Re: [PATCH v2] drm/i915: Fix potential spectre vulnerability

[Tvrtko Ursulin]

On 06/11/2023 09:57, Andi Shyti wrote:
> Hi Kunwu,
>
> On Fri, Nov 03, 2023 at 10:32:57AM +0800, Kunwu Chan 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)
> >
> > Fixes: d4433c7600f7 ("drm/i915/gem: Use the proto-context to handle create parameters (v5)")
> > Cc: <stable@xxxxxxxxxxxxxxx> # v5.15+
> > Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
> > Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > Link: https://lore.kernel.org/all/20231102101642.52988-1-chentao@xxxxxxxxxx
> > ---
> >   drivers/gpu/drm/i915/gem/i915_gem_context.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > index 9a9ff84c90d7..e38f06a6e56e 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> > @@ -844,6 +844,7 @@ static int set_proto_ctx_sseu(struct drm_i915_file_private *fpriv,
> >   		if (idx >= pc->num_user_engines)
> >   			return -EINVAL;
> >   
> > +		idx = array_index_nospec(idx, pc->num_user_engines);
>
> you ignored my comment, though.

Sorry it was me, I considered it fine as is given it is the same pattern 
as elsewhere in the file. I've merged the patch btw.

Regards,

Tvrtko

> Andi
>
> >   		pe = &pc->user_engines[idx];
> >   
> >   		/* Only render engine supports RPCS configuration. */
> > --
> > 2.34.1