[PPPOE]: race between interface going down and connect()
below you find a patch that (hopefully) fixes a race between an interface
going down and a connect() to a peer on that interface. Before,
connect() would determine that an interface is up, then the interface
could go down and all entries referring to that interface in the
item_hash_table would be marked as ZOMBIEs and their references to
the device would be freed, and after that, connect() would put a new
entry into the hash table referring to the device that meanwhile is
down already - which also would cause unregister_netdevice() to wait
until the socket has been release()d.
This patch does not suffice if we are not allowed to accept connect()s
referring to a device that we already acked a NETDEV_GOING_DOWN for
(that is: all references are only guaranteed to be freed after
NETDEV_DOWN has been acknowledged, not necessarily after the
NETDEV_GOING_DOWN already). And if we are allowed to, we could avoid
looking through the hash table upon NETDEV_GOING_DOWN completely and
only do that once we get the NETDEV_DOWN ...
mostrows:
pppoe_flush_dev is called on NETDEV_GOING_DOWN and NETDEV_DOWN to deal with
this "late connect" issue. Ideally one would hope to notify users at the
"NETDEV_GOING_DOWN" phase (just to pretend to be nice). However, it is the
NETDEV_DOWN scan that takes all the responsibility for ensuring nobody is
hanging around at that time.
Signed-off-by: Florian Zumbiehl <florz@florz.de>
Acked-by: Michal Ostrowski <mostrows@earthlink.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/pppoe.c b/drivers/net/pppoe.c
index f761a9a..bc4fc30 100644
--- a/drivers/net/pppoe.c
+++ b/drivers/net/pppoe.c
@@ -218,17 +218,6 @@
return get_item(sp->sa_addr.pppoe.sid, sp->sa_addr.pppoe.remote, ifindex);
}
-static inline int set_item(struct pppox_sock *po)
-{
- int i;
-
- write_lock_bh(&pppoe_hash_lock);
- i = __set_item(po);
- write_unlock_bh(&pppoe_hash_lock);
-
- return i;
-}
-
static inline struct pppox_sock *delete_item(unsigned long sid, char *addr, int ifindex)
{
struct pppox_sock *ret;
@@ -595,14 +584,18 @@
po->pppoe_dev = dev;
po->pppoe_ifindex = dev->ifindex;
- if (!(dev->flags & IFF_UP))
+ write_lock_bh(&pppoe_hash_lock);
+ if (!(dev->flags & IFF_UP)){
+ write_unlock_bh(&pppoe_hash_lock);
goto err_put;
+ }
memcpy(&po->pppoe_pa,
&sp->sa_addr.pppoe,
sizeof(struct pppoe_addr));
- error = set_item(po);
+ error = __set_item(po);
+ write_unlock_bh(&pppoe_hash_lock);
if (error < 0)
goto err_put;