Jared Kushner, President Trump’s son-in-law and adviser, has been granted his permanent security clearance, a person briefed on the matter said on Wednesday, ending a period of uncertainty that had fueled questions about whether Mr. Kushner was in peril in the special counsel investigation.

Mr. Kushner’s F.B.I. background checks had dragged on for a year. White House officials were adamant that the lengthy process was not unusual for a government official who has a complicated financial history and many foreign contacts. But the delay became a distraction and, with the special counsel investigating some of Mr. Kushner’s meetings with Russian officials, it left open the question of whether investigators had uncovered evidence that made him a security threat.

That was not the case, the person said, adding that Mr. Kushner’s clearances were approved by career officials after the completion of the F.B.I. background check and that the president was not involved in the process.