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tipc: use node list lock to protect tipc_num_links variable 

Without properly implicit or explicit read memory barrier, it's
unsafe to read an atomic variable with atomic_read() from another
thread which is different with the thread of changing the atomic
variable with atomic_inc() or atomic_dec(). So a stale tipc_num_links
may be got with atomic_read() in tipc_node_get_links(). If the
tipc_num_links variable type is converted from atomic to unsigned
integer and node list lock is used to protect it, the issue would
be avoided.

Signed-off-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ying Xue 2014-03-27 12:54:39 +08:00 committed by David S. Miller
parent 2220646a53
commit dde2026608
1 changed files with 11 additions and 10 deletions
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21
net/tipc/node.c
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@ -47,10 +47,9 @@ static void node_established_contact(struct tipc_node *n_ptr);
static struct hlist_head node_htable[NODE_HTABLE_SIZE];
LIST_HEAD(tipc_node_list);
static u32 tipc_num_nodes;
static u32 tipc_num_links;
static DEFINE_SPINLOCK(node_list_lock);
static atomic_t tipc_num_links = ATOMIC_INIT(0);
/*
* A trivial power-of-two bitmask technique is used for speed, since this
* operation is done for every incoming TIPC packet. The number of hash table
@ -241,7 +240,9 @@ int tipc_node_is_up(struct tipc_node *n_ptr)
void tipc_node_attach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
{
n_ptr->links[l_ptr->b_ptr->identity] = l_ptr;
atomic_inc(&tipc_num_links);
spin_lock_bh(&node_list_lock);
tipc_num_links++;
spin_unlock_bh(&node_list_lock);
n_ptr->link_cnt++;
}
@ -253,7 +254,9 @@ void tipc_node_detach_link(struct tipc_node *n_ptr, struct tipc_link *l_ptr)
if (l_ptr != n_ptr->links[i])
continue;
n_ptr->links[i] = NULL;
atomic_dec(&tipc_num_links);
spin_lock_bh(&node_list_lock);
tipc_num_links--;
spin_unlock_bh(&node_list_lock);
n_ptr->link_cnt--;
}
}
@ -393,18 +396,17 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
spin_lock_bh(&node_list_lock);
/* Get space for all unicast links + broadcast link */
payload_size = TLV_SPACE(sizeof(link_info)) *
(atomic_read(&tipc_num_links) + 1);
payload_size = TLV_SPACE((sizeof(link_info)) * (tipc_num_links + 1));
if (payload_size > 32768u) {
spin_unlock_bh(&node_list_lock);
return tipc_cfg_reply_error_string(TIPC_CFG_NOT_SUPPORTED
" (too many links)");
}
spin_unlock_bh(&node_list_lock);
buf = tipc_cfg_reply_alloc(payload_size);
if (!buf) {
spin_unlock_bh(&node_list_lock);
if (!buf)
return NULL;
}
/* Add TLV for broadcast link */
link_info.dest = htonl(tipc_cluster_mask(tipc_own_addr));
@ -432,6 +434,5 @@ struct sk_buff *tipc_node_get_links(const void *req_tlv_area, int req_tlv_space)
tipc_node_unlock(n_ptr);
}
rcu_read_unlock();
spin_unlock_bh(&node_list_lock);
return buf;
}