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inetpeer: fix a race in inetpeer_gc_worker()

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commit 5faa5df1fa (inetpeer: Invalidate the inetpeer tree along with
the routing cache) added a race :

Before freeing an inetpeer, we must respect a RCU grace period, and make
sure no user will attempt to increase refcnt.

inetpeer_invalidate_tree() waits for a RCU grace period before inserting
inetpeer tree into gc_list and waking the worker. At that time, no
concurrent lookup can find a inetpeer in this tree.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2012-06-05 03:00:18 +00:00 committed by David S. Miller
parent dd03cff23d
commit 55432d2b54
2 changed files with 16 additions and 5 deletions
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5
include/net/inetpeer.h
View File

@ -40,7 +40,10 @@ struct inet_peer {
u32 pmtu_orig;
u32 pmtu_learned;
struct inetpeer_addr_base redirect_learned;
struct list_head gc_list;
union {
struct list_head gc_list;
struct rcu_head gc_rcu;
};
/*
* Once inet_peer is queued for deletion (refcnt == -1), following fields
* are not available: rid, ip_id_count, tcp_ts, tcp_ts_stamp

16
net/ipv4/inetpeer.c
View File

@ -560,6 +560,17 @@ bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
}
EXPORT_SYMBOL(inet_peer_xrlim_allow);
static void inetpeer_inval_rcu(struct rcu_head *head)
{
struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);
spin_lock_bh(&gc_lock);
list_add_tail(&p->gc_list, &gc_list);
spin_unlock_bh(&gc_lock);
schedule_delayed_work(&gc_work, gc_delay);
}
void inetpeer_invalidate_tree(int family)
{
struct inet_peer *old, *new, *prev;
@ -576,10 +587,7 @@ void inetpeer_invalidate_tree(int family)
prev = cmpxchg(&base->root, old, new);
if (prev == old) {
base->total = 0;
spin_lock(&gc_lock);
list_add_tail(&prev->gc_list, &gc_list);
spin_unlock(&gc_lock);
schedule_delayed_work(&gc_work, gc_delay);
call_rcu(&prev->gc_rcu, inetpeer_inval_rcu);
}
out: