[PATCH 4.14 backport] drm/i915/gvt: Fix mmap range check

[Zhenyu Wang <zhenyuw@linux.intel.com>]

This is to fix missed mmap range check on vGPU bar2 region
and only allow to map vGPU allocated GMADDR range, which means
user space should support sparse mmap to get proper offset for
mmap vGPU aperture. And this takes care of actual pgoff in mmap
request as original code always does from beginning of vGPU
aperture.

Fixes: 659643f7d814 ("drm/i915/gvt/kvmgt: add vfio/mdev support to KVMGT")
Cc: "Monroy, Rodrigo Axel" <rodrigo.axel.monroy@intel.com>
Cc: "Orrala Contreras, Alfredo" <alfredo.orrala.contreras@intel.com>
Cc: stable@vger.kernel.org # v4.10+
Reviewed-by: Hang Yuan <hang.yuan@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
---
Note: This is backported version of upstream
commit 51b00d8509dc ("drm/i915/gvt: Fix mmap range check") for 4.14.x stable.
---
 drivers/gpu/drm/i915/gvt/kvmgt.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index 73c672fc17c4..9834b7c1c9d4 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -807,11 +807,18 @@ static ssize_t intel_vgpu_write(struct mdev_device *mdev,
 	return -EFAULT;
 }
 
+static inline bool intel_vgpu_in_aperture(struct intel_vgpu *vgpu,
+					  unsigned long off)
+{
+	return off >= vgpu_aperture_offset(vgpu) &&
+		off < vgpu_aperture_offset(vgpu) + vgpu_aperture_sz(vgpu);
+}
+
 static int intel_vgpu_mmap(struct mdev_device *mdev, struct vm_area_struct *vma)
 {
 	unsigned int index;
 	u64 virtaddr;
-	unsigned long req_size, pgoff = 0;
+	unsigned long req_size, pgoff, req_start;
 	pgprot_t pg_prot;
 	struct intel_vgpu *vgpu = mdev_get_drvdata(mdev);
 
@@ -829,7 +836,17 @@ static int intel_vgpu_mmap(struct mdev_device *mdev, struct vm_area_struct *vma)
 	pg_prot = vma->vm_page_prot;
 	virtaddr = vma->vm_start;
 	req_size = vma->vm_end - vma->vm_start;
-	pgoff = vgpu_aperture_pa_base(vgpu) >> PAGE_SHIFT;
+	pgoff = vma->vm_pgoff &
+		((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+	req_start = pgoff << PAGE_SHIFT;
+
+	if (!intel_vgpu_in_aperture(vgpu, req_start))
+		return -EINVAL;
+	if (req_start + req_size >
+	    vgpu_aperture_offset(vgpu) + vgpu_aperture_sz(vgpu))
+		return -EINVAL;
+
+	pgoff = (gvt_aperture_pa_base(vgpu->gvt) >> PAGE_SHIFT) + pgoff;
 
 	return remap_pfn_range(vma, virtaddr, pgoff, req_size, pg_prot);
 }
-- 
2.20.1