Redis A tiny problem with sds allocation logic, possibly leading to a crash

NULL test of sh after s_malloc should be first conducted before memset(sh), possible crash if sh in memset is NULL. ---------change the original code below ---------

sds sdsnewlen(const void *init, size_t initlen) {
    ...
    sh = s_malloc(hdrlen+initlen+1);
    if (init==SDS_NOINIT)
        init = NULL;
    else if (!init)
        memset(sh, 0, hdrlen+initlen+1);
    if (sh == NULL) return NULL;
    ...
}

--------to this one ------------------

sds sdsnewlen(const void *init, size_t initlen) {
    ...
    sh = s_malloc(hdrlen+initlen+1);
    if (sh == NULL) return NULL;     // NULL test right after s_malloc
    if (init==SDS_NOINIT)
        init = NULL;
    else if (!init)
        memset(sh, 0, hdrlen+initlen+1);
    ...
}

Comment From: trevor211

dup of #6369 @soloestoy

Comment From: oranagra

@trevor211 thanks. as stated in the issue linked above, this was never a problem, but it is fixed anyway already.