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

[Jani Nikula]

On Wed, 11 Oct 2023, Nirmoy Das <nirmoy.das at intel.com> 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.

BR,
Jani.


>
> Fixes: b35274993680 ("drm/i915: Create a kernel context for GGTT updates")
> Cc: Oak Zeng <oak.zeng at intel.com>
> Cc: Andi Shyti <andi.shyti at linux.intel.com>
> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
> ---
>  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;

-- 
Jani Nikula, Intel