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authorJon Paul Maloy <jon.maloy@ericsson.com>2016-02-24 11:10:48 -0500
committerDavid S. Miller <davem@davemloft.net>2016-02-25 17:04:48 -0500
commitd25a01257e422a4bdeb426f69529d57c73b235fe (patch)
tree09941b9ca9b6136a6f3a3cb0458cbfaf1656bad3
parentb170997acedc6c11ed2ec07b8d415601e65bb452 (diff)
tipc: fix crash during node removal
When the TIPC module is unloaded, we have identified a race condition that allows a node reference counter to go to zero and the node instance being freed before the node timer is finished with accessing it. This leads to occasional crashes, especially in multi-namespace environments. The scenario goes as follows: CPU0:(node_stop) CPU1:(node_timeout) // ref == 2 1: if(!mod_timer()) 2: if (del_timer()) 3: tipc_node_put() // ref -> 1 4: tipc_node_put() // ref -> 0 5: kfree_rcu(node); 6: tipc_node_get(node) 7: // BOOM! We now clean up this functionality as follows: 1) We remove the node pointer from the node lookup table before we attempt deactivating the timer. This way, we reduce the risk that tipc_node_find() may obtain a valid pointer to an instance marked for deletion; a harmless but undesirable situation. 2) We use del_timer_sync() instead of del_timer() to safely deactivate the node timer without any risk that it might be reactivated by the timeout handler. There is no risk of deadlock here, since the two functions never touch the same spinlocks. 3: We remove a pointless tipc_node_get() + tipc_node_put() from the timeout handler. Reported-by: Zhijiang Hu <huzhijiang@gmail.com> Acked-by: Ying Xue <ying.xue@windriver.com> Signed-off-by: Jon Maloy <jon.maloy@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/tipc/node.c24
1 files changed, 11 insertions, 13 deletions
diff --git a/net/tipc/node.c b/net/tipc/node.c
index 792bbcbb3eed..cdb79503d890 100644
--- a/net/tipc/node.c
+++ b/net/tipc/node.c
@@ -225,9 +225,10 @@ static unsigned int tipc_hashfn(u32 addr)
static void tipc_node_kref_release(struct kref *kref)
{
- struct tipc_node *node = container_of(kref, struct tipc_node, kref);
+ struct tipc_node *n = container_of(kref, struct tipc_node, kref);
- tipc_node_delete(node);
+ kfree(n->bc_entry.link);
+ kfree_rcu(n, rcu);
}
static void tipc_node_put(struct tipc_node *node)
@@ -395,21 +396,20 @@ static void tipc_node_delete(struct tipc_node *node)
{
list_del_rcu(&node->list);
hlist_del_rcu(&node->hash);
- kfree(node->bc_entry.link);
- kfree_rcu(node, rcu);
+ tipc_node_put(node);
+
+ del_timer_sync(&node->timer);
+ tipc_node_put(node);
}
void tipc_node_stop(struct net *net)
{
- struct tipc_net *tn = net_generic(net, tipc_net_id);
+ struct tipc_net *tn = tipc_net(net);
struct tipc_node *node, *t_node;
spin_lock_bh(&tn->node_list_lock);
- list_for_each_entry_safe(node, t_node, &tn->node_list, list) {
- if (del_timer(&node->timer))
- tipc_node_put(node);
- tipc_node_put(node);
- }
+ list_for_each_entry_safe(node, t_node, &tn->node_list, list)
+ tipc_node_delete(node);
spin_unlock_bh(&tn->node_list_lock);
}
@@ -530,9 +530,7 @@ static void tipc_node_timeout(unsigned long data)
if (rc & TIPC_LINK_DOWN_EVT)
tipc_node_link_down(n, bearer_id, false);
}
- if (!mod_timer(&n->timer, jiffies + n->keepalive_intv))
- tipc_node_get(n);
- tipc_node_put(n);
+ mod_timer(&n->timer, jiffies + n->keepalive_intv);
}
/**