Bluetooth: Fix public key callback management

Clear the callback list once generation is complete and we've done
calling all callbacks. This lets us use bt_pub_key_gen() multiple
times, which before this patch could have resulted in a corrupt linked
list.

Also remove redundant callback dispatching from bt_pub_key_gen() since
the function checks for the PUB_KEY_BUSY flag in the beginning, i.e.
there cannot be other pending generation actions at this point in the
code.

Signed-off-by: Johan Hedberg <[email protected]>

Author: Johan Hedberg

subsys/bluetooth/host/hci_core.c

@@ -3085,6 +3085,8 @@ static void le_pkey_complete(struct net_buf *buf)
 	for (cb = pub_key_cb; cb; cb = cb->_next) {
 		cb->func(evt->status ? NULL : evt->key);
 	}
+
+	pub_key_cb = NULL;
 }
 
 static void le_dhkey_complete(struct net_buf *buf)
@@ -5878,7 +5880,6 @@ u16_t bt_hci_get_cmd_opcode(struct net_buf *buf)
 #if defined(CONFIG_BT_ECC)
 int bt_pub_key_gen(struct bt_pub_key_cb *new_cb)
 {
-	struct bt_pub_key_cb *cb;
 	int err;
 
 	/*
@@ -5910,12 +5911,6 @@ int bt_pub_key_gen(struct bt_pub_key_cb *new_cb)
 		return err;
 	}
 
-	for (cb = pub_key_cb; cb; cb = cb->_next) {
-		if (cb != new_cb) {
-			cb->func(NULL);
-		}
-	}
-
 	return 0;
 }