On Fri, Oct 18, 2019 at 09:44:18PM +0200, Toke Høiland-Jørgensen wrote:
> It seems I forgot to add handling of devmap_hash type maps to the device
> unregister hook for devmaps. This omission causes devices to not be
> properly released, which causes hangs.
>
> Fix this by adding the missing handler.
>
> Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
> Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
> v3:
> - Use u32 for loop iterator variable
> - Since we're holding the lock we can just iterate with hlist_for_each_entry_safe()
> v2:
> - Grab the update lock while walking the map and removing entries.
>
> kernel/bpf/devmap.c | 30 ++++++++++++++++++++++++++++++
> 1 file changed, 30 insertions(+)
>
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index c0a48f336997..012dbfb0f54b 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -719,6 +719,31 @@ const struct bpf_map_ops dev_map_hash_ops = {
> .map_check_btf = map_check_no_btf,
> };
>
> +static void dev_map_hash_remove_netdev(struct bpf_dtab *dtab,
> + struct net_device *netdev)
> +{
> + unsigned long flags;
> + u32 i;
> +
> + spin_lock_irqsave(&dtab->index_lock, flags);
> + for (i = 0; i < dtab->n_buckets; i++) {
> + struct bpf_dtab_netdev *dev;
> + struct hlist_head *head;
> + struct hlist_node *next;
> +
> + head = dev_map_index_hash(dtab, i);
> +
> + hlist_for_each_entry_safe(dev, next, head, index_hlist) {
> + if (netdev != dev->dev)
> + continue;
> +
> + hlist_del_rcu(&dev->index_hlist);
There is another issue...
"dtab->items--;"
> + call_rcu(&dev->rcu, __dev_map_entry_free);
> + }
> + }
> + spin_unlock_irqrestore(&dtab->index_lock, flags);
> +}
> +
> static int dev_map_notification(struct notifier_block *notifier,
> ulong event, void *ptr)
> {
> @@ -735,6 +760,11 @@ static int dev_map_notification(struct notifier_block *notifier,
> */
> rcu_read_lock();
> list_for_each_entry_rcu(dtab, &dev_map_list, list) {
> + if (dtab->map.map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
> + dev_map_hash_remove_netdev(dtab, netdev);
> + continue;
> + }
> +
> for (i = 0; i < dtab->map.max_entries; i++) {
> struct bpf_dtab_netdev *dev, *odev;
>
> --
> 2.23.0
>
