Re: [PATCH] drm/i915: Fix potential spectre vulnerability

[Kunwu Chan]

Hi Tvrtko,
Thank you very much for your kind suggestion, I have modified it in 
accordance with your suggestion.

On 2023/11/2 19:32, Tvrtko Ursulin wrote:
> On 02/11/2023 10:16, chentao wrote:
> > Fix smatch warning:
> > drivers/gpu/drm/i915/gem/i915_gem_context.c:847 set_proto_ctx_sseu()
> > warn: potential spectre issue 'pc->user_engines' [r] (local cap)
> >
> > Signed-off-by: chentao <chentao@xxxxxxxxxx>
>
> I don't know if this is actually exploitable given the time deltas 
> between the index is read from userspace and acted upon here, which is 
> at least two ioctls apart. But I suppose no harm in fixing and for 
> safety so we need to add:
>
> Fixes: d4433c7600f7 ("drm/i915/gem: Use the proto-context to handle 
> create parameters (v5)")
> Cc: <stable@xxxxxxxxxxxxxxx> # v5.15+
>
> > ---
> >   drivers/gpu/drm/i915/gem/i915_gem_context.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c 
> > b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index 9a9ff84c90d7..b2fdfc7ca4de 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -843,7 +843,7 @@ static int set_proto_ctx_sseu(struct 
> > drm_i915_file_private *fpriv,
> >           if (idx >= pc->num_user_engines)
> >               return -EINVAL;
> > -
>
> Just please refrain from random whitespace modifications like this blank 
> line removal. If you resend without that you can add my r-b.
>
> Regards,
>
> Tvrtko
>
> > +        idx = array_index_nospec(idx, pc->num_user_engines);
> >           pe = &pc->user_engines[idx];
> >           /* Only render engine supports RPCS configuration. */