on an uninitialized delayed_work whose timer.function is

NULL. queue_delayed_work() calls add_timer() unconditionally, so

when the timer expires the timer softirq invokes a NULL function

pointer.

- Re-initialize the timer later through INIT_DELAYED_WORK() while

the timer is already enqueued in the timer wheel, corrupting the

hlist (entry.pprev cleared while the previous bucket node still

points at this entry).

- When the worker eventually runs, mlx5e_hv_vhca_stats_work() reads

sagent->agent (NULL) and dereferences it inside

mlx5_hv_vhca_agent_write().

Fix this by:

- Initializing priv->stats_agent.work before invoking

mlx5_hv_vhca_agent_create(), so the work is always in a valid

state when the control callback observes it.

- Adding a struct mlx5_hv_vhca_agent **ctx_update out-parameter

to mlx5_hv_vhca_agent_create(). The helper writes the agent

pointer to *ctx_update before publishing into hv_vhca->agents[]

and triggering the agents_update flow, so any callback

subsequently invoked from that flow already sees a valid

priv->stats_agent.agent. This avoids having the control

callback participate in agent initialization.

While at it, access priv->stats_agent.agent with

READ_ONCE()/WRITE_ONCE() for the cross-CPU access with the worker, and

clear priv->stats_agent.buf on the agent_create() failure path.