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| /openbmc/linux/net/core/ |
| H A D | net_namespace.c | diff 0c06bea919f3289368a023d1a62a1bc319617fa3 Tue Jan 16 03:31:41 CST 2018 Kirill Tkhai <ktkhai@virtuozzo.com> net: Fix possible race in peernet2id_alloc()
peernet2id_alloc() is racy without rtnl_lock() as refcount_read(&peer->count)
under net->nsid_lock does not guarantee, peer is alive:
rcu_read_lock()
peernet2id_alloc() ..
spin_lock_bh(&net->nsid_lock) ..
refcount_read(&peer->count) (!= 0) ..
.. put_net()
.. cleanup_net()
.. for_each_net(tmp)
.. spin_lock_bh(&tmp->nsid_lock)
.. __peernet2id(tmp, net) == -1
.. ..
.. ..
__peernet2id_alloc(alloc == true) ..
.. ..
rcu_read_unlock() ..
.. synchronize_rcu()
.. kmem_cache_free(net)
After the above situation, net::netns_id contains id pointing to freed memory,
and any other dereferencing by the id will operate with this freed memory.
Currently, peernet2id_alloc() is used under rtnl_lock() everywhere except
ovs_vport_cmd_fill_info(), and this race can't occur. But peernet2id_alloc()
is generic interface, and better we fix it before someone really starts
use it in wrong context.
v2: Don't place refcount_read(&net->count) under net->nsid_lock
as suggested by Eric W. Biederman <ebiederm@xmission.com>
v3: Rebase on top of net-next
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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