drm/nouveau: do not allow negative sizes for now

[Dan Carpenter]

Hello Maarten Lankhorst,

This is a semi-automatic email about new static checker warnings.

The patch 0108bc808107: "drm/nouveau: do not allow negative sizes for 
now" from Jul 7, 2013, leads to the following Smatch complaint:

drivers/gpu/drm/nouveau/nouveau_bo.c:222 nouveau_bo_new()
	 warn: variable dereferenced before check 'drm->client.base.vm' (see line 201)

drivers/gpu/drm/nouveau/nouveau_bo.c
   200		int type = ttm_bo_type_device;
   201		int max_size = INT_MAX & ~((1 << drm->client.base.vm->vmm->lpg_shift) - 1);
                                                 ^^^^^^^^^^^^^^^^^^^
New dereference.

   202	
   203		if (size <= 0 || size > max_size) {
   204			nv_warn(drm, "skipped size %x\n", (u32)size);
   205			return -EINVAL;
   206		}
   207	
   208		if (sg)
   209			type = ttm_bo_type_sg;
   210	
   211		nvbo = kzalloc(sizeof(struct nouveau_bo), GFP_KERNEL);
   212		if (!nvbo)
   213			return -ENOMEM;
   214		INIT_LIST_HEAD(&nvbo->head);
   215		INIT_LIST_HEAD(&nvbo->entry);
   216		INIT_LIST_HEAD(&nvbo->vma_list);
   217		nvbo->tile_mode = tile_mode;
   218		nvbo->tile_flags = tile_flags;
   219		nvbo->bo.bdev = &drm->ttm.bdev;
   220	
   221		nvbo->page_shift = 12;
   222		if (drm->client.base.vm) {
                    ^^^^^^^^^^^^^^^^^^^
Old check.

   223			if (!(flags & TTM_PL_FLAG_TT) && size > 256 * 1024)
   224				nvbo->page_shift = drm->client.base.vm->vmm->lpg_shift;

regards,
dan carpenter