CVE-2021-4460: 
Linux Kernel vulnerability analysis and mitigation

CVE-2021-4460 affects the Linux kernel and involves a shift-out-of-bounds warning in the drm/amdkfd component. The vulnerability was published on October 1, 2025, and affects various Linux kernel versions (NVD).

The vulnerability occurs when getnumsdmaqueues or getnumxgmisdmaqueues is 0, resulting in a shift operation where the number of bits shifted equals the number of bits in the operand. This behavior is undefined. The fix involves setting numsdmaqueues or numxgmisdmaqueues to ULLONG_MAX if the count is greater than or equal to the number of bits in the operand (Ubuntu).

The vulnerability affects the Linux kernel's AMD Kernel Fusion Driver (AMDKFD) component, potentially leading to undefined behavior in systems using this driver. Several Ubuntu Linux distributions required patches, including focal (20.04 LTS) which was fixed in version 5.4.0-77.86 (Ubuntu).

The issue has been fixed in various Linux kernel versions. Ubuntu has released patches for affected systems, particularly in the focal (20.04 LTS) release with version 5.4.0-77.86 and bionic (18.04 LTS) with version 5.4.0-77.86~18.04.1 (Ubuntu).