diff --git a/arch/x86/lib/cmdline.c b/arch/x86/lib/cmdline.c
index 422db000d727..49548bed2301 100644
--- a/arch/x86/lib/cmdline.c
+++ b/arch/x86/lib/cmdline.c
@@ -21,12 +21,14 @@ static inline int myisspace(u8 c)
  * @option: option string to look for
  *
  * Returns the position of that @option (starts counting with 1)
- * or 0 on not found.
+ * or 0 on not found.  @option will only be found if it is found
+ * as an entire word in @cmdline.  For instance, if @option="car"
+ * then a cmdline which contains "cart" will not match.
  */
 int cmdline_find_option_bool(const char *cmdline, const char *option)
 {
 	char c;
-	int len, pos = 0, wstart = 0;
+	int pos = 0, wstart = 0;
 	const char *opptr = NULL;
 	enum {
 		st_wordstart = 0,	/* Start of word/after whitespace */
@@ -37,11 +39,14 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 	if (!cmdline)
 		return -1;      /* No command line */
 
-	len = min_t(int, strlen(cmdline), COMMAND_LINE_SIZE);
-	if (!len)
+	if (!strlen(cmdline))
 		return 0;
 
-	while (len--) {
+	/*
+	 * This 'pos' check ensures we do not overrun
+	 * a non-NULL-terminated 'cmdline'
+	 */
+	while (pos < COMMAND_LINE_SIZE) {
 		c = *(char *)cmdline++;
 		pos++;
 
@@ -58,17 +63,26 @@ int cmdline_find_option_bool(const char *cmdline, const char *option)
 			/* fall through */
 
 		case st_wordcmp:
-			if (!*opptr)
+			if (!*opptr) {
+				/*
+				 * We matched all the way to the end of the
+				 * option we were looking for.  If the
+				 * command-line has a space _or_ ends, then
+				 * we matched!
+				 */
 				if (!c || myisspace(c))
 					return wstart;
 				else
 					state = st_wordskip;
-			else if (!c)
+			} else if (!c) {
+				/*
+				 * Hit the NULL terminator on the end of
+				 * cmdline.
+				 */
 				return 0;
-			else if (c != *opptr++)
+			} else if (c != *opptr++) {
 				state = st_wordskip;
-			else if (!len)		/* last word and is matching */
-				return wstart;
+			}
 			break;
 
 		case st_wordskip: