From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751280AbVKKWip (ORCPT ); Fri, 11 Nov 2005 17:38:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751285AbVKKWim (ORCPT ); Fri, 11 Nov 2005 17:38:42 -0500 Received: from maggie.cs.pitt.edu ([130.49.220.148]:60397 "EHLO maggie.cs.pitt.edu") by vger.kernel.org with ESMTP id S1751280AbVKKWi2 (ORCPT ); Fri, 11 Nov 2005 17:38:28 -0500 From: Claudio Scordino To: Alan Cox Subject: Re: [PATCH] getrusage sucks Date: Fri, 11 Nov 2005 23:38:19 +0100 User-Agent: KMail/1.8 Cc: "Magnus Naeslund(f)" , "Hua Zhong (hzhong)" , linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org, David Wagner References: <75D9B5F4E50C8B4BB27622BD06C2B82BCF2FD4@xmb-sjc-235.amer.cisco.com> <200511110211.05642.cloud.of.andor@gmail.com> <1131715816.3174.15.camel@localhost.localdomain> In-Reply-To: <1131715816.3174.15.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200511112338.20684.cloud.of.andor@gmail.com> X-Spam-Score: -1.665/8 BAYES_00 SA-version=3.000002 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > > > You need to wrap this with a read_lock(&tasklist_lock) to be safe, I > > > think. > > > > It will depend on the data accuracy. If the information on cpu usage is > very accurate then it becomes a way to analyse what is happening to > tasks you don't own - such as say cryptographic functions in the web > server... > > Otherwise, or with an owner check I see no real problem with the concept So, is the following patch right ? I've added both the lock and the owner check... Do you think it may be an interesting feature to be inserted in the kernel ? Many thanks, Claudio diff --git a/kernel/sys.c b/kernel/sys.c --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1746,9 +1746,25 @@ int getrusage(struct task_struct *p, int asmlinkage long sys_getrusage(int who, struct rusage __user *ru) { - if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN) - return -EINVAL; - return getrusage(current, who, ru); + if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN) { + struct task_struct* tsk; + struct rusage r; + read_lock(&tasklist_lock); + tsk = find_task_by_pid(who); + if (tsk == NULL) { + read_unlock(&tasklist_lock); + return -EINVAL; + } + if ((current->euid != tsk->euid) && + (current->euid != tsk->uid)) { + read_unlock(&tasklist_lock); + return -EINVAL; + } + k_getrusage(tsk, RUSAGE_SELF, &r); + read_unlock(&tasklist_lock); + return copy_to_user(ru, &r, sizeof(r)) ? -EFAULT : 0; + } else + return getrusage(current, who, ru); } asmlinkage long sys_umask(int mask)