avoid double drm_exec_fini() in userq validate

Summary

In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: avoid double drm_exec_fini() in userq validate When new_addition is true, amdgpu_userq_vm_validate() calls drm_exec_fini(&exec) before iterating over the collected HMM ranges and calling amdgpu_ttm_tt_get_user_pages(). If amdgpu_ttm_tt_get_user_pages() fails in that path, the code jumps to unlock_all and calls drm_exec_fini(&exec) a second time on the same exec object. drm_exec_fini() is not idempotent: it frees exec->objects and may also drop exec->contended and finalize the ww acquire context. Route that error path directly to the range cleanup once exec has already been finalized. Issue found using a prototype static analysis tool and confirmed by code review. (cherry picked from commit 2802952e4a07306da6ebe813ff1acacc5691851a) A flaw was found in the Linux kernel. A double free vulnerability exists in the `drm/amdgpu` component within the `userq validate` function. This issue arises because the `drm_exec_fini()` function is called twice on the same execution object, which is not designed to be idempotent. An attacker could potentially exploit this to cause a denial of service or lead to unpredictable system behavior. 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). Weakness: CWE-1341. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.