linux-kernel - Re: [patch 2/3] vfio: make count unsigned to prevent integer underflow

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Date:	Thu, 28 Jun 2012 16:24:52 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch 2/3] vfio: make count unsigned to prevent integer
 underflow

On Thu, 2012-06-28 at 09:44 +0300, Dan Carpenter wrote:
> In vfio_pci_ioctl() there is a potential integer underflow where we
> might allocate less data than intended.  We check that hdr.count is not
> too large, but we don't check whether it is negative:
> 
> drivers/vfio/pci/vfio_pci.c
>    312          if (hdr.argsz - minsz < hdr.count * size ||
>    313              hdr.count > vfio_pci_get_irq_count(vdev, hdr.index))
>    314                  return -EINVAL;
>    315
>    316          data = kmalloc(hdr.count * size, GFP_KERNEL);
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> 
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 300d49b..86ef2da 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -347,7 +347,7 @@ struct vfio_irq_set {
>  #define VFIO_IRQ_SET_ACTION_TRIGGER	(1 << 5) /* Trigger interrupt */
>  	__u32	index;
>  	__s32	start;
> -	__s32	count;
> +	__u32	count;
>  	__u8	data[];
>  };
>  #define VFIO_DEVICE_SET_IRQS		_IO(VFIO_TYPE, VFIO_BASE + 10)

Good find.  I've actually trickled this through to change a number of
the function params to unsigned from int.  Also in this struct, start
should be unsigned.  Thanks for the report!

Alex

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