CyberRota Analysis
AI-GeneratedThe vulnerability affects the Linux kernel's amdgpu driver, specifically in the handling of device core dumps, where improper locking mechanisms can lead to potential recursive locking scenarios. This flaw could result in a deadlock situation when multiple buffer objects (BOs) share a reservation, causing system instability and flooding the kernel ring buffer with warnings. Organizations utilizing Linux systems with AMD GPUs should prioritize patching this vulnerability to ensure system reliability and prevent performance degradation.
Original NVD Description
In the Linux kernel, the following vulnerability has been resolved: drm/amdgpu: fix recursive ww_mutex acquire in amdgpu_devcoredump_format When dumping IB contents from a hung job, amdgpu_devcoredump_format() acquired the VM root PD's reservation via amdgpu_vm_lock_by_pasid() and then, for each IB, called amdgpu_bo_reserve() on the BO backing the IB. Both reservations are reservation_ww_class_mutex objects and neither used a ww_acquire_ctx, which trips lockdep: WARNING: possible recursive locking detected -------------------------------------------- kworker/u128:0 is trying to acquire lock: ffff88838b16e1f0 (reservation_ww_class_mutex){+.+.}-{4:4}, at: amdgpu_devcoredump_format+0x1594/0x23f0 [amdgpu] but task is already holding lock: ffff8882f82681f0 (reservation_ww_class_mutex){+.+.}-{4:4}, at: amdgpu_devcoredump_format+0x1594/0x23f0 [amdgpu] Possible unsafe locking scenario: CPU0 ---- lock(reservation_ww_class_mutex); lock(reservation_ww_class_mutex); *** DEADLOCK *** May be due to missing lock nesting notation Workqueue: events_unbound amdgpu_devcoredump_deferred_work [amdgpu] Call Trace: __ww_mutex_lock.constprop.0 ww_mutex_lock amdgpu_bo_reserve amdgpu_devcoredump_format+0x1594 [amdgpu] amdgpu_devcoredump_deferred_work+0xea [amdgpu] The two reservations are on different BOs in the captured trace, so the splat is a lockdep-correctness warning, not an observed deadlock. It becomes a real self-deadlock whenever the IB BO shares its dma_resv with the root PD (the always-valid case, see amdgpu_vm_is_bo_always_valid()): amdgpu_bo_reserve(abo) re-acquires the same ww_mutex without a ticket and blocks forever. With amdgpu.gpu_recovery=0 the timeout handler refires every ~2 s and each invocation produces this splat, drowning the kernel ring buffer. Now that amdgpu_vm_lock_by_pasid() takes a drm_exec context, move the IB dumping into a separate helper that locks the root PD and every IB BO together in a single drm_exec ticket. DRM_EXEC_IGNORE_DUPLICATES handles IB BOs that share a dma_resv (e.g. always-valid BOs, or two IBs backed by the same BO). Every lock is now a top-level acquire under one ww_acquire_ctx, so the recursive ww_mutex condition is gone, and the per-IB amdgpu_bo_reserve()/amdgpu_bo_unref() dance -- including a BO refcount leak on the amdgpu_bo_reserve() failure path -- is removed. (cherry picked from commit d6bf4242731219ee08ce54c365631e395486651e)