[ 023/187] inetpeer: fix a race in inetpeer_gc_worker()

Greg Kroah-Hartman
2012-07-12T23:48:43Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 55432d2b543a4b6dfae54f5c432a566877a85d90 ]

commit 5faa5df1fa2024 (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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/net/inetpeer.h | 5 ++++-
net/ipv4/inetpeer.c | 16 ++++++++++++----
2 files changed, 16 insertions(+), 5 deletions(-)

--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -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
--- a/net/ipv4/inetpeer.c
+++ b/net/ipv4/inetpeer.c
@@ -560,6 +560,17 @@ bool inet_peer_xrlim_allow(struct inet_p
}
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);
}