[PATCH 5.4 12/40] can: mcba_usb_start(): add missing urb->transfer_dma initialization

From: Greg Kroah-Hartman
Date: Mon Aug 02 2021 - 10:00:05 EST

From: Pavel Skripkin <paskripkin@xxxxxxxxx>

commit fc43fb69a7af92839551f99c1a96a37b77b3ae7a upstream.

Yasushi reported, that his Microchip CAN Analyzer stopped working
since commit 91c02557174b ("can: mcba_usb: fix memory leak in
mcba_usb"). The problem was in missing urb->transfer_dma

In my previous patch to this driver I refactored mcba_usb_start() code
to avoid leaking usb coherent buffers. To archive it, I passed local
stack variable to usb_alloc_coherent() and then saved it to private
array to correctly free all coherent buffers on ->close() call. But I
forgot to initialize urb->transfer_dma with variable passed to

All of this was causing device to not work, since dma addr 0 is not
valid and following log can be found on bug report page, which points
exactly to problem described above.

| DMAR: [DMA Write] Request device [00:14.0] PASID ffffffff fault addr 0 [fault reason 05] PTE Write access is not set

Fixes: 91c02557174b ("can: mcba_usb: fix memory leak in mcba_usb")
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=990850
Link: https://lore.kernel.org/r/20210725103630.23864-1-paskripkin@xxxxxxxxx
Cc: linux-stable <stable@xxxxxxxxxxxxxxx>
Reported-by: Yasushi SHOJI <yasushi.shoji@xxxxxxxxx>
Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
Tested-by: Yasushi SHOJI <yashi@xxxxxxxxxxxxxxx>
[mkl: fixed typos in commit message - thanks Yasushi SHOJI]
Signed-off-by: Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/net/can/usb/mcba_usb.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/net/can/usb/mcba_usb.c
+++ b/drivers/net/can/usb/mcba_usb.c
@@ -653,6 +653,8 @@ static int mcba_usb_start(struct mcba_pr

+ urb->transfer_dma = buf_dma;
usb_fill_bulk_urb(urb, priv->udev,
usb_rcvbulkpipe(priv->udev, MCBA_USB_EP_IN),