core: fix regression of false positives for processes running in chro…

…ot or mountns (#317)

needrestart

@@ -530,15 +530,21 @@ if(defined($opt_l)) {
 	# orphaned binary
 	$restart++ if (defined($exe) && $exe =~ s/ \(deleted\)$//);  # Linux
 	$restart++ if (defined($exe) && $exe =~ s/^\(deleted\)//);   # Linux VServer
-	$restart++ unless(defined($ptable->{$pid}->{exec}));
 	print STDERR "$LOGPREF #$pid uses obsolete binary $exe\n" if($restart && $nrconf{verbosity} > 1);
 
 	# ignore blacklisted binaries
 	next if(grep { $exe =~ /$_/; } @{$nrconf{blacklist}});
 
-	# Sync $exe with the initial value from Proc:ProcessTable to prevent race
+	# Sync $exe with the initial value from Proc::ProcessTable to prevent race
 	# conditions in later checks.
-	$exe = $ptable->{$pid}->{exec} if(defined($ptable->{$pid}->{exec}));
+	if(defined($ptable->{$pid}->{exec})) {
+	    $exe = $ptable->{$pid}->{exec};
+	}
+	# Proc::ProcessTable's exec field is undef if the file is not accessible in
+	# the root mountns, so the value of $exe is used instead.
+	else {
+	    $ptable->{$pid}->{exec} = $exe;
+	}
 
 	# read file mappings (Linux 2.0+)
 	unless($restart) {