bcache: check for allocation failures

There is a missing NULL check after the kzalloc().

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index dd3f00a..12a2c28 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -232,6 +232,8 @@
 			bch_uuid_write(dc->disk.c);
 		}
 		env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL);
+		if (!env)
+			return -ENOMEM;
 		add_uevent_var(env, "DRIVER=bcache");
 		add_uevent_var(env, "CACHED_UUID=%pU", dc->sb.uuid),
 		add_uevent_var(env, "CACHED_LABEL=%s", buf);