mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 05:48:40 +00:00
![]() The comment about "race free view of the set of network namespaces" was a bit hasty. Look (there even can be only one CPU, as discovered by Alexey Dobriyan and Denis Lunev): put_net() if (atomic_dec_and_test(&net->refcnt)) /* true */ __put_net(net); queue_work(...); /* * note: the net now has refcnt 0, but still in * the global list of net namespaces */ == re-schedule == register_pernet_subsys(&some_ops); register_pernet_operations(&some_ops); (*some_ops)->init(net); /* * we call netlink_kernel_create() here * in some places */ netlink_kernel_create(); sk_alloc(); get_net(net); /* refcnt = 1 */ /* * now we drop the net refcount not to * block the net namespace exit in the * future (or this can be done on the * error path) */ put_net(sk->sk_net); if (atomic_dec_and_test(&...)) /* * true. BOOOM! The net is * scheduled for release twice */ When thinking on this problem, I decided, that getting and putting the net in init callback is wrong. If some init callback needs to have a refcount-less reference on the struct net, _it_ has to be careful himself, rather than relying on the infrastructure to handle this correctly. In case of netlink_kernel_create(), the problem is that the sk_alloc() gets the given namespace, but passing the info that we don't want to get it inside this call is too heavy. Instead, I propose to crate the socket inside an init_net namespace and then re-attach it to the desired one right after the socket is created. After doing this, we also have to be careful on error paths not to drop the reference on the namespace, we didn't get the one on. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Acked-by: Denis Lunev <den@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net> |
||
---|---|---|
.. | ||
af_netlink.c | ||
attr.c | ||
genetlink.c | ||
Makefile |