[PATCH v3 5/6] drm/i915/gvt: Assign NULL to the pointer after memory free.

[Zhenyu Wang]

On 2019.04.29 12:22:06 +0000, Gimbitskii, Aleksei wrote:
> Thanks for the reminding and sorry that I forget to mention that.  But we think that if we add this error message here, probably we also need to add the error message in other similar places, which seems a bit over too much. How about we still follow the existing style?
>

Then instead of use-after-free, just remove that error message,
and provide cleaner error message in future if helpful.

> -----Original Message-----
> From: Xu, Colin 
> Sent: Thursday, April 25, 2019 8:32 AM
> To: Gimbitskii, Aleksei <aleksei.gimbitskii at intel.com>
> Cc: Zhenyu Wang <zhenyuw at linux.intel.com>; intel-gvt-dev at lists.freedesktop.org; Wang, Zhi A <zhi.a.wang at intel.com>
> Subject: Re: [PATCH v3 5/6] drm/i915/gvt: Assign NULL to the pointer after memory free.
> 
> 
> On 2019-04-25 11:14, Zhenyu Wang wrote:
> > On 2019.04.23 15:04:12 +0300, Aleksei Gimbitskii wrote:
> >> The klocwork static code analyzer complains about using pointer after 
> >> being freed, because further we pass it to the gvt_vgpu_err() function.
> >> Assign pointer to be NULL intentionaly, to meet requirements of the 
> >> code analyzer.
> >>
> >> This patch fixed the issue #648 reported as error by klocwork.
> >>
> >> Signed-off-by: Aleksei Gimbitskii <aleksei.gimbitskii at intel.com>
> >> Cc: Zhenyu Wang <zhenyuw at linux.intel.com>
> >> Cc: Zhi Wang <zhi.a.wang at intel.com>
> >> ---
> >>   drivers/gpu/drm/i915/gvt/gtt.c | 1 +
> >>   1 file changed, 1 insertion(+)
> >>
> >> diff --git a/drivers/gpu/drm/i915/gvt/gtt.c 
> >> b/drivers/gpu/drm/i915/gvt/gtt.c index 061499a38f4d..927753a59a1e 
> >> 100644
> >> --- a/drivers/gpu/drm/i915/gvt/gtt.c
> >> +++ b/drivers/gpu/drm/i915/gvt/gtt.c
> >> @@ -1106,6 +1106,7 @@ static struct intel_vgpu_ppgtt_spt 
> >> *ppgtt_populate_spt_by_guest_entry(
> >>   
> >>   err_free_spt:
> >>   	ppgtt_free_spt(spt);
> >> +	spt = NULL;
> >>   err:
> >>   	gvt_vgpu_err("fail: shadow page %p guest entry 0x%llx type %d\n",
> >>   		     spt, we->val64, we->type);
> > I think we can remove this error message which doesn't tell the reason 
> > to fail at all, but have err message in earlier path where we can 
> > indicate the reason.
> 
> Seem like miss my comment in v2.
> 
> I would suggest add different msg before the two "goto err_free_spt",
> 
> then in this err_free_stp label you could just return without print the
> 
> same msg as err. Otherwise you can't tell the reason from the same err.
> 
> >
> > _______________________________________________
> > intel-gvt-dev mailing list
> > intel-gvt-dev at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev
> 
> --
> Best Regards,
> Colin Xu
> 

-- 
Open Source Technology Center, Intel ltd.

$gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/intel-gvt-dev/attachments/20190430/677fe7cb/attachment.sig>