From: Florian Zumbiehl Date: Fri, 20 Apr 2007 23:57:27 +0000 (-0700) Subject: [PPPOE]: race between interface going down and connect() X-Git-Tag: v2.6.22-rc1~1128^2~93 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=74b885cf86def9bc836772e3c1788c00b72a35c9;p=linux-2.6 [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 Acked-by: Michal Ostrowski Signed-off-by: David S. Miller --- diff --git a/drivers/net/pppoe.c b/drivers/net/pppoe.c index f761a9aae4..bc4fc30bc8 100644 --- a/drivers/net/pppoe.c +++ b/drivers/net/pppoe.c @@ -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; - - 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 @@ static int pppoe_connect(struct socket *sock, struct sockaddr *uservaddr, 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;