diff mbox series

[2/5] batman-adv: Prevent duplicated nc_node entry

Message ID 20180812190445.28013-3-sven@narfation.org
State Superseded, archived
Delegated to: Simon Wunderlich
Headers show
Series batman-adv: Missing list checks for *list_add* | expand

Commit Message

Sven Eckelmann Aug. 12, 2018, 7:04 p.m. UTC
The function batadv_nc_get_nc_node is responsible for adding new nc_nodes
to the in_coding_list and out_coding_list. It first checks whether the
entry already is in the list or not. If it is, then the creation of a new
entry is aborted.

But the lock for the list is only held when the list is really modified.
This could lead to duplicated entries because another context could create
an entry with the same key between the check and the list manipulation.

The check and the manipulation of the list must therefore be in the same
locked code section.

Fixes: 3ed7ada3f0bb ("batman-adv: network coding - detect coding nodes and remove these after timeout")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 net/batman-adv/network-coding.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

Comments

Marek Lindner Sept. 6, 2018, 11:45 a.m. UTC | #1
On Monday, 13 August 2018 03:04:42 HKT Sven Eckelmann wrote:
> The function batadv_nc_get_nc_node is responsible for adding new nc_nodes
> to the in_coding_list and out_coding_list. It first checks whether the
> entry already is in the list or not. If it is, then the creation of a new
> entry is aborted.
> 
> But the lock for the list is only held when the list is really modified.
> This could lead to duplicated entries because another context could create
> an entry with the same key between the check and the list manipulation.
> 
> The check and the manipulation of the list must therefore be in the same
> locked code section.
> 
> Fixes: 3ed7ada3f0bb ("batman-adv: network coding - detect coding nodes and
> remove these after timeout") Signed-off-by: Sven Eckelmann
> <sven@narfation.org>

Acked-by: Marek Lindner <mareklindner@neomailbox.ch>

Cheers,
Marek
diff mbox series

Patch

diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index c3578444..34caf129 100644
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -854,16 +854,27 @@  batadv_nc_get_nc_node(struct batadv_priv *bat_priv,
 	spinlock_t *lock; /* Used to lock list selected by "int in_coding" */
 	struct list_head *list;
 
+	/* Select ingoing or outgoing coding node */
+	if (in_coding) {
+		lock = &orig_neigh_node->in_coding_list_lock;
+		list = &orig_neigh_node->in_coding_list;
+	} else {
+		lock = &orig_neigh_node->out_coding_list_lock;
+		list = &orig_neigh_node->out_coding_list;
+	}
+
+	spin_lock_bh(lock);
+
 	/* Check if nc_node is already added */
 	nc_node = batadv_nc_find_nc_node(orig_node, orig_neigh_node, in_coding);
 
 	/* Node found */
 	if (nc_node)
-		return nc_node;
+		goto unlock;
 
 	nc_node = kzalloc(sizeof(*nc_node), GFP_ATOMIC);
 	if (!nc_node)
-		return NULL;
+		goto unlock;
 
 	/* Initialize nc_node */
 	INIT_LIST_HEAD(&nc_node->list);
@@ -872,22 +883,14 @@  batadv_nc_get_nc_node(struct batadv_priv *bat_priv,
 	kref_get(&orig_neigh_node->refcount);
 	nc_node->orig_node = orig_neigh_node;
 
-	/* Select ingoing or outgoing coding node */
-	if (in_coding) {
-		lock = &orig_neigh_node->in_coding_list_lock;
-		list = &orig_neigh_node->in_coding_list;
-	} else {
-		lock = &orig_neigh_node->out_coding_list_lock;
-		list = &orig_neigh_node->out_coding_list;
-	}
-
 	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_node %pM -> %pM\n",
 		   nc_node->addr, nc_node->orig_node->orig);
 
 	/* Add nc_node to orig_node */
-	spin_lock_bh(lock);
 	kref_get(&nc_node->refcount);
 	list_add_tail_rcu(&nc_node->list, list);
+
+unlock:
 	spin_unlock_bh(lock);
 
 	return nc_node;