sunrpc: Avoid use-after-free read access in clntudp_call [BZ #21115]
After commit
bc779a1a5b3035133024b21e2f339fe4219fb11c
(CVE-2016-4429: sunrpc: Do not use alloca in clntudp_call
[BZ #20112]), ancillary data is stored on the heap,
but it is accessed after it has been freed.
The test case must be run under a heap debugger such as valgrind
to observe the invalid access. A malloc implementation which
immediately calls munmap on free would catch this bug as well.
(cherry picked from commit
d42eed4a044e5e10dfb885cf9891c2518a72a491)
(cherry picked from commit
045e368799cd253ddbf8bdec42ed92e8ebb3ce67)