Re: [PATCH] drm/i915: Prevent potential UAF in engine_init_common

[Nirmoy Das <nirmoy.das@xxxxxxxxx>]

On 10/11/2023 2:20 PM, Jani Nikula wrote:
> On Wed, 11 Oct 2023, Nirmoy Das <nirmoy.das@xxxxxxxxx> wrote:
> > If measure_breadcrumb_dw() returns an error and bce isn't created,
> > this commit ensures that intel_engine_destroy_pinned_context()
> > is not called with a NULL bce.
> So it's a potential NULL pointer dereference, not use after free like
> the subject says. Please fix the subject.

ah right. I will resend.


Thanks,

Nirmoy

> BR,
> Jani.
>
>
> > Fixes: b35274993680 ("drm/i915: Create a kernel context for GGTT updates")
> > Cc: Oak Zeng <oak.zeng@xxxxxxxxx>
> > Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
> > Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_engine_cs.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > index 179d9546865b..4a11219e560e 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > @@ -1491,7 +1491,8 @@ static int engine_init_common(struct intel_engine_cs *engine)
> >   	return 0;
> >   
> >   err_bce_context:
> > -	intel_engine_destroy_pinned_context(bce);
> > +	if (bce)
> > +		intel_engine_destroy_pinned_context(bce);
> >   err_ce_context:
> >   	intel_engine_destroy_pinned_context(ce);
> >   	return ret;