4.17-stable review patch. If anyone has any objections, please let me know.
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From: Gustavo A. R. Silva gustavo@embeddedor.com
commit de5372da605d3bca46e3102bab51b7e1c0e0a6f6 upstream.
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
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: Zhenyu Wang zhenyuw@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/i915/gvt/kvmgt.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
--- 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"
@@ -1064,7 +1066,8 @@ static long intel_vgpu_ioctl(struct mdev } 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; @@ -1149,6 +1152,10 @@ static long intel_vgpu_ioctl(struct mdev 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;