inetpeer: fix a race in inetpeer_gc_worker()

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>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index b94765e38e80..2040bff945d4 100644
--- 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