description: Oxenstored 32->31 bit integer truncation issues Integers in Ocaml are 63 or 31 bits of signed precision. The Ocaml Xenbus library takes a C uint32_t out of the ring and casts it directly to an Ocaml integer. In 64-bit Ocaml builds this is fine, but in 32-bit builds, it truncates off the most significant bit, and then creates unsigned/signed confusion in the remainder. This in turn can feed a negative value into logic not expecting a negative value, resulting in unexpected exceptions being thrown. The unexpected exception is not handled suitably, creating a busy-loop trying (and failing) to take the bad packet out of the xenstore ring.
problem types: unknown
affected:
{
vendor: Xen
product: xen
versions:
version: consult Xen advisory XSA-420, status: unknown
}
metrics:
other: [
type: unknown
content: {'description': {'description_data': [{'lang': 'eng', 'value': 'A malicious or buggy guest can write a packet into the xenstore ring\nwhich causes 32-bit builds of oxenstored to busy loop.'}]}}
]