checkpatch: close filp_open loophole.

filp_open allows people to get around the ban on sys_open.
Close the loophole.

Change-Id: I6e2be62e848cbc064e07008d0886c0d003c8be4b
Signed-off-by: Gregory Bean <gbean@codeaurora.org>
(cherry picked from commit bb181a18a813a70176f71a0c64aa572fcfbef0f0)
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 10f3a3e..700d5e2 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5095,6 +5095,13 @@
 			      $herecurr);
 		}
 
+# filp_open is a backdoor for sys_open
+		if ($line =~ /\b(filp_open)\b/) {
+			ERROR("FILE_OPS",
+			      "$1 is inappropriate in kernel code.\n" .
+			      $herecurr);
+		}
+
 # read[bwl] & write[bwl] use too many barriers, use the _relaxed variants
 		if ($line =~ /\b((?:read|write)[bwl])\b/) {
 			ERROR("NON_RELAXED_IO",