Commit dde20266 authored by Ying Xue's avatar Ying Xue Committed by David S. Miller
Browse files

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: default avatarYing Xue <ying.xue@windriver.com>
Reviewed-by: default avatarErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2220646a

net/tipc/node.c

+11 −10
Original line number Diff line number Diff line
@@ -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)");

	}

	buf = tipc_cfg_reply_alloc(payload_size);

	if (!buf) {

	spin_unlock_bh(&node_list_lock);



	buf = tipc_cfg_reply_alloc(payload_size);

	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;

}

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