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

[Andi Shyti]

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.

Andi

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