[Devel] Need some assistance on msg->new_uri manipulation.

[Eliot Gable]

In my module code, I have this block of code, copied mostly from
textops.c subst_uri_f:

if(msg->new_uri.s) {
	len = msg->new_uri.len;
	tmp = msg->new_uri.s;
} else {
	tmp = msg->first_line.u.request.uri.s;
	len = msg->first_line.u.request.uri.len;
}
c = tmp[len];
tmp[len] = 0;
result = subst_str(tmp, msg, se, 0); /* pkg malloc'ed result */
tmp[len] = c;
if(result) {
/*  if(msg->new_uri.s) {
        pkg_free(msg->new_uri.s);
        msg->new_uri.s = NULL;
        msg->new_uri.len = 0;
    } */
    msg->new_uri=*result;
    msg->parsed_uri_ok = 0;
    pkg_free(result);
}
subst_expr_free(se);

If I leave the pkg_free(msg->new_uri.s) commented out, things seem to
work. But in textops.c, it frees new_uri.s if it is allocated. If I free
it in my code, I get an abort() because of a double free here in
parser/msg_parser.c:

 

/*only the content*/

void free_sip_msg(struct sip_msg* msg)

{

-->>    if (msg->new_uri.s) { pkg_free(msg->new_uri.s);
msg->new_uri.len=0; msg->n     
    if (msg->dst_uri.s) { pkg_free(msg->dst_uri.s); msg->dst_uri.len=0;
msg->d     
    if (msg->path_vec.s) { pkg_free(msg->path_vec.s);
msg->path_vec.len=0; msg     
    if (msg->headers)     free_hdr_field_lst(msg->headers);

    if (msg->add_rm)      free_lump_list(msg->add_rm);

    if (msg->body_lumps)  free_lump_list(msg->body_lumps);

    if (msg->reply_lump)   free_reply_lump(msg->reply_lump);

    /* don't free anymore -- now a pointer to a static buffer */

#   ifdef DYN_BUF

    pkg_free(msg->buf);

    msg->buf = NULL;

#   endif

}

 

Why is it that msg->new_uri.s still points to the memory location that I
freed in my code when immediately after that free I am setting new_uri.s
to a new memory location?:

msg->new_uri=*result;

Is the SIP message cloned somewhere before it is passed to my module? If
so, should I be freeing new_uri.s in my module or will it get taken care
of elsewhere in the code?


Eliot Gable
Operations Engineer
CCNA, CWNA, CWSP, Network+, Security+
Broadvox, LLC
1228 Euclid Avenue
Suite 390
Cleveland, OH 44115-1800
216-373-4808