Linux Kernel amdgpu CVE-2026-53293

The amdgpu kernel DRM driver (CPE: cpe:2.3:a:linux:linux:*) exposes device information via the AMDGPU_INFO_READ_MMR_REG ioctl. This code path coordinates access using two synchronisation primitives: a reset semaphore (protecting GPU reset state) and an mm_lock (protecting memory-map state). CWE-667 (Improper Locking) covers three specific issues here: (1) the acquisition order of these primitives was reversed, causing copy_to_user() - a sleeping, preemptible operation - to execute while the mm_lock was held, violating kernel locking discipline; (2) kmalloc-style memory allocation was performed while the reset semaphore was held, a situation that can cause AB-BA deadlock under memory pressure; and (3) down_read_trylock() was used, meaning if a GPU reset was in progress the path would proceed without waiting, leading to use-under-reset conditions. The fix, cherry-picked from upstream commit 361b6e6b303d4b691f6c5974d3eaab67ca6dd90e, reorders lock acquisition, defers allocation outside the semaphore scope, and replaces trylock with a blocking down_read.