From: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> [ Upstream commit bc1922e5d349db4be14c55513102c024c2ae8a50 ] The vma destruction code was using an unlocked advisory check for drm_mm_node_allocated() to avoid racing with eviction code unbinding the vma. This is very fragile and prohibits the dereference of non-refcounted pointers of dying vmas after a call to __i915_vma_unbind(). It also prohibits the dereference of vma->obj of refcounted pointers of dying vmas after a call to __i915_vma_unbind(), since even if a refcount is held on the vma, that won't guarantee that its backing object doesn't get destroyed. So introduce an unbind under the vm mutex at object destroy time, removing all weak references of the vma and its object from the object vma list and from the vm bound list. Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20220127115622.302970-1-thomas.hellstrom@xxxxxxxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/gpu/drm/i915/gem/i915_gem_object.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c index 6fb9afb65034..5f48d5ea5c15 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c @@ -224,6 +224,12 @@ void __i915_gem_free_object(struct drm_i915_gem_object *obj) GEM_BUG_ON(vma->obj != obj); spin_unlock(&obj->vma.lock); + /* Verify that the vma is unbound under the vm mutex. */ + mutex_lock(&vma->vm->mutex); + atomic_and(~I915_VMA_PIN_MASK, &vma->flags); + __i915_vma_unbind(vma); + mutex_unlock(&vma->vm->mutex); + __i915_vma_put(vma); spin_lock(&obj->vma.lock); -- 2.35.1
