From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1DB6C43215 for ; Wed, 20 Nov 2019 15:40:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C3E43218AF for ; Wed, 20 Nov 2019 15:40:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732022AbfKTPkw (ORCPT ); Wed, 20 Nov 2019 10:40:52 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:53230 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731891AbfKTPkW (ORCPT ); Wed, 20 Nov 2019 10:40:22 -0500 Received: from [167.98.27.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iXS5V-0004aq-Bg; Wed, 20 Nov 2019 15:40:13 +0000 Received: from ben by deadeye with local (Exim 4.93-RC1) (envelope-from ) id 1iXS5V-0004Ly-1l; Wed, 20 Nov 2019 15:40:13 +0000 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, Denis Kirjanov , "David Howells" , "Linus Torvalds" , "Hillf Danton" , "Sachin Sant" Date: Wed, 20 Nov 2019 15:38:17 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 67/83] keys: Fix missing null pointer check in request_key_auth_describe() In-Reply-To: X-SA-Exim-Connect-IP: 167.98.27.226 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.78-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Hillf Danton commit d41a3effbb53b1bcea41e328d16a4d046a508381 upstream. If a request_key authentication token key gets revoked, there's a window in which request_key_auth_describe() can see it with a NULL payload - but it makes no check for this and something like the following oops may occur: BUG: Kernel NULL pointer dereference at 0x00000038 Faulting instruction address: 0xc0000000004ddf30 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP [...] request_key_auth_describe+0x90/0xd0 LR [...] request_key_auth_describe+0x54/0xd0 Call Trace: [...] request_key_auth_describe+0x54/0xd0 (unreliable) [...] proc_keys_show+0x308/0x4c0 [...] seq_read+0x3d0/0x540 [...] proc_reg_read+0x90/0x110 [...] __vfs_read+0x3c/0x70 [...] vfs_read+0xb4/0x1b0 [...] ksys_read+0x7c/0x130 [...] system_call+0x5c/0x70 Fix this by checking for a NULL pointer when describing such a key. Also make the read routine check for a NULL pointer to be on the safe side. [DH: Modified to not take already-held rcu lock and modified to also check in the read routine] Fixes: 04c567d9313e ("[PATCH] Keys: Fix race between two instantiators of a key") Reported-by: Sachin Sant Signed-off-by: Hillf Danton Signed-off-by: David Howells Tested-by: Sachin Sant Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- security/keys/request_key_auth.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -58,6 +58,9 @@ static void request_key_auth_describe(co { struct request_key_auth *rka = key->payload.data; + if (!rka) + return; + seq_puts(m, "key:"); seq_puts(m, key->description); if (key_is_instantiated(key)) @@ -75,6 +78,9 @@ static long request_key_auth_read(const size_t datalen; long ret; + if (!rka) + return -EKEYREVOKED; + datalen = rka->callout_len; ret = datalen;