drm/tegra: Check syncpoint ID in the 'submit' IOCTL

In case of invalid syncpoint ID, the host1x_syncpt_get() returns NULL and
none of its users perform a check of the returned pointer later. Let's bail
out until it's too late.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/drm.c

@@ -393,6 +393,8 @@ int tegra_drm_submit(struct tegra_drm_context *context,
 	struct drm_tegra_waitchk __user *waitchks =
 		(void __user *)(uintptr_t)args->waitchks;
 	struct drm_tegra_syncpt syncpt;
+	struct host1x *host1x = dev_get_drvdata(drm->dev->parent);
+	struct host1x_syncpt *sp;
 	struct host1x_job *job;
 	int err;
 
@@ -522,6 +524,13 @@ int tegra_drm_submit(struct tegra_drm_context *context,
 		goto fail;
 	}
 
+	/* check whether syncpoint ID is valid */
+	sp = host1x_syncpt_get(host1x, syncpt.id);
+	if (!sp) {
+		err = -ENOENT;
+		goto fail;
+	}
+
 	job->is_addr_reg = context->client->ops->is_addr_reg;
 	job->syncpt_incrs = syncpt.incrs;
 	job->syncpt_id = syncpt.id;