illumos gate

If you create a net hook with a hint of HH_BEFORE or HH_AFTER, the kstat for that hook is invalid. Specifically, the hint_value kstat_named_t (hook_hintvalue in hook_hook_kstat_t) is created as KSTAT_DATA_STRING, but no extra space is allocated in the parent kstat.

This manifests itself as the kstat command dumping core if you run it when the hooks are enabled:

> $c
libc.so.1`strlen+0x30(64ddab0, 1, 8047d08, 83c71b8)
safe_strdup+0x50(64ddab0, 83c71b8, 83c71d8, 1, 83c7048, 80c8558)
save_named+0x9d(80c8558, 83c7048, 0, a)
ks_instances_read+0x28f(806e108, fef804f0, feef56d0, 8056554, 87, 0)
main+0x5a3(8047ddc, fef6e7c8, 8047e18, 8053773, 1, 8047e24)
_start+0x83(1, 8047edc, 0, 8047ee2, 8047f08, 8047f0f)

The kstat that the kstat command chokes on has an invalid pointer to the string, 0x64ddab0:

> 80c8558::print kstat_t
{
    ks_crtime = 0x4c1452ce7a07
    ks_next = 0x80c85f8
    ks_kid = 0x8d3
    ks_module = [ "inet/NIC_EVENTS" ]
    ks_resv = 0
    ks_instance = 0
    ks_name = [ "ipfilter_hook4_nicevents" ]
    ks_type = 0x1
    ks_class = [ "hook" ]
    ks_flags = 0x1
    ks_data = 0x83c7158
    ks_ndata = 0x6
    ks_data_size = 0x120
    ks_snaptime = 0x4c1630ea4eca
    ks_update = 0
    ks_private = 0
    ks_snapshot = 0
    ks_lock = 0
}
> (0x83c7158 + 0x30 * 3::print kstat_named_t
{
    name = [ "hint_value" ]
    data_type = 0x9
    value = {
        c = [ '\\\\260', '\\\\332', 'M', '\\\\006', '\\\\0', '\\\\0', '\\\\0', '\\\\0', '\\\\034', '\\\\0', '\\\\0', '\\\\0', '\\\\0', '\\\\0', '\\\\0', '\\\\0' ]
        i32 = 0x64ddab0
        ui32 = 0x64ddab0
        str = {
            addr = {
                ptr = 0x64ddab0
                __pad = [ '\\\\260', '\\\\332', 'M', '\\\\006', '\\\\0', '\\\\0', '\\\\0', '\\\\0' ]
            }
            len = 0x0
        }
        i64 = 0x64ddab0
        ui64 = 0x64ddab0
        l = 0x64ddab0
        ul = 0x64ddab0
        ll = 0x64ddab0
        ull = 0x64ddab0
        f = +3.8716881e-35
        d = +5.2255126e-316
    }
}