Commit 74b885cf authored by Florian Zumbiehl's avatar Florian Zumbiehl Committed by David S. Miller

[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 ...

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: default avatarFlorian Zumbiehl <>
Acked-by: default avatarMichal Ostrowski <>
Signed-off-by: default avatarDavid S. Miller <>
parent bfafb26e
......@@ -218,17 +218,6 @@ static inline struct pppox_sock *get_item_by_addr(struct sockaddr_pppox *sp)
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;
i = __set_item(po);
return i;
static inline struct pppox_sock *delete_item(unsigned long sid, char *addr, int ifindex)
struct pppox_sock *ret;
......@@ -595,14 +584,18 @@ static int pppoe_connect(struct socket *sock, struct sockaddr *uservaddr,
po->pppoe_dev = dev;
po->pppoe_ifindex = dev->ifindex;
if (!(dev->flags & IFF_UP))
if (!(dev->flags & IFF_UP)){
goto err_put;
sizeof(struct pppoe_addr));
error = set_item(po);
error = __set_item(po);
if (error < 0)
goto err_put;
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