Re: [PATCH v4 11/14] drm/panfrost: Add a PANFROST_SYNC_BO ioctl

["Marcin Ślusarz" <marcin.slusarz@arm.com>]

On Wed, Oct 15, 2025 at 06:03:23PM +0200, Boris Brezillon wrote:
> +static int panfrost_ioctl_sync_bo(struct drm_device *ddev, void *data,
> +				  struct drm_file *file)
> +{
> +	struct drm_panfrost_sync_bo *args = data;
> +	struct drm_panfrost_bo_sync_op *ops;
> +	struct drm_gem_object *obj;
> +	int ret;
> +	u32 i;
> +
> +	if (args->pad)
> +		return -EINVAL;
> +
> +	ops = kvmalloc_array(args->op_count, sizeof(*ops), GFP_KERNEL);
> +	if (!ops) {
> +		DRM_DEBUG("Failed to allocate incoming BO sync ops array\n");
> +		return -ENOMEM;
> +	}
> +
> +	if (copy_from_user(ops, (void __user *)(uintptr_t)args->ops,
> +			   args->op_count * sizeof(*ops))) {
> +		DRM_DEBUG("Failed to copy in BO sync ops\n");
> +		ret = -EFAULT;
> +		goto err_ops;
> +	}
> +
> +	for (i = 0; i < args->op_count; i++) {

If args->op_count is 0, if I'm not mistaken, kvmalloc_array and
copy_to_user will succeed, but then this function will return
unitialized value. Maybe add an explicit check for op_count == 0
at the beginning and avoid going through all that code?

> +		if (ops[i].flags & ~PANFROST_BO_SYNC_OP_FLAGS) {
> +			ret = -EINVAL;
> +			goto err_ops;
> +		}
> +
> +		obj = drm_gem_object_lookup(file, ops[i].handle);
> +		if (!obj) {
> +			ret = -ENOENT;
> +			goto err_ops;
> +		}
> +
> +		ret = panfrost_gem_sync(obj, ops[i].flags,
> +					ops[i].offset, ops[i].size);
> +
> +		drm_gem_object_put(obj);
> +
> +		if (ret)
> +			goto err_ops;
> +	}
> +
> +err_ops:
> +	kvfree(ops);
> +
> +	return ret;
> +}