checkpatch: check for world-writeable sysfs/debugfs files

Exporting world writable sysfs/debugfs files is usually a bad thing.  Warn
about it.

Signed-off-by: Dave Jones <davej@redhat.com>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2897,6 +2897,11 @@ sub process {
 				ERROR("lockdep_no_validate class is reserved for device->mutex.\n" . $herecurr);
 			}
 		}
+
+		if ($line =~ /debugfs_create_file.*S_IWUGO/ ||
+		    $line =~ /DEVICE_ATTR.*S_IWUGO/ ) {
+			WARN("Exporting world writable files is usually an error. Consider more restrictive permissions.\n" . $herecurr);
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on