Am Donnerstag, den 15.08.2019, 12:41 +0100 schrieb Jonathan Bell: > On Thu, Aug 15, 2019 at 11:55 AM Oliver Neukum <oneukum@xxxxxxxx> wrote: > > > > Am Mittwoch, den 14.08.2019, 16:59 +0100 schrieb Jonathan Bell: > > > As reported by one of our users here: > > > https://github.com/raspberrypi/linux/issues/3148 > > > > > > There is a bug when the dwc2 core receives USB data packets that are > > > between 1 and 4 bytes in length - 4 bytes are always written to memory > > > where the non-packet bytes are garbage. > > > > Hi, > > > > in which function does that happen? If your buffer cannot handle 4 > > bytes I cannot see how it copes with teh DMA rules. > > > > In drivers/media/usb/uvc/uvc_ctrl.c:uvc_ctrl_populate_cache() and friends. OK, I see. > The UVC driver passes in offsets into a struct uvc_control as the > "buffer" that usb_control_msg() fills. Not quite that bad. It passes a pointer into the middle of a buffer used at different offsets for the transfer. This is technically allowed as long as you never touch the buffer while a transfer is ongoing. That is an accident waiting to happen. Please make a patch using a bounce buffer allocated with knalloc() in drivers/media/usb/uvc/uvc_ctrl.c:uvc_ctrl_populate_cache() and friends. Regards Oliver
