On 2018.08.02 22:40:19 -0500, Gustavo A. R. Silva wrote:

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/gpu/drm/i915/gvt/kvmgt.c:1232 intel_vgpu_ioctl() warn: potential spectre issue 'vgpu->vdev.region' [r]

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

Thanks for catching this! Applied.

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

---

drivers/gpu/drm/i915/gvt/kvmgt.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index 4d2f53a..b703f20 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -43,6 +43,8 @@ #include <linux/mdev.h> #include <linux/debugfs.h>

+#include <linux/nospec.h>

#include "i915_drv.h" #include "gvt.h"

@@ -1139,7 +1141,8 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd, } else if (cmd == VFIO_DEVICE_GET_REGION_INFO) { struct vfio_region_info info; struct vfio_info_cap caps = { .buf = NULL, .size = 0 };

• int i, ret;
  

• unsigned int i;
  

• int ret;
  

  struct vfio_region_info_cap_sparse_mmap *sparse = NULL; size_t size; int nr_areas = 1;

@@ -1224,6 +1227,10 @@ static long intel_vgpu_ioctl(struct mdev_device *mdev, unsigned int cmd, if (info.index >= VFIO_PCI_NUM_REGIONS + vgpu->vdev.num_regions) return -EINVAL;

• 		info.index =
  

• 			array_index_nospec(info.index,
  

• 					VFIO_PCI_NUM_REGIONS +
  

• 					vgpu->vdev.num_regions);
  
  	i = info.index - VFIO_PCI_NUM_REGIONS;
  
  

-- 2.7.4

---

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