checkpatch: warn about memset with swapped arguments

Because the second and third arguments of memset have the same type, it
turns out to be really easy to mix them up.

This bug comes up time after time, so checkpatch should really be checking
for it at patch submission time.

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

scripts/checkpatch.pl

@@ -2902,6 +2902,11 @@ sub process {
 		    $line =~ /DEVICE_ATTR.*S_IWUGO/ ) {
 			WARN("Exporting world writable files is usually an error. Consider more restrictive permissions.\n" . $herecurr);
 		}
+
+		# Check for memset with swapped arguments
+		if ($line =~ /memset.*\,(\ |)(0x|)0(\ |0|)\);/) {
+			ERROR("memset size is 3rd argument, not the second.\n" . $herecurr);
+		}
 	}
 
 	# If we have no input at all, then there is nothing to report on