libsepol: do not wrap integers when checking bound

Some invalid policies might have p->p_types.nprim = 0. When parsing
such a policy, "i > p->p_types.nprim - 1" is always false even though
reading p->type_val_to_struct[i] triggers a segmentation fault.

Make type_set_expand() return an error when parsing such a policy by
handling correctly when p->p_types.nprim is zero.

This issue has been found while fuzzing semodule_package with the
American Fuzzy Lop.

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>
1 file changed