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net: tipc: remove one synchronize_net() from tipc_nametbl_stop()

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tipc_exit_net() is very slow and is abused by syzbot.

tipc_nametbl_stop() is called for each netns being dismantled.

Calling synchronize_net() right before freeing tn->nametbl
is a big hammer.

Replace this with kfree_rcu().

Note that RCU is not properly used here, otherwise
tn->nametbl should be cleared before the synchronize_net()
or kfree_rcu(), or even before the cleanup loop.

We might need to fix this at some point.

Also note tipc uses other synchronize_rcu() calls,
more work is needed to make tipc_exit_net() much faster.

List of remaining calls to synchronize_rcu()

  tipc_detach_loopback() (dev_remove_pack())
  tipc_bcast_stop()
  tipc_sk_rht_destroy()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241204210234.319484-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2024-12-04 21:02:34 +00:00 committed by Jakub Kicinski
parent e36d46b9af
commit 6c36b5c244
2 changed files with 4 additions and 2 deletions
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4
net/tipc/name_table.c
View File

@ -949,8 +949,8 @@ void tipc_nametbl_stop(struct net *net)
}
spin_unlock_bh(&tn->nametbl_lock);
synchronize_net();
kfree(nt);
/* TODO: clear tn->nametbl, implement proper RCU rules ? */
kfree_rcu(nt, rcu);
}
static int __tipc_nl_add_nametable_publ(struct tipc_nl_msg *msg,

2
net/tipc/name_table.h
View File

@ -90,6 +90,7 @@ struct publication {
/**
* struct name_table - table containing all existing port name publications
* @rcu: RCU callback head used for deferred freeing
* @services: name sequence hash lists
* @node_scope: all local publications with node scope
* - used by name_distr during re-init of name table
@ -102,6 +103,7 @@ struct publication {
* @snd_nxt: next sequence number to be used
*/
struct name_table {
struct rcu_head rcu;
struct hlist_head services[TIPC_NAMETBL_SIZE];
struct list_head node_scope;
struct list_head cluster_scope;