Re: [PATCH 1/3] leaking_addresses: skip all /proc/PID except /proc/1

[Tycho Andersen]

On Fri, Mar 02, 2018 at 08:06:23AM +1100, Tobin C. Harding wrote:
> On Tue, Feb 27, 2018 at 03:45:09PM +1100, Tobin C. Harding wrote:
> > When the system is idle it is likely that most files under /proc/PID
> > will be identical for various processes.  Scanning _all_ the PIDs under
> > /proc is unnecessary and implies that we are thoroughly scanning /proc.
> > This is _not_ the case because there may be ways userspace can trigger
> > creation of /proc files that leak addresses but were not present during
> > a scan.  For these two reasons we should exclude all PID directories
> > under /proc except '1/'
> > 
> > Exclude all /proc/PID except /proc/1.
> > 
> > Signed-off-by: Tobin C. Harding <me@xxxxxxxx>
> > ---
> >  scripts/leaking_addresses.pl | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/scripts/leaking_addresses.pl b/scripts/leaking_addresses.pl
> > index 6e5bc57caeaa..fb40e2828f43 100755
> > --- a/scripts/leaking_addresses.pl
> > +++ b/scripts/leaking_addresses.pl
> > @@ -10,6 +10,14 @@
> >  # Use --debug to output path before parsing, this is useful to find files that
> >  # cause the script to choke.
> >  
> > +#
> > +# When the system is idle it is likely that most files under /proc/PID will be
> > +# identical for various processes.  Scanning _all_ the PIDs under /proc is
> > +# unnecessary and implies that we are thoroughly scanning /proc.  This is _not_
> > +# the case because there may be ways userspace can trigger creation of /proc
> > +# files that leak addresses but were not present during a scan.  For these two
> > +# reasons we exclude all PID directories under /proc except '1/'
> > +
> >  use warnings;
> >  use strict;
> >  use POSIX;
> > @@ -472,6 +480,9 @@ sub walk
> >  			my $path = "$pwd/$file";
> >  			next if (-l $path);
> >  
> > +			# skip /proc/PID except /proc/1
> > +			next if ($path =~ /\/proc\/(?:[2-9][0-9]*|1[0-9]+)/);
> 
> Perhaps the intent of this is clearer?
> 
> 			next if (($path =~ /^\/proc\/[0-9]+$/) &&
> 			     	 ($path !~ /^\/proc\/1$/));

+1, works for me.

Cheers,

Tycho