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Message-ID: <20180717173900.GA24627@embeddedor.com>
Date: Tue, 17 Jul 2018 12:39:00 -0500
From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
"Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] 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@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
drivers/vfio/pci/vfio_pci.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index b423a30..125b58e 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -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;
--
2.7.4
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