[asterisk-dev] list operations in masquerade

[Stanisław Pitucha]

Hi all,
I've found a problem which affects local old asterisk (1.4.11), but it
seems it hasn't been fixed in trunk. I'm not even sure it will crash
the new versions. Anyways:

In ast_do_masquerade(), if the clonechan->readq is empty, it crashed
our installation.
AST_LIST_APPEND_LIST(&original->readq, &clonechan->readq, frame_list);
This macro does not check if the source list is empty, so after it
appends, original->readq->first is not NULL, but ...->last is NULL. It
causes a crash later on, as original->readq becomes broken. We fixed
it by updating the macro to:

#define AST_LIST_APPEND_LIST(head, list, field) do {    \
     if ((list)->first) {    \
               if (!(head)->first) {               \
                        (head)->first = (list)->first;   \
                        (head)->last = (list)->last;   \
               } else {                           \
                        (head)->last->field.next = (list)->first;  \
                        (head)->last = (list)->last;    \
               }       \
      }        \
      (list)->first = NULL; \
      (list)->last = NULL; \
} while (0)

I'm not sure if that situation is possible in trunk anymore. If
someone could confirm it's still broken, I'll just open a bug with
this patch.

-- 
Kind regards,

Stanisław Pitucha, Gradwell Voip Engineer

T: 01225 800 851 | F: 01225 800 801 | E: stanis at gradwell.net | www.gradwell.com

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