CVE-2026-74713vhost_iotlb: bound map allocation in add_range

Official description

In the Linux kernel, the following vulnerability has been resolved: vhost_iotlb: bound map allocation in add_range vhost_iotlb_add_range_ctx() only retires an old entry when the table has a non-zero limit, has exactly reached that limit and has VHOST_IOTLB_FLAG_RETIRE set. Non-retiring tables can keep allocating entries after reaching their configured limit. Existing vhost devices allocate their IOTLB with max_iotlb_entries from vhost.c, which defaults to 2048 and is tunable by module parameter. Use the caller-provided limit at the allocation point instead of adding a separate default in the common IOTLB helper, and reject non-positive values in vhost paths that can report an error. Other vhost IOTLB users should not create zero-limit tables when entries can be populated from userspace or guest-controlled requests. Add caller-side max_iotlb_entries parameters for mlx5 vDPA, VDUSE and vhost-vDPA. Reject non-positive VDUSE and vhost-vDPA values, and require at least two entries for vdpa_sim and mlx5 vDPA paths that install full-range mappings, since those mappings are split into two IOTLB entries. Handle full-range mappings in the common helper by checking that the IOTLB can hold both split entries before inserting the first half. This avoids returning an error after leaving a half mapping behind. When the table is full, keep the existing retire behavior for retiring tables and return -ENOSPC for non-retiring tables. Reuse the retired map node instead of freeing it and allocating a replacement, so a stream of IOTLB updates cannot keep forcing GFP_ATOMIC allocations after the table has reached its limit. If a zero-limit IOTLB still reaches the common helper, treat it as a configuration error and return -EINVAL. I found this bug myself, though the patch was written with AI assistance.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/91d3f1fcb8f7109f18d46a7366bb8202ac4b4456
• https://git.kernel.org/stable/c/96da3e1439e7d689eea09fc9b6227fbab5b88ac3
• https://git.kernel.org/stable/c/eb70200e34772572ad08e99291b08afea6522111
• https://git.kernel.org/stable/c/b57164cdddb46924ff9fa191b727ca097744de88
• https://git.kernel.org/stable/c/ae128dd19040ee06a4f8143c7ced4d18080d7a9a
• https://git.kernel.org/stable/c/1ed35ac7f3fe2b4396bdd29ac3a7f0ebc0829e94