>From 8d95c1399e3ff345500a575e21254a73b0c89144 Mon Sep 17 00:00:00 2001 From: xmzyshypnc <1002992920@xxxxxx> Date: Fri, 16 Sep 2022 14:37:48 +0800 Subject: [PATCH] drm/i915/gvt: fix double-free bug in split_2MB_gtt_entry 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 only freeing spt in ppgtt_invalidate_spt in good case. Signed-off-by: xmzyshypnc <1002992920@xxxxxx> --- drivers/gpu/drm/i915/gvt/gtt.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c index 9f14fded8c0c..31d2a8d56384 100644 --- a/drivers/gpu/drm/i915/gvt/gtt.c +++ b/drivers/gpu/drm/i915/gvt/gtt.c @@ -959,7 +959,7 @@ static inline int ppgtt_put_spt(struct intel_vgpu_ppgtt_spt *spt) return atomic_dec_return(&spt->refcount); } -static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt); +static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *sptm, int is_error); static int ppgtt_invalidate_spt_by_shadow_entry(struct intel_vgpu *vgpu, struct intel_gvt_gtt_entry *e) @@ -995,7 +995,7 @@ static int ppgtt_invalidate_spt_by_shadow_entry(struct intel_vgpu *vgpu, ops->get_pfn(e)); return -ENXIO; } - return ppgtt_invalidate_spt(s); + return ppgtt_invalidate_spt(s, 0); } static inline void ppgtt_invalidate_pte(struct intel_vgpu_ppgtt_spt *spt, @@ -1016,7 +1016,7 @@ static inline void ppgtt_invalidate_pte(struct intel_vgpu_ppgtt_spt *spt, intel_gvt_dma_unmap_guest_page(vgpu, pfn << PAGE_SHIFT); } -static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt) +static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt, int is_error) { struct intel_vgpu *vgpu = spt->vgpu; struct intel_gvt_gtt_entry e; @@ -1059,9 +1059,11 @@ static int ppgtt_invalidate_spt(struct intel_vgpu_ppgtt_spt *spt) } } - trace_spt_change(spt->vgpu->id, "release", spt, + if (!is_error) { + trace_spt_change(spt->vgpu->id, "release", spt, spt->guest_page.gfn, spt->shadow_page.type); - ppgtt_free_spt(spt); + ppgtt_free_spt(spt); + } return 0; fail: gvt_vgpu_err("fail: shadow page %p shadow entry 0x%llx type %d\n", @@ -1215,7 +1217,7 @@ 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) { - ret = ppgtt_invalidate_spt(spt); + ret = ppgtt_invalidate_spt(spt, 1); return ret; } sub_se.val64 = se->val64; @@ -1393,7 +1395,7 @@ static int ppgtt_handle_guest_entry_removal(struct intel_vgpu_ppgtt_spt *spt, ret = -ENXIO; goto fail; } - ret = ppgtt_invalidate_spt(s); + ret = ppgtt_invalidate_spt(s, 0); if (ret) goto fail; } else { -- 2.25.1 Zheng Hacker <hackerzheng666@xxxxxxxxx> 于2022年9月8日周四 19:59写道: > > Hi Greg, > > I got it, Greg. > > Mid-Autumn Festival is coming and I will have a couple of days off. > I'll see what I can do after holiday :) > > Regards, > > Zheng Wang > > 在 2022年9月8日星期四,Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 写道: >> >> On Thu, Sep 08, 2022 at 05:09:40PM +0800, Zheng Hacker wrote: >> > Hi Zhenyu, >> > >> > This issue has been open for a few days. Could you plz write a patch >> > for that :) I'm not familiar with the logical code here. >> >> As this is only able to be hit in a theoretical system, it isn't that >> high of a priority, if any priority at all. Why not try to write a >> patch for it yourself to help resolve the issue faster? >> >> thanks, >> >> greg k-h