drm/ttm: Always and only destroy bo->ttm_resv in ttm_bo_release_list

Fixes a use-after-free due to a race condition in
ttm_bo_cleanup_refs_and_unlock, which allows one task to reserve a BO
and destroy its ttm_resv while another task is waiting for it to signal
in reservation_object_wait_timeout_rcu.

v2:
* Always initialize bo->ttm_resv in ttm_bo_init_reserved
 (Christian König)

Fixes: 0d2bd2ae045d "drm/ttm: fix memory leak while individualizing BOs"
Reviewed-by: Chunming Zhou <david1.zhou@amd.com> # v1
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 4 insertions, 12 deletions

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 379ec41d2c69..c088703777e2 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -150,8 +150,7 @@ static void ttm_bo_release_list(struct kref *list_kref)
         ttm_tt_destroy(bo->ttm);
         atomic_dec(&bo->glob->bo_count);
         dma_fence_put(bo->moving);
-        if (bo->resv == &bo->ttm_resv)
-                reservation_object_fini(&bo->ttm_resv);
+        reservation_object_fini(&bo->ttm_resv);
         mutex_destroy(&bo->wu_mutex);
         if (bo->destroy)
                 bo->destroy(bo);
@@ -402,14 +401,11 @@ static int ttm_bo_individualize_resv(struct ttm_buffer_object *bo)
         if (bo->resv == &bo->ttm_resv)
                 return 0;
 
-        reservation_object_init(&bo->ttm_resv);
         BUG_ON(!reservation_object_trylock(&bo->ttm_resv));
 
         r = reservation_object_copy_fences(&bo->ttm_resv, bo->resv);
-        if (r) {
+        if (r)
                 reservation_object_unlock(&bo->ttm_resv);
-                reservation_object_fini(&bo->ttm_resv);
-        }
 
         return r;
 }
@@ -457,10 +453,8 @@ static void ttm_bo_cleanup_refs_or_queue(struct ttm_buffer_object *bo)
                 if (reservation_object_test_signaled_rcu(&bo->ttm_resv, true)) {
                         ttm_bo_del_from_lru(bo);
                         spin_unlock(&glob->lru_lock);
-                        if (bo->resv != &bo->ttm_resv) {
+                        if (bo->resv != &bo->ttm_resv)
                                 reservation_object_unlock(&bo->ttm_resv);
-                                reservation_object_fini(&bo->ttm_resv);
-                        }
 
                         ttm_bo_cleanup_memtype_use(bo);
                         return;
@@ -560,8 +554,6 @@ static int ttm_bo_cleanup_refs_and_unlock(struct ttm_buffer_object *bo,
         }
 
         ttm_bo_del_from_lru(bo);
-        if (!list_empty(&bo->ddestroy) && (bo->resv != &bo->ttm_resv))
-                reservation_object_fini(&bo->ttm_resv);
         list_del_init(&bo->ddestroy);
         kref_put(&bo->list_kref, ttm_bo_ref_bug);
 
@@ -1210,8 +1202,8 @@ int ttm_bo_init_reserved(struct ttm_bo_device *bdev,
                 lockdep_assert_held(&bo->resv->lock.base);
         } else {
                 bo->resv = &bo->ttm_resv;
-                reservation_object_init(&bo->ttm_resv);
         }
+        reservation_object_init(&bo->ttm_resv);
         atomic_inc(&bo->glob->bo_count);
         drm_vma_node_reset(&bo->vma_node);
         bo->priority = 0;