From 44524fcdf6ca19b58c24f7622c4af1d8d8fe59f8 Mon Sep 17 00:00:00 2001 From: Marek Lindner Date: Thu, 10 Feb 2011 14:33:53 +0000 Subject: batman-adv: Correct rcu refcounting for neigh_node It might be possible that 2 threads access the same data in the same rcu grace period. The first thread calls call_rcu() to decrement the refcount and free the data while the second thread increases the refcount to use the data. To avoid this race condition all refcount operations have to be atomic. Reported-by: Sven Eckelmann Signed-off-by: Marek Lindner --- net/batman-adv/icmp_socket.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-) (limited to 'net/batman-adv/icmp_socket.c') diff --git a/net/batman-adv/icmp_socket.c b/net/batman-adv/icmp_socket.c index 8e0cd8a1bc02..7fa5bb8a9409 100644 --- a/net/batman-adv/icmp_socket.c +++ b/net/batman-adv/icmp_socket.c @@ -156,7 +156,8 @@ static ssize_t bat_socket_write(struct file *file, const char __user *buff, struct sk_buff *skb; struct icmp_packet_rr *icmp_packet; - struct orig_node *orig_node; + struct orig_node *orig_node = NULL; + struct neigh_node *neigh_node = NULL; struct batman_if *batman_if; size_t packet_len = sizeof(struct icmp_packet); uint8_t dstaddr[ETH_ALEN]; @@ -224,17 +225,25 @@ static ssize_t bat_socket_write(struct file *file, const char __user *buff, orig_node = ((struct orig_node *)hash_find(bat_priv->orig_hash, compare_orig, choose_orig, icmp_packet->dst)); - rcu_read_unlock(); if (!orig_node) goto unlock; - if (!orig_node->router) + kref_get(&orig_node->refcount); + neigh_node = orig_node->router; + + if (!neigh_node) + goto unlock; + + if (!atomic_inc_not_zero(&neigh_node->refcount)) { + neigh_node = NULL; goto unlock; + } + + rcu_read_unlock(); batman_if = orig_node->router->if_incoming; memcpy(dstaddr, orig_node->router->addr, ETH_ALEN); - spin_unlock_bh(&bat_priv->orig_hash_lock); if (!batman_if) @@ -247,14 +256,14 @@ static ssize_t bat_socket_write(struct file *file, const char __user *buff, bat_priv->primary_if->net_dev->dev_addr, ETH_ALEN); if (packet_len == sizeof(struct icmp_packet_rr)) - memcpy(icmp_packet->rr, batman_if->net_dev->dev_addr, ETH_ALEN); - + memcpy(icmp_packet->rr, + batman_if->net_dev->dev_addr, ETH_ALEN); send_skb_packet(skb, batman_if, dstaddr); - goto out; unlock: + rcu_read_unlock(); spin_unlock_bh(&bat_priv->orig_hash_lock); dst_unreach: icmp_packet->msg_type = DESTINATION_UNREACHABLE; @@ -262,6 +271,10 @@ dst_unreach: free_skb: kfree_skb(skb); out: + if (neigh_node) + neigh_node_free_ref(neigh_node); + if (orig_node) + kref_put(&orig_node->refcount, orig_node_free_ref); return len; } -- cgit v1.2.3