Re: dvb shared datastructure bug?

From: Manu Abraham
Date: Tue Feb 13 2007 - 06:14:45 EST


On 2/13/07, Marcel Siegert <mws@xxxxxxxxxxx> wrote:
On Tuesday 13 February 2007, Arjan van de Ven wrote:
> Hi,
>
> while working on the last pieces of the file_ops constantification, DVB
> is the small village in France that is holding the Romans at bay... but
> I think I found the final flaw in it now:
>
> *pdvbdev = dvbdev = kmalloc(sizeof(struct dvb_device), GFP_KERNEL);
>
> if (!dvbdev) {
> mutex_unlock(&dvbdev_register_lock);
> return -ENOMEM;
> }
>
> memcpy(dvbdev, template, sizeof(struct dvb_device));
> dvbdev->type = type;
> dvbdev->id = id;
> dvbdev->adapter = adap;
> dvbdev->priv = priv;
>
> dvbdev->fops->owner = adap->module;
>
>
> this is the place in DVB that is writing to a struct file_operations.
> But as with almost all such cases in the kernel, this one is buggy:
> While the code nicely copies a template dvbdev, that template only has a
> pointer to a *shared* fops struct, the copy doesn't help that. So this
> code is overwriting the fops owner field for ALL active devices, not
> just the ones the copy of the template is for....
>
> I'm lost in the maze of this part of DVB (it seems to have some magic
> potion to resist me) but I was hoping some of the local citizens could
> take a look at this buglet...
>
> Greetings,
> Arjan van de Ven

hi arjan,
thanks for pointing out this issue.

attached find a patch that fixes the problem.

@mauro - please pull changeset a7ac92d208fe
dvbdev: fix illegal re-usage of fileoperations struct

from http://www.linuxtv.org/hg/~mws/v4l-dvb-fixtree


Ack'd-by: Manu Abraham <manu@xxxxxxxxxxx>
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