USBFS Bugfix

[Stefan Bader]

Chase Douglas wrote:
> Hi Markus,
> 
> On Wed, Mar 24, 2010 at 12:21 PM, Markus Rechberger
> <mrechberger at gmail.com> wrote:
>> Hi,
>>
>> on IRC I was recommended to submit this information to the mailinglist
>>
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/544527
> 
> The bug itself doesn't list much information. It basically says "usbfs
> is broken." We need some proof of what is going wrong, preferably
> something that can be tested when a fix is available.
> 
>> Here's a better solution.  In theory we could copy just the individual
>> packets from within the transfer buffer, but that would probably take
>> longer than simply copying the whole buffer.
>>
>> (This was a little hasty; I haven't even compile-tested the patch.
>> Some small fixes may be needed.)
> 
> The general procedure for fixes to reach Ubuntu is to have them sent
> upstream and be included in the mainline linux, and then to have the
> fix read the -stable tree. We then pull patches from the -stable tree
> for inclusion in Ubuntu.
> 
> If you can show that a specific patch has been found to fix an issue
> in Ubuntu and it has been accepted upstream by the maintainers of the
> kernel subsystem this impacts, we may be able to accept the patch as a
> pre-stable fix, in anticipation that it will be accepted into the
> -stable tree in the future.
> 
> What is the origin of this patch? Is it from upstream somewhere? A
> commit hash from linux-2.6 or some other tree would be very helpful.
> 
>> Alan Stern
>>
>>
>> -----------------------------------------------------------------------
>> This patch fixes a bug in the way isochronous input data is returned
>> to userspace for usbfs transfers.  The entire buffer must be copied,
>> not just the first actual_length bytes, because the individual packets
>> will be discontiguous if any of them are short.
>>
>> Signed-off-by: Alan Stern <stern at rowland.harvard.edu>
>> CC: stable <stable at kernel.org>
>>
>> ---
>> Index: usb-2.6/drivers/usb/core/devio.c
>> ===================================================================
>> --- usb-2.6.orig/drivers/usb/core/devio.c
>> +++ usb-2.6/drivers/usb/core/devio.c
>> @@ -1176,6 +1176,13 @@ static int proc_do_submiturb(struct dev_
>>                        free_async(as);
>>                        return -ENOMEM;
>>                }
>> +               /* Isochronous input data may end up being discontiguous
>> +                * if some of the packets are short.  Clear the buffer so
>> +                * that the gaps don't leak kernel data to userspace.
>> +                */
>> +               if (is_in && uurb->type == USBDEVFS_URB_TYPE_ISO)
>> +                       memset(as->urb->transfer_buffer, 0,
>> +                                       uurb->buffer_length);
>>        }
>>        as->urb->dev = ps->dev;
>>        as->urb->pipe = (uurb->type << 30) |
>> @@ -1312,10 +1319,14 @@ static int processcompl(struct async *as
>>        void __user *addr = as->userurb;
>>        unsigned int i;
>>
>> -       if (as->userbuffer && urb->actual_length)
>> -               if (copy_to_user(as->userbuffer, urb->transfer_buffer,
>> -                                urb->actual_length))
>> +       if (as->userbuffer && urb->actual_length) {
>> +               if (urb->number_of_packets > 0)         /* Isochronous */
>> +                       i = urb->transfer_buffer_length;
>> +               else                                    /* Non-Isoc */
>> +                       i = urb->actual_length;
>> +               if (copy_to_user(as->userbuffer, urb->transfer_buffer, i))
>>                        goto err_out;
>> +       }
>>        if (put_user(as->status, &userurb->status))
>>                goto err_out;
>>        if (put_user(urb->actual_length, &userurb->actual_length))
>>
>> It would be nice if this patch could go into the ubuntu lucid kernel
>> as soon as possible.
>>
>> Thanks,
>> Markus
> 
> -- Chase
> 
Well it seems to come from Alan Stern and be cc'ed to stable. So it should/would
come from there. But I have not seen it in the queue, yet. But it is in upstream:

commit 7152b592593b9d48b33f8997b1dfd6df9143f7ec
Author: Alan Stern <stern at rowland.harvard.edu>
Date:   Sat Mar 6 15:04:03 2010 -0500

    USB: fix usbfs regression