diff --git a/lib/string.c b/lib/string.c
index 485777c9da83..6f334420f687 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -517,21 +517,13 @@ EXPORT_SYMBOL(strnlen);
 size_t strspn(const char *s, const char *accept)
 {
 	const char *p;
-	const char *a;
-	size_t count = 0;
 
 	for (p = s; *p != '\0'; ++p) {
-		for (a = accept; *a != '\0'; ++a) {
-			if (*p == *a)
-				break;
-		}
-		if (*a == '\0')
-			return count;
-		++count;
+		if (!strchr(accept, *p))
+			break;
 	}
-	return count;
+	return p - s;
 }
-
 EXPORT_SYMBOL(strspn);
 #endif
 
@@ -544,17 +536,12 @@ EXPORT_SYMBOL(strspn);
 size_t strcspn(const char *s, const char *reject)
 {
 	const char *p;
-	const char *r;
-	size_t count = 0;
 
 	for (p = s; *p != '\0'; ++p) {
-		for (r = reject; *r != '\0'; ++r) {
-			if (*p == *r)
-				return count;
-		}
-		++count;
+		if (strchr(reject, *p))
+			break;
 	}
-	return count;
+	return p - s;
 }
 EXPORT_SYMBOL(strcspn);
 #endif