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usb: ensure RX buffers are a multiple of the packet size 

When performing an OUT transfer which is not a multiple of the
max packet size, the last packet of the OUT transfer should be
a short packet. However, there's no guarantee the host sends
the expected amount of data in the final packet.

The DWC2 USB controller handles this case by accepting any size
packet and copying it out to memory. So if the packet is bigger
than expected, it'll overrun the caller's buffer and Bad Things
will happen.

The USB 2.0 spec seems to endorse this behavior. Section 8.5.1
says "an ACK handshake indicates the endpoint has space for a
wMaxPacketSize data payload." So it is possible that other USB
controllers share the DWC2's behavior.

The simplest solution is to force all USB RX buffers to be big
enough to hold the transfer size, rounded up to a multiple of
the max packet size. For example, a transfer of 700 bytes would
require a 1024-byte buffer if the MPS = 512 bytes.

Change-Id: Ibb84d2b2d53aec8800a3a7c2449f7a17480acbcf
This commit is contained in:
Aidan MacDonald 2021-09-24 22:41:07 +01:00
parent a665c1faad
commit 24294bda15
3 changed files with 25 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
firmware/usbstack/usb_hid.c
View File

@ -666,8 +666,7 @@ void usb_hid_transfer_complete(int ep, int dir, int status, int length)
* to the DAP using the host's custom driver */
static int usb_hid_set_report(struct usb_ctrlrequest *req, void *reqdata)
{
static unsigned char buf[SET_REPORT_BUF_LEN] USB_DEVBSS_ATTR
__attribute__((aligned(32)));
static unsigned char buf[64] USB_DEVBSS_ATTR __attribute__((aligned(32)));
int length;
if ((req->wValue >> 8) != REPORT_TYPE_OUTPUT)

32
firmware/usbstack/usb_serial.c
View File

@ -174,7 +174,13 @@ static struct usb_endpoint_descriptor
.bInterval = 0
};
static struct cdc_line_coding line_coding;
union line_coding_buffer
{
struct cdc_line_coding data;
unsigned char raw[64];
};
static union line_coding_buffer line_coding USB_DEVBSS_ATTR;
/* send_buffer: local ring buffer.
* transit_buffer: used to store aligned data that will be sent by the USB
@ -184,10 +190,11 @@ static struct cdc_line_coding line_coding;
*/
#define BUFFER_SIZE 512
#define TRANSIT_BUFFER_SIZE 32
#define RECV_BUFFER_SIZE 32
static unsigned char send_buffer[BUFFER_SIZE];
static unsigned char transit_buffer[TRANSIT_BUFFER_SIZE]
USB_DEVBSS_ATTR __attribute__((aligned(4)));
static unsigned char receive_buffer[32]
static unsigned char receive_buffer[512]
USB_DEVBSS_ATTR __attribute__((aligned(32)));
static void sendout(void);
@ -293,13 +300,19 @@ bool usb_serial_control_request(struct usb_ctrlrequest* req, void* reqdata, unsi
{
if (req->bRequest == SET_LINE_CODING)
{
if (req->wLength == sizeof(line_coding))
if (req->wLength == sizeof(struct cdc_line_coding))
{
/* Receive line coding into local copy */
if(!reqdata)
usb_drv_control_response(USB_CONTROL_RECEIVE, &line_coding, sizeof(line_coding));
if (!reqdata)
{
usb_drv_control_response(USB_CONTROL_RECEIVE, line_coding.raw,
sizeof(struct cdc_line_coding));
}
else
{
usb_drv_control_response(USB_CONTROL_ACK, NULL, 0);
}
handled = true;
}
}
@ -317,10 +330,11 @@ bool usb_serial_control_request(struct usb_ctrlrequest* req, void* reqdata, unsi
{
if (req->bRequest == GET_LINE_CODING)
{
if (req->wLength == sizeof(line_coding))
if (req->wLength == sizeof(struct cdc_line_coding))
{
/* Send back line coding so host is happy */
usb_drv_control_response(USB_CONTROL_ACK, &line_coding, sizeof(line_coding));
usb_drv_control_response(USB_CONTROL_ACK, line_coding.raw,
sizeof(struct cdc_line_coding));
handled = true;
}
}
@ -332,7 +346,7 @@ bool usb_serial_control_request(struct usb_ctrlrequest* req, void* reqdata, unsi
void usb_serial_init_connection(void)
{
/* prime rx endpoint */
usb_drv_recv_nonblocking(ep_out, receive_buffer, sizeof receive_buffer);
usb_drv_recv_nonblocking(ep_out, receive_buffer, RECV_BUFFER_SIZE);
/* we come here too after a bus reset, so reset some data */
buffer_transitlength = 0;
@ -423,7 +437,7 @@ void usb_serial_transfer_complete(int ep,int dir, int status, int length)
/* Data received. TODO : Do something with it ? */
/* Get the next bit */
usb_drv_recv_nonblocking(ep_out, receive_buffer, sizeof receive_buffer);
usb_drv_recv_nonblocking(ep_out, receive_buffer, RECV_BUFFER_SIZE);
break;
case USB_DIR_IN:

2
firmware/usbstack/usb_storage.c
View File

@ -71,7 +71,7 @@
#endif /* USB_READ_BUFFER_SIZE */
/* We don't use sizeof() here, because we *need* a multiple of 32 */
#define MAX_CBW_SIZE 32
#define MAX_CBW_SIZE 512
#ifdef USB_WRITE_BUFFER_SIZE
#define WRITE_BUFFER_SIZE USB_WRITE_BUFFER_SIZE