From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755181AbdL1RzH (ORCPT ); Thu, 28 Dec 2017 12:55:07 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59100 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754258AbdL1RNx (ORCPT ); Thu, 28 Dec 2017 12:13:53 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "David Howells" , "Dmitry Kasatkin" , "Eric Biggers" , "James Morris" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 111/204] lib/digsig: fix dereference of NULL user_key_payload In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit 192cabd6a296cbc57b3d8c05c4c89d87fc102506 upstream. digsig_verify() requests a user key, then accesses its payload. However, a revoked key has a NULL payload, and we failed to check for this. request_key() *does* skip revoked keys, but there is still a window where the key can be revoked before we acquire its semaphore. Fix it by checking for a NULL payload, treating it like a key which was already revoked at the time it was requested. Fixes: 051dbb918c7f ("crypto: digital signature verification support") Reviewed-by: James Morris Cc: Dmitry Kasatkin Signed-off-by: Eric Biggers Signed-off-by: David Howells [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- lib/digsig.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/lib/digsig.c +++ b/lib/digsig.c @@ -86,6 +86,12 @@ static int digsig_verify_rsa(struct key down_read(&key->sem); ukp = key->payload.data; + if (!ukp) { + /* key was revoked before we acquired its semaphore */ + err = -EKEYREVOKED; + goto err1; + } + if (ukp->datalen < sizeof(*pkh)) goto err1;