linux-kernel - Re: [PATCH] procfs: expose umask in /proc/<PID>/status (formerly umask2, formerly getumask)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 14 Apr 2016 10:36:37 +0100
From:	"Richard W.M. Jones" <rjones@...hat.com>
To:	corbet@....net
Cc:	akpm@...ux-foundation.org, vbabka@...e.cz, mhocko@...e.com,
	hughd@...gle.com, koct9i@...il.com, chenhanxiao@...fujitsu.com,
	n-horiguchi@...jp.nec.com, ross.zwisler@...ux.intel.com,
	john.stultz@...aro.org, minchan@...nel.org, jmarchan@...hat.com,
	hannes@...xchg.org, nathans@...hat.com,
	andriy.shevchenko@...ux.intel.com, keescook@...omium.org,
	gorcunov@...nvz.org, joe@...ches.com, linux@...musvillemoes.dk,
	mingo@...nel.org, cmetcalf@...hip.com, iago@...ocode.com,
	luto@...nel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, gorcunov@...il.com, fw@...eb.enyo.de,
	walters@...bum.org
Subject: Re: [PATCH] procfs: expose umask in /proc/<PID>/status (formerly
 umask2, formerly getumask)

On Thu, Apr 14, 2016 at 10:34:48AM +0100, Richard W.M. Jones wrote:
> It's not possible to read the process umask without also modifying it,
> which is what umask(2) does.  A library cannot read umask safely,
> especially if the main program might be multithreaded.
> 
> Add a new status line ("Umask") in /proc/<PID>/status.  It contains
> the file mode creation mask (umask) in octal.  It is only shown for
> tasks which have task->fs.
> 
> For the library this allows me to read the umask from
> /proc/self/status.
> 
> This patch is adapted from one originally written by Pierre Carrier:
> https://lkml.org/lkml/2012/5/4/451

Sorry, I meant to add an example of what this looks like:

$ grep Umask /proc/1/status 
Umask:	  022
$ grep Umask /proc/2/status 
Umask:	  022
$ grep Umask /proc/self/status 
Umask:	  022
$ umask 002
$ grep Umask /proc/self/status 
Umask:	  02

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-top is 'top' for virtual machines.  Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://people.redhat.com/~rjones/virt-top