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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 A2894C3A5A6 for ; Thu, 19 Sep 2019 22:14:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74974218AF for ; Thu, 19 Sep 2019 22:14:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931297; bh=dHaNzdX8RhfYNR3G9kvpasvBZPNiOdCFP+q6x9pJ5Pw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=r9XlRh9pMEZ8gaIeyRlexB34N6mLchYAlVBjgyt5BQ3Hv6JHtcSpQMp5X06EsNniY gKCgLFq78+aIb4zpCTknHA2idrAZfDlGY1rpQUEjm7RZ8a13LE/xQpvQsKo8EcUAAp Z0+5huBal9HEqJ2jmBnCAjT0hPxjZT7ZwkcRym0Y= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393832AbfISWOz (ORCPT ); Thu, 19 Sep 2019 18:14:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:54542 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391738AbfISWOv (ORCPT ); Thu, 19 Sep 2019 18:14:51 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 58CB8218AF; Thu, 19 Sep 2019 22:14:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931290; bh=dHaNzdX8RhfYNR3G9kvpasvBZPNiOdCFP+q6x9pJ5Pw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tINvof8JTFdu5wujpvh+q7qAnDISkgRA93YDK3WcPVz7PTz367JUfgmH1XVdCLXiY aTZ5ruQ/l/+iJtnOFVAyqLya8BYajnXS4zS1Mkc26ub7favhDjDD9aceEwzHgNEnb4 dkswo1KULbf3Qt2UA1es1QW6BTrR6Ddi2QZZ8pCo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sachin Sant , Hillf Danton , David Howells , Linus Torvalds , Sasha Levin Subject: [PATCH 4.19 71/79] keys: Fix missing null pointer check in request_key_auth_describe() Date: Fri, 20 Sep 2019 00:03:56 +0200 Message-Id: <20190919214813.999536299@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190919214807.612593061@linuxfoundation.org> References: <20190919214807.612593061@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hillf Danton [ Upstream commit d41a3effbb53b1bcea41e328d16a4d046a508381 ] 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: Sasha Levin --- security/keys/request_key_auth.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index 5e515791ccd11..1d34b2a5f485e 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -71,6 +71,9 @@ static void request_key_auth_describe(const struct key *key, { struct request_key_auth *rka = get_request_key_auth(key); + if (!rka) + return; + seq_puts(m, "key:"); seq_puts(m, key->description); if (key_is_positive(key)) @@ -88,6 +91,9 @@ static long request_key_auth_read(const struct key *key, size_t datalen; long ret; + if (!rka) + return -EKEYREVOKED; + datalen = rka->callout_len; ret = datalen; -- 2.20.1