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

vsock/virtio: fix potential underflow in virtio_transport_get_credit()

The credit calculation in virtio_transport_get_credit() uses unsigned
arithmetic:

ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);

If the peer shrinks its advertised buffer (peer_buf_alloc) while bytes
are in flight, the subtraction can underflow and produce a large
positive value, potentially allowing more data to be queued than the
peer can handle.

Reuse virtio_transport_has_space() which already handles this case and
add a comment to make it clear why we are doing that.

[Stefano: use virtio_transport_has_space() instead of duplicating the code]
[Stefano: tweak the commit message]

References

• https://nvd.nist.gov/vuln/detail/CVE-2026-23069
• https://git.kernel.org/stable/c/02f9af192b98d15883c70dd41ac76d1b0217c899
• https://git.kernel.org/stable/c/3ef3d52a1a9860d094395c7a3e593f3aa26ff012
• https://git.kernel.org/stable/c/d05bc313788f0684b27f0f5b60c52a844669b542
• https://git.kernel.org/stable/c/ec0f1b3da8061be3173d1c39faaf9504f91942c3
• https://git.kernel.org/stable/c/d96de882d6b99955604669d962ae14e94b66a551