Nikita Vetoshkin created ZOOKEEPER-1906:
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Summary: zkpython: invalid data in GetData for empty node
Key: ZOOKEEPER-1906
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1906
Project: ZooKeeper
Issue Type: Bug
Components: contrib-bindings
Environment: FreeBSD
Reporter: Nikita Vetoshkin
In python if we ask {{zookeeper.get}} (which translates into {{pyzoo_get}}) for
empty node we can get trash in result on Python level. Issue is pretty tricky.
It goes like this:
* python C extension allocates buffer with malloc (({{buffer =
malloc(sizeof(char)*buffer_len);}} and calls {{zoo_wget}} providing both
{{buffer}} and {{buffer_len}}.
* deserialize_GetDataResponse deserializes empty buffer and sets
{{buffer_len}} to -1 and {{zoo_wget}} returns.
* python C extension calls {{Py_BuildValue( "(s#,N)", buffer,buffer_len ...}}
with {{buffer_len}} set to -1.
* {{Py_BuildValue}} calls {{do_mkvalue}} to build python string which falls
back to {{strlen(str)}} in case string length ({{buffer_len < 0}}) - that's our
case.
* *usually* strlen returns 0, because e.g. linux uses magic zero filled page
as result of mmap (which is being copied upon page fault, i.e. when you want to
right to it)
* everything works!
But on FreeBSD (not always) we can get random data in {{malloc}} result and
this trash will be exposed to the user.
Not sure about the right way to fix this, but something like
{noformat}
Index: src/contrib/zkpython/src/c/zookeeper.c
===================================================================
--- src/contrib/zkpython/src/c/zookeeper.c (revision 1583238)
+++ src/contrib/zkpython/src/c/zookeeper.c (working copy)
@@ -1223,7 +1223,7 @@
}
PyObject *stat_dict = build_stat( &stat );
- PyObject *ret = Py_BuildValue( "(s#,N)", buffer,buffer_len, stat_dict );
+ PyObject *ret = Py_BuildValue( "(s#,N)", buffer,buffer_len < 0 ? 0 :
buffer_len, stat_dict );
free(buffer);
return ret;
{noformat}
should do the trick
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