evaluate: Avoid undefined behaviour in concat_subtype_id()

For the left side of a concat expression, dtype is NULL and therefore
off is 0. In that case the code expects to get a datatype of
TYPE_INVALID, but this is fragile as the output of concat_subtype_id()
is undefined for n > 32 / TYPE_BITS.

To fix this, call datatype_lookup() directly passing the expected
TYPE_INVALID as argument if off is 0.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

0 files changed, 0 insertions, 0 deletions