From owner-svn-src-head@FreeBSD.ORG Tue Feb 28 15:18:27 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 13D0F1065674; Tue, 28 Feb 2012 15:18:27 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id DC7498FC17; Tue, 28 Feb 2012 15:18:26 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [96.47.65.170]) by cyrus.watson.org (Postfix) with ESMTPSA id 9304246B2D; Tue, 28 Feb 2012 10:18:26 -0500 (EST) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 8C407B967; Tue, 28 Feb 2012 10:18:25 -0500 (EST) From: John Baldwin To: Julian Elischer Date: Tue, 28 Feb 2012 08:41:53 -0500 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p10; KDE/4.5.5; amd64; ; ) References: <201202261425.q1QEPm9g069102@svn.freebsd.org> <20120227092951.GB55074@deviant.kiev.zoral.com.ua> <4F4C7571.7010407@freebsd.org> In-Reply-To: <4F4C7571.7010407@freebsd.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201202280841.53552.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Tue, 28 Feb 2012 10:18:25 -0500 (EST) Cc: src-committers@freebsd.org, Pawel Jakub Dawidek , svn-src-all@freebsd.org, Mikolaj Golub , svn-src-head@freebsd.org, Konstantin Belousov Subject: Re: svn commit: r232181 - in head/sys: kern sys X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 28 Feb 2012 15:18:27 -0000 On Tuesday, February 28, 2012 1:34:25 am Julian Elischer wrote: > On 2/27/12 1:29 AM, Konstantin Belousov wrote: > > On Mon, Feb 27, 2012 at 10:49:59AM +0200, Mikolaj Golub wrote: > >> On Mon, 27 Feb 2012 09:28:11 +0100 Pawel Jakub Dawidek wrote: > >> > >> PJD> On Sun, Feb 26, 2012 at 02:25:48PM +0000, Mikolaj Golub wrote: > >> >> Author: trociny > >> >> Date: Sun Feb 26 14:25:48 2012 > >> >> New Revision: 232181 > >> >> URL: http://svn.freebsd.org/changeset/base/232181 > >> >> > >> >> Log: > >> >> Add sysctl to retrieve or set umask of another process. > >> > >> PJD> "set umask of another process"? This seems... weird. What's the purpose > >> PJD> of this change? > >> > >> When we were discussing this with Kostik and Robert, and I asked if it could > >> be useful to have the sysctl rw, Kostik described a real situation when he had > >> had to change umask of another process: umask had not been set properly on an > >> aplication start but it could not be restarted until the end of the day. > >> Kostik was able to fix it using gdb but having an easier way looked useful. > > kgdb, not gdb. > > > > It is indeed possible to write a ptrace-based utility that inject a code > > payload that would change umask. Since this is very risky but indeed possible, > > having the straighforward kernel facility is justified. > Why not have a sysctl to change a process' uid, cwd, memory limits, > etc. etc. uid and cwd would be rediculous to change. However, we recently added sysctls to allow a sysadmin to read and write the limits of other processes (and that is a very useful feature indeed since it is not unusual for a long-running process to require more resources than it was initially allocated, as is the ability to easily query the limits that a given process is subject to). > I don't think this belongs in the kernel by default. It's not exactl a > call for backout but It's teh next thing short of that. a call for "do > you REALLY think we need this particular specific case catered for?" That said, the umask bit does strike me as a bit more odd than the limits case. I would have more need of a tool to let me adjust the listen queue length of a socket than to adjust umask (I've had to do that multiple times via kgdb). -- John Baldwin