diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index 189badbeddaf7bf39ffd97544232aa8ba7a2f9d4..3362d866793b320149bcb7a83b663e1bb68cf927 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -594,7 +594,7 @@ static int log_mark(struct log_writes_c *lc, char *data)
 		return -ENOMEM;
 	}
 
-	block->data = kstrndup(data, maxsize, GFP_KERNEL);
+	block->data = kstrndup(data, maxsize - 1, GFP_KERNEL);
 	if (!block->data) {
 		DMERR("Error copying mark data");
 		kfree(block);