Re: [PATCH 2/2] uio: new driver to support PCI MSI-X

[Vlad Zolotarov <vladz@cloudius-systems.com>]

On 10/06/15 01:49, Michael S. Tsirkin wrote:
> On Tue, Oct 06, 2015 at 01:09:55AM +0300, Vladislav Zolotarov wrote:
>> How about instead of trying to invent the wheel just go and attack the problem
>> directly just like i've proposed already a few times in the last days: instead
>> of limiting the UIO limit the users that are allowed to use UIO to privileged
>> users only (e.g. root). This would solve all clearly unresolvable issues u are
>> raising here all together, wouldn't it?
> No - root or no root, if the user can modify the addresses in the MSI-X
> table and make the chip corrupt random memory, this is IMHO a non-starter.

Michael, how this or any other related patch is related to the problem u 
r describing? The above ability is there for years and if memory serves 
me well it was u who wrote uio_pci_generic with this "security flaw".  ;)

This patch in general only adds the ability to receive notifications per 
MSI-X interrupt and it has nothing to do with the ability to reprogram 
the MSI-X related registers from the user space which was always there.

>
> And tainting kernel is not a solution - your patch adds a pile of
> code that either goes completely unused or taints the kernel.
> Not just that - it's a dedicated userspace API that either
> goes completely unused or taints the kernel.
>
>>> --
>>> MST