lib32-glibc: denial of service

clntudp_call allocates a buffer, using alloca, to store the payload of
an incoming socket error. If a malicious server floods the client with
crafted ICMP and UDP packets, this can cause the client to allocate
sufficiently many such temporary buffers to cause a stack (frame)
overflow (denial of service).

The size of the allocated buffer depends on the request size. If the
request size is close to the page size or even larger, this could cause
the stack pointer to step over the guard page, leading to additional
impact beyond denial of service.