Re: + procfs-expose-umask-in-proc-pid-status.patch added to -mm tree

["Richard W.M. Jones" <rjones@redhat.com>]

On Mon, Apr 25, 2016 at 11:31:55AM +0200, Michal Hocko wrote:
> On Fri 22-04-16 13:54:36, Andrew Morton wrote:
> > From: "Richard W.M. Jones" <rjones@redhat.com>
> > Subject: procfs: expose umask in /proc/<PID>/status
> > 
> > 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.
> > 
> > This patch is adapted from one originally written by Pierre Carrier.
> > 
> > 
> > The use case is that we have endless trouble with people setting weird
> > umask() values (usually on the grounds of "security"), and then everything
> > breaking.  I'm on the hook to fix these.  We'd like to add debugging to
> > our program so we can dump out the umask in debug reports.
> > 
> > Previous versions of the patch used a syscall so you could only read your
> > own umask.  That's all I need.  However there was quite a lot of push-back
> > from those, so this new version exports it in /proc.
> > 
> > See:
> > 
> 
> lkmlo.org links tend to be rather unstable from my experience. Please
> try to use lkml.kernel.org/[rg]/$msg_id as much as possible
> 
> > https://lkml.org/lkml/2016/4/13/704 [umask2]
> 
> http://lkml.kernel.org/r/1460574336-18930-1-git-send-email-rjones@redhat.com
> 
> > https://lkml.org/lkml/2016/4/13/487 [getumask]
> 
> http://lkml.kernel.org/r/1460547786-16766-1-git-send-email-rjones@redhat.com

FWIW this was heavily edited from my original commit message.  My
original commit message (minus the Signed-off-by etc) was:

    procfs: expose umask in /proc/<PID>/status
    
    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.
    
    This patch is adapted from one originally written by Pierre Carrier.

Rich.

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