src/core/ngx_string.c:618: error: Integer Overflow L2
  ([0, `len`] - 1):unsigned64.

src/core/ngx_string.c:606:1: <LHS trace>
604. 
605. 
606. u_char *
     ^
607. ngx_strnstr(u_char *s1, char *s2, size_t len)
608. {

src/core/ngx_string.c:606:1: Parameter `len`
604. 
605. 
606. u_char *
     ^
607. ngx_strnstr(u_char *s1, char *s2, size_t len)
608. {

src/core/ngx_string.c:618:17: Binary operation: ([0, len] - 1):unsigned64
616.     do {
617.         do {
618.             if (len-- == 0) {
                     ^
619.                 return NULL;
620.             }

u_char *
ngx_strnstr(u_char *s1, char *s2, size_t len)
{
    u_char  c1, c2;
    size_t  n;
    c2 = *(u_char *) s2++;
    n = ngx_strlen(s2);
    do {
        do {
            if (len-- == 0) {
                return NULL;
            }
            c1 = *s1++;
            if (c1 == 0) {
                return NULL;
            }
        } while (c1 != c2);
        if (n > len) {
            return NULL;
        }
    } while (ngx_strncmp(s1, (u_char *) s2, n) != 0);
    return --s1;
}
['u_char *\nngx_strnstr(u_char *s1, char *s2, size_t len)\n{\n    u_char  c1, c2;\n    size_t  n;\n    c2 = *(u_char *) s2++;\n    n = ngx_strlen(s2);\n    do {\n        do {\n            if (len-- == 0) {\n                return NULL;\n            }\n            c1 = *s1++;\n            if (c1 == 0) {\n                return NULL;\n            }\n        } while (c1 != c2);\n        if (n > len) {\n            return NULL;\n        }\n    } while (ngx_strncmp(s1, (u_char *) s2, n) != 0);\n    return --s1;\n}']