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    SubjectRe: Flaws with "UIO: Add the User IO core code" (with patch)
    Date
    Am Samstag 28 April 2007 01:19 schrieb Alan Cox:
    > > +static ssize_t uio_read(struct file *filep, char __user *buf,
    > > + size_t count, loff_t *ppos)
    > > +{
    > > + struct uio_listener *listener = filep->private_data;
    > > + struct uio_device *idev = listener->dev;
    > > + DECLARE_WAITQUEUE(wait, current);
    > > + ssize_t retval;
    > > + int event_count;
    > > +
    > > + if (idev->info->irq == UIO_IRQ_NONE)
    > > + return -EIO;
    > > +
    > > + if (count != sizeof(int))
    > > + return -EINVAL;
    >
    > AFAIK we don't currently have any platform that runs binaries with
    > different sizes of "int" but this is a) an unsigned value anyway, and b)
    > should be a fixed type (eg u32)

    I reviewed the code once more and find it OK. There is only one legal
    value for the parameter "count" of uio_read(), and that's sizeof(int).
    The data that is actually read is the element "event" of struct uio_device,
    which is of type atomic_t. The latter has the size of an int.

    Unfortunately, the fact that the read count _must_ be sizeof(int) is not
    mentioned in the documentation. I'll send a patch for that ASAP.

    >
    > Otherwise it looks ok at the momenmt, although there is a real nasty
    > waiting for anyone who tries to use it. At the point open is possible or
    > IRQs can be enabled you are safe in the core merged as idev->info is
    > always valid, but any driver module trying to go back via info->uio_dev
    > has a NULL pointer for an early IRQ or open event.

    This patch should fix it:


    Index: linux-2.6.22-rc/drivers/uio/uio.c
    ===================================================================
    --- linux-2.6.22-rc.orig/drivers/uio/uio.c 2007-04-28 20:01:02.000000000 +0200
    +++ linux-2.6.22-rc/drivers/uio/uio.c 2007-04-28 20:15:00.000000000 +0200
    @@ -633,6 +633,8 @@
    if (ret)
    goto err_uio_dev_add_attributes;

    + info->uio_dev = idev;
    +
    if (idev->info->irq >= 0) {
    ret = request_irq(idev->info->irq, uio_interrupt,
    idev->info->irq_flags, idev->info->name, idev);
    @@ -640,7 +642,6 @@
    goto err_request_irq;
    }

    - info->uio_dev = idev;
    return 0;

    err_request_irq:

    Thanks for your review,
    Hans

    -
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