dns_submit_srv() crashes if 'service' is string but 'protocol' is NULL

[Michael Tokarev]

08.02.2011 03:14, Iñaki Baz Castillo wrote:
> Hi, dns_submit_srv() allows setting both service and protocol or no
> one of them. However if 'service' is a set but 'protocol' is not, then
> the following function crashes:
> 
> build_srv_dn(dnsc_t *dn, const char *name, const char *srv, const char *proto)
> {
>   unsigned p = 0, l;
>   int isabs;
>   if (srv) {
>     l = add_sname(dn + p, srv);
>     if (!l)
>       return -1;
>     p += l;
>     l = add_sname(dn + p, proto);
>     if (!l)
>       return -1;
>     p += l;
>   }
> 
> Maybe the function should check it?

Yes it should.  This is one of very few functions in the library
which were contributed by others, and apparently I didn't check
it as carefully as my own code.  The bug is obvious, thank you
for spotting it!

/mjt