Posted on May 26, 2015 at 22:13Hello, in my earlier post I asked abouot buffer handling.
I investigated any further and found one potential error and one unused buffer.
1) buffer overflow
in file usbd_cdc_if.c
&sharpdefine APP_RX_DATA_SIZE 4
...
uint8_t UserRxBufferFS[APP_RX_DATA_SIZE];
...
static int8_t CDC_Init_FS(void)
{
...
USBD_CDC_SetRxBuffer(hUsbDevice_0, UserRxBufferFS);
...
}
@see USBD_CDC_SetRxBuffer doesn't take any length information
in file usbd_cdc.c this buffer is used in function:
static uint8_t USBD_CDC_Init (USBD_HandleTypeDef *pdev,
uint8_t cfgidx)
{
...
USBD_LL_PrepareReceive(pdev,
CDC_OUT_EP,
hcdc->RxBuffer,
CDC_DATA_HS_OUT_PACKET_SIZE);
...
}
So that means for safe operation the length of UserRxBufferFS must be minimum CDC_DATA_HS_OUT_PACKET_SIZE size.
2) unused buffer
in file usbd_cdc_if.c
&sharpdefine APP_TX_DATA_SIZE 4
...
uint8_t UserTxBufferFS[APP_TX_DATA_SIZE];
...
static int8_t CDC_Init_FS(void)
{
...
USBD_CDC_SetTxBuffer(hUsbDevice_0, UserTxBufferFS, 0);
...
}
This buffer is never used anywhere else.
The transmit code uses the buffer the user gives to the function.
The buffer UserTxBufferFS is not needed here and misleading.
Am I right?
Best regards, Adib.
#cdc #stm32f4 #usb #vcp
