USBFS Bugfix

Chase Douglas chase.douglas at canonical.com
Wed Mar 24 16:44:09 UTC 2010


On Wed, Mar 24, 2010 at 12:39 PM, Stefan Bader
<stefan.bader at canonical.com> wrote:
> 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

Ahh, I didn't realize Alan is the maintainer of the code. I'll leave
it up to you, Stefan, to determine how to handle this.

-- Chase




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