drm/i915/gvt: fix double free bug in split_2MB_gtt_entry

If intel_gvt_dma_map_guest_page failed, it will call
ppgtt_invalidate_spt, which will finally free the spt.
But the caller function ppgtt_populate_spt_by_guest_entry
does not notice that, it will free spt again in its error
path.

Fix this by canceling the mapping of DMA address and freeing sub_spt.
Besides, leave the handle of spt destroy to caller function instead
of callee function when error occurs.

Fixes: b901b252b6cf ("drm/i915/gvt: Add 2M huge gtt support")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20221229165641.1192455-1-zyytlz.wz@163.com

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index 6b40390..4ec8530 100644 (file)
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -1209,10 +1209,8 @@ static int split_2MB_gtt_entry(struct intel_vgpu *vgpu,
        for_each_shadow_entry(sub_spt, &sub_se, sub_index) {
                ret = intel_gvt_dma_map_guest_page(vgpu, start_gfn + sub_index,
                                                   PAGE_SIZE, &dma_addr);
-               if (ret) {
-                       ppgtt_invalidate_spt(spt);
-                       return ret;
-               }
+               if (ret)
+                       goto err;
                sub_se.val64 = se->val64;
 
                /* Copy the PAT field from PDE. */
@@ -1231,6 +1229,17 @@ static int split_2MB_gtt_entry(struct intel_vgpu *vgpu,
        ops->set_pfn(se, sub_spt->shadow_page.mfn);
        ppgtt_set_shadow_entry(spt, se, index);
        return 0;
+err:
+       /* Cancel the existing addess mappings of DMA addr. */
+       for_each_present_shadow_entry(sub_spt, &sub_se, sub_index) {
+               gvt_vdbg_mm("invalidate 4K entry\n");
+               ppgtt_invalidate_pte(sub_spt, &sub_se);
+       }
+       /* Release the new allocated spt. */
+       trace_spt_change(sub_spt->vgpu->id, "release", sub_spt,
+               sub_spt->guest_page.gfn, sub_spt->shadow_page.type);
+       ppgtt_free_spt(sub_spt);
+       return ret;
 }
 
 static int split_64KB_gtt_entry(struct intel_vgpu *vgpu,