On Mon, Sep 05, 2022 at 03:46:09PM +0800, Zheng Hacker wrote:
> I rewrote the letter. Hope it works.
>
> There is a double-free security bug in split_2MB_gtt_entry.
>
> Here is a calling chain :
> ppgtt_populate_spt->ppgtt_populate_shadow_entry->split_2MB_gtt_entry.
> If intel_gvt_dma_map_guest_page failed, it will call
> ppgtt_invalidate_spt, which will finally call ppgtt_free_spt and
> kfree(spt). But the caller does not notice that, and it will call
> ppgtt_free_spt again in error path.
>
> Fix this by returning the result of ppgtt_invalidate_spt to split_2MB_gtt_entry.
>
> Signed-off-by: Zheng Wang
>
> ---
> drivers/gpu/drm/i915/gvt/gtt.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
> index ce0eb03709c3..9f14fded8c0c 100644
> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> @@ -1215,7 +1215,7 @@ static int split_2MB_gtt_entry(struct intel_vgpu *vgpu,
> ret = intel_gvt_dma_map_guest_page(vgpu, start_gfn + sub_index,
> PAGE_SIZE, &dma_addr);
> if (ret) {
> - ppgtt_invalidate_spt(spt);
> + ret = ppgtt_invalidate_spt(spt);
> return ret;
But now you just lost the original error, shouldn't this succeed even if
intel_gvt_dma_map_guest_page() failed?
And how are you causing intel_gvt_dma_map_guest_page() to fail in a real
system?
thanks,
greg k-h
