Re: [PATCH] add umask parameter to procfs

[Andrew Morton <akpm@osdl.org>]

Rene Scharfe <rene.scharfe@lsrfire.ath.cx> wrote:
>
> Add proc.umask kernel parameter.  It can be used to restrict permissions
> on the numerical directories in the root of a proc filesystem, i.e. the
> directories containing process specific information.
> 
> E.g. add proc.umask=077 to your kernel command line and all users except
> root can only see their own process details (like command line
> parameters) with ps or top.  It can be useful to add a bit of privacy to
> multi-user servers.
> 
> The patch has been inspired by a similar feature in GrSecurity.
> 
> It could have also been implemented as a mount option to procfs, but at
> a higher cost and no apparent benefit -- changes to this umask are not
> supposed to happen very often.  Actually, the previous incarnation of
> this patch was implemented as a half-assed mount option, but I didn't
> know then how easy it is to add a kernel parameter.

The feature seems fairly obscure, although very simple.  Is anyone actually
likely to use this?

>  
> +static umode_t umask = 0;

a) I think the above should be called proc_umask.

b) You shouldn't initialise it.

c) When adding a kernel parameter you should update
   Documentation/kernel-parameters.txt