Re: [patch] vfio-pci: integer overflow in vfio_pci_ioctl()

[Dan Carpenter <dan.carpenter@oracle.com>]

On Tue, Mar 26, 2013 at 04:13:58PM +0300, Dan Carpenter wrote:
> The worry here is that a large value of hdr.start would cause a
> read before the start of the array and a crash in
> vfio_msi_set_vector_signal().
> 
> The check in vfio_msi_set_block() is not enough:
> 
> 	if (start + count > vdev->num_ctx)
> 		return -EINVAL;
> 
> A large value of "start" would lead to an integer overflow.
> 
> The check in vfio_msi_set_vector_signal() doesn't work either:
> 
> 	if (vector >= vdev->num_ctx)
> 		return -EINVAL;
> 
> Here "vector" is "count" casted to a signed int so it would be negative
                    ^^^^^
I meant "start" not "count".

> and thus smaller than "vdev->num_ctx" which is also a signed int.
> 

Gar...  I hate this patch already.  I really should make
vdev->num_ctx an unsigned int.  I'll send that in a v2 along with
whatever other suggestions people send.

regards,
dan carpenter