[Drbd-dev] [CASE-38] self uuid may be crashed beacuse of garbage bitmap_index value.

[Roland Kammerer]

On Wed, Mar 30, 2016 at 06:18:50PM +0900, Jaeheon Kim wrote:
> Hi,
> 
> There is some suspicious code.
> Please check following code in drbd_uuid_compare.
> 
>  --- code snip start ---
> *rule_nr = 70;
> self = drbd_bitmap_uuid(peer_device) & ~UUID_PRIMARY;
> peer = peer_device->current_uuid & ~UUID_PRIMARY;
> if (self == peer)
> return 2;
> 
> *rule_nr = 72;
> for (i = 0; i < DRBD_NODE_ID_MAX; i++) {
>     if (i == peer_device->node_id)
>           continue;
>     if (i == device->ldev->md.node_id)
>           continue;
> 
> #ifdef
> _WIN32_V9_INSERT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> /* Skip bitmap indexes which are not assigned to a peer. */
>       if (device->ldev->md.peers[i].bitmap_index == -1)
>            continue;
> #endif //
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
> 
>      self = device->ldev->md.peers[i].bitmap_uuid & ~UUID_PRIMARY;
>      if (self == peer) {
>           *peer_node_id = i;
>            return 4;
>       }
> }
> ------ code done --------
> 
> If you don't skip undefnded bitmap_index, self uuid will get crashed data.
> So, we insert this skip logic.
> What do you think about it?

on a first look this seems reasonable, but I have to further think about
it and discuss it with my colleagues.

Would be great if you could provide the steps how to trigger that
specific scenario.

Regards, rck