High [CVE-2026-63879] fix amdgpu_hmm_range_get_pages

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix amdgpu_hmm_range_get_pages The notifier sequence must only be read once or otherwise we could work with invalid pages.

While at it also fix the coding style, e.g. drop the pre-initialized return value and use the common define for 2G range. (cherry picked from commit c08972f555945cda57b0adb72272a37910153390) A flaw was found in the Linux kernel, specifically within the `drm/amdgpu` component.

This vulnerability arises from incorrect handling of a notifier sequence in the `amdgpu_hmm_range_get_pages` function, where the sequence can be read more than once. This can lead to the system processing invalid memory pages, potentially resulting in system instability or crashes.

This vulnerability is rated as an Important impact for Red Hat Enterprise Linux because local authenticated users on systems with AMD graphics hardware can exploit improper memory page handling to compromise kernel memory integrity or cause a denial of service.

Although exploiting the flaw requires local system access and interaction with the amdgpu driver, administrative privileges are not needed to trigger the condition. Headless environments or systems running non-AMD graphics hardware do not load the affected module and are not exposed.

Red Hat severity: Important — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H).