Re: [Intel-gfx] [PATCH 1/3] drm/i915: Do not access rq->engine without a reference

[Matthew Brost <matthew.brost@intel.com>]

On Wed, Jun 15, 2022 at 12:13:46AM +0530, Ramalingam C wrote:
> From: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> 
> In i915_fence_get_driver_name(), user may not hold a
> reference to rq->engine. Hence do not access it. Instead,
> store required device private pointer in 'rq->i915' and use it.
> 
> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
> Suggested-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  drivers/gpu/drm/i915/i915_request.c | 3 ++-
>  drivers/gpu/drm/i915/i915_request.h | 2 ++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 73d5195146b0..7f6998bf390c 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -60,7 +60,7 @@ static struct kmem_cache *slab_execute_cbs;
>  
>  static const char *i915_fence_get_driver_name(struct dma_fence *fence)
>  {
> -	return dev_name(to_request(fence)->engine->i915->drm.dev);
> +	return dev_name(to_request(fence)->i915->drm.dev);
>  }
>  
>  static const char *i915_fence_get_timeline_name(struct dma_fence *fence)
> @@ -937,6 +937,7 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
>  	rq->engine = ce->engine;
>  	rq->ring = ce->ring;
>  	rq->execution_mask = ce->engine->mask;
> +	rq->i915 = ce->engine->i915;
>  
>  	ret = intel_timeline_get_seqno(tl, rq, &seqno);
>  	if (ret)
> diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
> index 28b1f9db5487..47041ec68df8 100644
> --- a/drivers/gpu/drm/i915/i915_request.h
> +++ b/drivers/gpu/drm/i915/i915_request.h
> @@ -196,6 +196,8 @@ struct i915_request {
>  	struct dma_fence fence;
>  	spinlock_t lock;
>  
> +	struct drm_i915_private *i915;
> +
>  	/**
>  	 * Context and ring buffer related to this request
>  	 * Contexts are refcounted, so when this request is associated with a
> -- 
> 2.20.1
>