In the Linux kernel, the following vulnerability has been resolved: drm/amdkfd: Avoid integer underflow in EOP ring size calculation. The low 6 bits of cp_hqd_eop_control store the base-2 logarithm of the EOP ring size

Overview

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

drm/amdkfd: Avoid integer underflow in EOP ring size calculation.

The low 6 bits of cp_hqd_eop_control store the base-2 logarithm of the EOP ring size. This was calculated as

order_base_2(q->eop_ring_buffer_size / 4) - 1

But order_base_2 can in theory return 0, so this could underflow (although in practice the ring buffer size cannot be less than 4096).

Change this to

order_base_2(q->eop_ring_buffer_size / 8)

using properties of logarithms.

Also add to the above comment to make the mathematics more clear.

(cherry picked from commit f0f43fcf8b2b3a924cad9444340921c96ed5f634)

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Low · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · updated 2026-10-17 · vex