This fixes the calculation of available buffer space in
bt_gatt_server_send_notification and sends pending notifications
immediately when there is no more room to add a notification.
Previously there was a buffer overflow caused by incorrect calculation
of available buffer space: data->offset can equal data->len
from a previous call to this function, leading
(data->len - data->offset) to underflow after data->offset += 2.
---
src/shared/gatt-server.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff --git a/src/shared/gatt-server.c b/src/shared/gatt-server.c
index 970c35f94..d53efe782 100644
--- a/src/shared/gatt-server.c
+++ b/src/shared/gatt-server.c
@@ -1700,20 +1700,35 @@ bool bt_gatt_server_send_notification(struct bt_gatt_server *server,
if (!server || (length && !value))
return false;
- if (multiple)
+ if (multiple) {
data = server->nfy_mult;
+ /* flush buffered data if this request hits buffer size limit */
+ if (data && data->offset > 0 &&
+ data->len - data->offset < 4 + length) {
+ if (server->nfy_mult->id)
+ timeout_remove(server->nfy_mult->id);
+ notify_multiple(server);
+ data = NULL;
+ }
+ }
+
if (!data) {
data = new0(struct nfy_mult_data, 1);
data->len = bt_att_get_mtu(server->att) - 1;
data->pdu = malloc(data->len);
}
+ if (multiple) {
+ if (data->len - data->offset < 4 + length)
+ return false;
+ } else {
+ if (data->len - data->offset < 2 + length)
+ return false;
+ }
+
put_le16(handle, data->pdu + data->offset);
data->offset += 2;
-
- length = MIN(data->len - data->offset, length);
-
if (multiple) {
put_le16(length, data->pdu + data->offset);
data->offset += 2;
--
2.25.1
