CVE-2026-97994

Summary

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

vhost/vdpa: reject VRING_NUM larger than device max

vhost_vring_set_num() accepts any non-zero power-of-two queue size that fits in 16 bits. vhost-vdpa then passes that value to set_vq_num() without comparing it with get_vq_num_max().

A process with access to /dev/vhost-vdpa-* can therefore configure a queue larger than the device advertises. With vdpa_sim, the worker can walk descriptors beyond the mapped descriptor ring. KASAN reports a 16-byte out-of-bounds read, corresponding to one vring_desc, in the vringh IOTLB path:

BUG: KASAN: out-of-bounds in _copy_from_iter Read of size 16 copy_from_iotlb copydesc_iotlb vringh_getdesc_iotlb vdpasim_net_work

Cache get_vq_num_max() immediately after reset. Some backends derive it from writable queue-size state, so querying it after SET_NUM may return the current size instead of the device capability. Invalidate the cached value before reset so a failed reset leaves SET_NUM disabled.

For VHOST_SET_VRING_NUM, copy the complete vring state once and use the same index and size for validation, vq->num, and set_vq_num(). This ensures that validation and use operate on the same copied values.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/1d09201d81b7d3e276860cc7b7dbf6c6cbe8e9b4
• https://git.kernel.org/stable/c/68232102f20fc961327fb9e0f605a7eaadf030a9
• https://git.kernel.org/stable/c/59522639a7d71cff4e20d594d0b9ea30dd0c77e0
• https://git.kernel.org/stable/c/ccb1dc7c527f8c925925cf92afc76ae590dac311

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