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=-6.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,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 F0077C282DE for ; Thu, 23 May 2019 19:27:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C7FAF217D9 for ; Thu, 23 May 2019 19:27:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558639632; bh=3ZhTXSwncieJow4pLP8cZK9G6BTxT9zbZnxIHYnH+bs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=xeW9In7HIjJc9w5XkaM7ycSRo3SPvjmB55E6+Nm7XImgiAzsoOkEBVpAYrFuImIwK 59QrlHgqtged29zgAisEVAQgFv0kVtNYr8Br7hJw9kF6kILHAO0AYZymdZuCCLW8Gt NO8HC4FeeNAaQUxW+OhdU3yd355E9gi+UO2ep/34= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391551AbfEWT1M (ORCPT ); Thu, 23 May 2019 15:27:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:39292 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391536AbfEWT1K (ORCPT ); Thu, 23 May 2019 15:27:10 -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 06E8D206BA; Thu, 23 May 2019 19:27:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1558639629; bh=3ZhTXSwncieJow4pLP8cZK9G6BTxT9zbZnxIHYnH+bs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2d7gNeQvZQmkUvONDfpeTf8p5gT3CeTIBs671zveMuZe14ivizAEQvliwzCrUvP76 YMAsb1TGjBQ5MwcSC5Maj4F5vXFqKtzffjddYq3FPz6IXsxoQTGYXA/hH4y52j7YD0 hFIsb7ti4jXAHDNp98j6ZcTJcLRRN9sEFeB4dOOU= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "chengjian (D)" , Paul Moore , John Johansen , James Morris , Casey Schaufler Subject: [PATCH 5.1 036/122] proc: prevent changes to overridden credentials Date: Thu, 23 May 2019 21:05:58 +0200 Message-Id: <20190523181709.625861225@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190523181705.091418060@linuxfoundation.org> References: <20190523181705.091418060@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: Paul Moore commit 35a196bef449b5824033865b963ed9a43fb8c730 upstream. Prevent userspace from changing the the /proc/PID/attr values if the task's credentials are currently overriden. This not only makes sense conceptually, it also prevents some really bizarre error cases caused when trying to commit credentials to a task with overridden credentials. Cc: Reported-by: "chengjian (D)" Signed-off-by: Paul Moore Acked-by: John Johansen Acked-by: James Morris Acked-by: Casey Schaufler Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2540,6 +2540,11 @@ static ssize_t proc_pid_attr_write(struc rcu_read_unlock(); return -EACCES; } + /* Prevent changes to overridden credentials. */ + if (current_cred() != current_real_cred()) { + rcu_read_unlock(); + return -EBUSY; + } rcu_read_unlock(); if (count > PAGE_SIZE)