On Thu, 2024-07-04 at 15:25 +0300, Pauli Virtanen wrote: > Hi, > > to, 2024-07-04 kello 12:24 +0200, Bastien Nocera kirjoitti: > > Set a lower-bound to the data MTU to avoid allocating -1 elements > > if > > bt_att_get_mtu() returns zero. > > > > Error: OVERRUN (CWE-119): [#def36] [important] > > bluez-5.76/src/shared/gatt-server.c:1121:2: zero_return: Function > > call "bt_att_get_mtu(server->att)" returns 0. > > bluez-5.76/src/shared/gatt-server.c:1121:2: assignment: Assigning: > > "data->mtu" = "bt_att_get_mtu(server->att)". The value of "data- > > >mtu" is now 0. > > bluez-5.76/src/shared/gatt-server.c:1123:19: assignment: Assigning: > > "__n" = "(size_t)(data->mtu - 1UL)". The value of "__n" is now > > 18446744073709551615. > > bluez-5.76/src/shared/gatt-server.c:1123:19: assignment: Assigning: > > "__s" = "1UL". > > bluez-5.76/src/shared/gatt-server.c:1123:19: overrun-buffer-arg: > > Calling "memset" with "__p" and "__n * __s" is suspicious because > > of the very large index, 18446744073709551615. The index may be due > > to a negative parameter being interpreted as unsigned. [Note: The > > source code implementation of the function has been overridden by a > > builtin model.] > > 1121| data->mtu = bt_att_get_mtu(server->att); > > 1122| data->length = 0; > > 1123|-> data->rsp_data = new0(uint8_t, data->mtu - 1); > > 1124| > > 1125| return data; > > --- > > src/shared/gatt-server.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/src/shared/gatt-server.c b/src/shared/gatt-server.c > > index 3a53d5dfde6b..c587553d655d 100644 > > --- a/src/shared/gatt-server.c > > +++ b/src/shared/gatt-server.c > > @@ -1118,7 +1118,7 @@ static struct read_mult_data > > *read_mult_data_new(struct bt_gatt_server *server, > > data->server = server; > > data->num_handles = num_handles; > > data->cur_handle = 0; > > - data->mtu = bt_att_get_mtu(server->att); > > + data->mtu = MAX(bt_att_get_mtu(server->att), > > BT_ATT_DEFAULT_LE_MTU); > > Is this correct, probably MTU less than default are valid? This is the same code as in bt_gatt_server_new(). > > > data->length = 0; > > data->rsp_data = new0(uint8_t, data->mtu - 1); > > > > Might be better to instead: MAX(data->mtu, 1) - 1 I'd be fine with either, if somebody knows that particular part of the code better than I do...
