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vfio/pci: Fix potential Spectre v1 

info.index can be indirectly controlled by user-space, hence leading
to a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

drivers/vfio/pci/vfio_pci.c:734 vfio_pci_ioctl()
warn: potential spectre issue 'vdev->region'

Fix this by sanitizing info.index before indirectly using it to index
vdev->region

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2

Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Gustavo A. R. Silva 2018-07-17 12:39:00 -05:00 committed by Alex Williamson
parent 9d3cce1e8b
commit 0e714d2778
1 changed files with 4 additions and 0 deletions
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4
drivers/vfio/pci/vfio_pci.c
View File

@ -28,6 +28,7 @@
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include <linux/vgaarb.h>
#include <linux/nospec.h>
#include "vfio_pci_private.h"
@ -727,6 +728,9 @@ static long vfio_pci_ioctl(void *device_data,
if (info.index >=
VFIO_PCI_NUM_REGIONS + vdev->num_regions)
return -EINVAL;
info.index = array_index_nospec(info.index,
VFIO_PCI_NUM_REGIONS +
vdev->num_regions);
i = info.index - VFIO_PCI_NUM_REGIONS;