checkpatch: deprecate unbounded string functions.

Unbounded string functions are overflow risks.  The 'n'
versions of those functions should be used instead.

Change-Id: Ice0fb3ebdae9aa88cc7e764ffdf68cbed857febf
Signed-off-by: Gregory Bean <gbean@codeaurora.org>
(cherry picked from commit 15e1e97d66dd6a6039c1ec2bd549a632fe361128)
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>

scripts/checkpatch.pl

@@ -4535,6 +4535,26 @@ sub process {
 			      $herecurr);
 		}
 
+# unbounded string functions are overflow risks
+		my %str_fns = (
+			"sprintf" => "snprintf",
+			"strcpy"  => "strlcpy",
+			"strncpy"  => "strlcpy",
+			"strcat"  => "strlcat",
+			"strncat"  => "strlcat",
+			"vsprintf"  => "vsnprintf",
+			"strchr" => "strnchr",
+			"strstr" => "strnstr",
+		);
+		foreach my $k (keys %str_fns) {
+			if ($line =~ /\b$k\b/) {
+				ERROR("UNBOUNDED_STRING_FNS",
+				      "Use of $k is deprecated: " .
+				      "use $str_fns{$k} instead.\n" .
+				      $herecurr);
+			}
+		}
+
 # warn about #if 0
 		if ($line =~ /^.\s*\#\s*if\s+0\b/) {
 			WARN("IF_0",