[ldns-users] pyldns - memory leaks and double freeing

[Bedrich Kosata]

Hi everybody,

while trying to find a cause of a memory leak in a simple script, I 
found a nest of memory related issues in the python bindings.
The problems are all related to one common problem - who takes care of 
memory of composite objects, such as ldns_rr_lists or ldns_pkt.
For example, in the current version, ldns_pkt bindings use ldns_pkt_free 
to free a packet structure, however, when a rr_list is taken from the 
packet and returned from a function, the packet gets out of scope, is 
freed and the rr_list refers to already freed memory.
On the other hand, a rr_list only frees its own memory, not memory of 
the stored rrs. This can lead to memory leaks.
I am attaching two scripts that demonstrate these problems (it might be 
necessary to have the sources patched with the "freeing None" patch I 
sent last week).
I would be willing to have a stab at the problems (provided I get 
clearance from my boss :)), but the only solution I think would be clean 
enough, is to clone the necessary bits where needed. This might lead to 
some inefficiency and slowdowns (probably not big), so I would like to 
ask if this is ok.
If there is anyone else willing to fix this, I would be happy to act as 
a tester.

Cheers

Beda

p.s.- test-pkt-free.py crashes with a segmentation fault, 
test-rr-list.py ends up eating about 130 MB of memory and more than 
400000 python objects which python cannot free.

-- 
Bedrich Kosata
CZ.NIC Labs <http://labs.nic.cz>
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