net/mlx5e: Fix HV VHCA stats zero-sized buffer allocation

Summary

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Fix HV VHCA stats zero-sized buffer allocation mlx5e_hv_vhca_stats_create() is called from mlx5e_nic_enable(), before mlx5e_open(). At that point priv->stats_nch is still zero, because it is only ever incremented in mlx5e_channel_stats_alloc(), which is reached only from mlx5e_open_channel(). mlx5e_hv_vhca_stats_buf_size() therefore returns 0, and kvzalloc(0, GFP_KERNEL) returns ZERO_SIZE_PTR ((void *)16) rather than NULL. The "if (!buf)" guard does not catch this, and mlx5e_hv_vhca_stats_create() completes "successfully" with priv->stats_agent.buf set to ZERO_SIZE_PTR. Once channels are opened (priv->stats_nch > 0) and the hypervisor enables stats reporting, mlx5e_hv_vhca_stats_work() recomputes buf_len using the new non-zero stats_nch and calls memset(buf, 0, buf_len) on ZERO_SIZE_PTR, faulting at address 0x10. Allocate the buffer based on priv->max_nch, which is set in mlx5e_priv_init() and is the upper bound on stats_nch: • Add a separate helper mlx5e_hv_vhca_stats_buf_max_size() that returns sizeof(per_ring_stats) * max(max_nch, stats_nch), and use it for the kvzalloc() in mlx5e_hv_vhca_stats_create(). • Keep mlx5e_hv_vhca_stats_buf_size() (which returns based on stats_nch) for the worker's active payload size, so the wire format (block->rings = stats_nch) and the amount of data filled by mlx5e_hv_vhca_fill_stats() are unchanged. The max(max_nch, stats_nch) guard handles the rare case where mlx5e_attach_netdev() recomputes max_nch downward across a detach/resume cycle while priv->stats_nch persists (mlx5e_detach_netdev does not call mlx5e_priv_cleanup, so stats_nch is only reset when the netdev is destroyed). Without the guard, the worker could compute buf_len from stats_nch and overrun the smaller buffer allocated based on the reduced max_nch. Allocating a non-zero buffer also makes the kvzalloc() failure path in mlx5e_hv_vhca_stats_create() reachable for the first time: it returns early without (re)creating the agent. Clear priv->stats_agent.{agent,buf} in mlx5e_hv_vhca_stats_destroy() after freeing them, so that if a later create() bails out on this path, a subsequent teardown does not double-free the stale agent/buffer left from a previous enable/disable cycle. This mirrors the existing mlx5e pattern of preallocating arrays of size max_nch (e.g. priv->channel_stats) and lazily populating entries up to stats_nch on demand.

Timeline

1. Aug 15, 2026, 5:55 AM UTCCVE published
2. Oct 16, 2026, 6:47 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 16, 2026, 6:55 PM UTCRecord last updated

Affected versions

• Linux Linux

  From fa691d0c9c0812b9045f3a9420862e47b3b92518 · fixed in 3b3a552cf88e10bb7bda88b29cf1fd8267043d50; From fa691d0c9c0812b9045f3a9420862e47b3b92518 · fixed in 5b927dcec5f1087942bf123a82e64a3f66475f01; From fa691d0c9c0812b9045f3a9420862e47b3b92518 · fixed in 22c1d5ecccf92c849bdca1556179aafc95794baf; From fa691d0c9c0812b9045f3a9420862e47b3b92518 · fixed in 420aabb32da4381d8d7cdcaa6a77fad9eaceb0a4; From fa691d0c9c0812b9045f3a9420862e47b3b92518 · fixed in abc4c56427f144c96b2827a4db3b90eb5b7349a2; From fa691d0c9c0812b9045f3a9420862e47b3b92518 · fixed in 25f6b929c7e379cbea7cb8caa67b49b2d1efae17

• Linux Linux

  5.17

• KernelLinux

  From 5.17.0 · fixed in 6.1.178; From 6.2.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5

References 6