Re: [PATCH v3] [bug/urgent] dvb-usb-v2: Fix incorrect use of transfer_flags URB_FREE_BUFFER

On Mon, 2018-11-26 at 20:18 +0000, Malcolm Priestley wrote:

In commit 1a0c10ed7b media: dvb-usb-v2: stop using coherent memory for URBs incorrectly adds URB_FREE_BUFFER after every urb transfer.

It cannot use this flag because it reconfigures the URBs accordingly to suit connected devices. In doing a call to usb_free_urb is made and invertedly frees the buffers.

The stream buffer should remain constant while driver is up.

Signed-off-by: Malcolm Priestley tvboxspy@gmail.com CC: stable@vger.kernel.org # v4.18+

---

v3 change commit message to the actual cause

drivers/media/usb/dvb-usb-v2/usb_urb.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/media/usb/dvb-usb-v2/usb_urb.c b/drivers/media/usb/dvb-usb-v2/usb_urb.c index 024c751eb165..2ad2ddeaff51 100644 --- a/drivers/media/usb/dvb-usb-v2/usb_urb.c +++ b/drivers/media/usb/dvb-usb-v2/usb_urb.c @@ -155,7 +155,6 @@ static int usb_urb_alloc_bulk_urbs(struct usb_data_stream *stream) stream->props.u.bulk.buffersize, usb_urb_complete, stream);

• stream->urb_list[i]->transfer_flags = URB_FREE_BUFFER;
  

  stream->urbs_initialized++; } return 0;

@@ -186,7 +185,7 @@ static int usb_urb_alloc_isoc_urbs(struct usb_data_stream *stream) urb->complete = usb_urb_complete; urb->pipe = usb_rcvisocpipe(stream->udev, stream->props.endpoint);

• urb->transfer_flags = URB_ISO_ASAP | URB_FREE_BUFFER;
  

• urb->transfer_flags = URB_ISO_ASAP;
  

  urb->interval = stream->props.u.isoc.interval; urb->number_of_packets = stream-

...

props.u.isoc.framesperurb;

urb->transfer_buffer_length = stream-

...

props.u.isoc.framesize *

@@ -210,7 +209,7 @@ static int usb_free_stream_buffers(struct usb_data_stream *stream) if (stream->state & USB_STATE_URB_BUF) { while (stream->buf_num) { stream->buf_num--;

• 	stream->buf_list[stream->buf_num] = NULL;
  

• 	kfree(stream->buf_list[stream->buf_num]);
  

  } }

I have tested this against Arch Linux's kernel packages for both linux 4.20 and linux-lts 4.19.13. For both, the patch seems to fix the crashes I reported here: https://bugzilla.kernel.org/show_bug.cgi?id=201055

Thanks, Dan Ziemba