[PATCH 4.19 091/103] drm/nouveau/mmu: qualify vmm during dtor

[Greg Kroah-Hartman]

From: Jon Derrick <jonathan.derrick@xxxxxxxxx>

commit 15516bf9abaa41421a6ded79a5a2fee86f9594e5 upstream.

If the BAR initialization failed it may leave the vmm structure in an
unitialized state, leading to a null-pointer-dereference when the vmm is
dereferenced during teardown.

Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
Signed-off-by: Ben Skeggs <bskeggs@xxxxxxxxxx>
Signed-off-by: Sushma Kalakota <sushmax.kalakota@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmm.c
@@ -1423,7 +1423,7 @@ nvkm_vmm_get(struct nvkm_vmm *vmm, u8 pa
 void
 nvkm_vmm_part(struct nvkm_vmm *vmm, struct nvkm_memory *inst)
 {
-	if (inst && vmm->func->part) {
+	if (inst && vmm && vmm->func->part) {
 		mutex_lock(&vmm->mutex);
 		vmm->func->part(vmm, inst);
 		mutex_unlock(&vmm->mutex);