On Tue, 2013-03-26 at 16:13 +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
> and thus smaller than "vdev->num_ctx" which is also a signed int.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> Static analysis stuff. Untested.
>
> This patch is not beautiful. There is probably a better limit to use if
> I knew the code.
>
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index acfcb1a..de54f69 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -371,6 +371,9 @@ static long vfio_pci_ioctl(void *device_data,
> hdr.count > vfio_pci_get_irq_count(vdev, hdr.index))
> return -EINVAL;
>
> + if (hdr.start > INT_MAX - hdr.count)
> + return -EINVAL;
> +
> data = memdup_user((void __user *)(arg + minsz),
> hdr.count * size);
> if (IS_ERR(data))
Thanks Dan. Is this more like what you're looking for?
commit 16deadb9d424c0af2162a5be2935fbc4e0f09b98
Author: Alex Williamson <alex.williamson@xxxxxxxxxx>
Date: Tue Mar 26 08:59:22 2013 -0600
vfio-pci: Fix possible integer overflow
The VFIO_DEVICE_SET_IRQS ioctl takes a start and count parameter, both
of which are unsigned. We attempt to bounds check these, but fail to
account for the case where start is a very large number, allowing
start + count to wrap back into the valid range. Bounds check both
start and start + count.
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index acfcb1a..866bde1 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -359,6 +359,7 @@ static long vfio_pci_ioctl(void *device_data,
if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
size_t size;
+ int max = vfio_pci_get_irq_count(vdev, hdr.index);
if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
size = sizeof(uint8_t);
@@ -368,7 +369,7 @@ static long vfio_pci_ioctl(void *device_data,
return -EINVAL;
if (hdr.argsz - minsz < hdr.count * size ||
- hdr.count > vfio_pci_get_irq_count(vdev, hdr.index))
+ hdr.start >= max || hdr.start + hdr.count > max)
return -EINVAL;
data = memdup_user((void __user *)(arg + minsz),
--
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