CVE-2026-72342

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

net/mlx5e: Fix HV VHCA stats agent registration race

mlx5ehvvhcastatscreate() registers the stats agent through mlx5hvvhcaagentcreate(). The helper publishes the agent in hvvhca->agents[type] under agentslock 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 mlx5ehvvhcastatscontrol(). That callback may either:

• call canceldelayedworksync(&priv->statsagent.work), or
• call queuedelayedwork(priv->wq, &sagent->work, sagent->delay).

However, the delayedwork and priv->statsagent.agent are only initialized after mlx5hvvhcaagentcreate() 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 delayedwork whose timer.function is NULL. queuedelayedwork() calls addtimer() unconditionally, so when the timer expires the timer softirq invokes a NULL function pointer.
• Re-initialize the timer later through INITDELAYEDWORK() 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, mlx5ehvvhcastatswork() reads sagent->agent (NULL) and dereferences it inside mlx5hvvhcaagentwrite().

Fix this by:

• Initializing priv->statsagent.work before invoking mlx5hvvhcaagent_create(), so the work is always in a valid state when the control callback observes it.
• Adding a struct mlx5hvvhcaagent **ctxupdate out-parameter to mlx5hvvhcaagentcreate(). The helper writes the agent pointer to *ctxupdate before publishing into hvvhca->agents[] and triggering the agentsupdate flow, so any callback subsequently invoked from that flow already sees a valid priv->statsagent.agent. This avoids having the control callback participate in agent initialization.

While at it, access priv->statsagent.agent with READONCE()/WRITEONCE() for the cross-CPU access with the worker, and clear priv->statsagent.buf on the agent_create() failure path.