[PATCH 4.4 41/53] can: peak: fix potential bug in packet fragmentation

Greg Kroah-Hartman
2018-01-22T08:40:33Z

From: Stephane Grosjean <s.grosjean@peak-system.com>

commit d8a243af1a68395e07ac85384a2740d4134c67f4 upstream.

In some rare conditions when running one PEAK USB-FD interface over
a non high-speed USB controller, one useless USB fragment might be sent.
This patch fixes the way a USB command is fragmented when its length is
greater than 64 bytes and when the underlying USB controller is not a
high-speed one.

Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/can/usb/peak_usb/pcan_usb_fd.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

--- a/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb_fd.c
@@ -184,7 +184,7 @@ static int pcan_usb_fd_send_cmd(struct p
void *cmd_head = pcan_usb_fd_cmd_buffer(dev);
int err = 0;
u8 *packet_ptr;
- int i, n = 1, packet_len;
+ int packet_len;
ptrdiff_t cmd_len;

/* usb device unregistered? */
@@ -201,17 +201,13 @@ static int pcan_usb_fd_send_cmd(struct p
}

packet_ptr = cmd_head;
+ packet_len = cmd_len;

/* firmware is not able to re-assemble 512 bytes buffer in full-speed */
- if ((dev->udev->speed != USB_SPEED_HIGH) &&
- (cmd_len > PCAN_UFD_LOSPD_PKT_SIZE)) {
- packet_len = PCAN_UFD_LOSPD_PKT_SIZE;
- n += cmd_len / packet_len;
- } else {
- packet_len = cmd_len;
- }
+ if (unlikely(dev->udev->speed != USB_SPEED_HIGH))
+ packet_len = min(packet_len, PCAN_UFD_LOSPD_PKT_SIZE);

- for (i = 0; i < n; i++) {
+ do {
err = usb_bulk_msg(dev->udev,
usb_sndbulkpipe(dev->udev,
PCAN_USBPRO_EP_CMDOUT),
@@ -224,7 +220,12 @@ static int pcan_usb_fd_send_cmd(struct p
}

packet_ptr += packet_len;
- }
+ cmd_len -= packet_len;
+
+ if (cmd_len < PCAN_UFD_LOSPD_PKT_SIZE)
+ packet_len = cmd_len;
+
+ } while (packet_len > 0);

return err;
}