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)