linux-kernel - Re: [PATCH v2] drm/i915/selftests: Change mock

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Message-ID: <aFw0VyNuV5twrHIQ@intel.com>
Date: Wed, 25 Jun 2025 13:39:35 -0400
From: Rodrigo Vivi <rodrigo.vivi@...el.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
CC: Jani Nikula <jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, "Frederic
 Weisbecker" <frederic@...nel.org>, Chris Wilson <chris@...is-wilson.co.uk>,
	<intel-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
	<linux-kernel@...r.kernel.org>, <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH v2] drm/i915/selftests: Change mock_request() to return
 error pointers

On Wed, Jun 25, 2025 at 10:21:58AM -0500, Dan Carpenter wrote:
> There was an error pointer vs NULL bug in __igt_breadcrumbs_smoketest().
> The __mock_request_alloc() function implements the
> smoketest->request_alloc() function pointer.  It was supposed to return
> error pointers, but it propogates the NULL return from mock_request()
> so in the event of a failure, it would lead to a NULL pointer
> dereference.
> 
> To fix this, change the mock_request() function to return error pointers
> and update all the callers to expect that.
> 
> Fixes: 52c0fdb25c7c ("drm/i915: Replace global breadcrumbs with per-context interrupt tracking")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
> V2: In v1 I just updated __mock_request_alloc() to return an error pointer
>     but in v2, I changed mock_request() to update an error pointer and
>     updated all the callers.  It's a more extensive change, but hopefully
>     cleaner.

Thank you

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@...el.com>


> 
>  drivers/gpu/drm/i915/selftests/i915_request.c | 20 +++++++++----------
>  drivers/gpu/drm/i915/selftests/mock_request.c |  2 +-
>  2 files changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/selftests/i915_request.c b/drivers/gpu/drm/i915/selftests/i915_request.c
> index 88870844b5bd..2fb7a9e7efec 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_request.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_request.c
> @@ -73,8 +73,8 @@ static int igt_add_request(void *arg)
>  	/* Basic preliminary test to create a request and let it loose! */
>  
>  	request = mock_request(rcs0(i915)->kernel_context, HZ / 10);
> -	if (!request)
> -		return -ENOMEM;
> +	if (IS_ERR(request))
> +		return PTR_ERR(request);
>  
>  	i915_request_add(request);
>  
> @@ -91,8 +91,8 @@ static int igt_wait_request(void *arg)
>  	/* Submit a request, then wait upon it */
>  
>  	request = mock_request(rcs0(i915)->kernel_context, T);
> -	if (!request)
> -		return -ENOMEM;
> +	if (IS_ERR(request))
> +		return PTR_ERR(request);
>  
>  	i915_request_get(request);
>  
> @@ -160,8 +160,8 @@ static int igt_fence_wait(void *arg)
>  	/* Submit a request, treat it as a fence and wait upon it */
>  
>  	request = mock_request(rcs0(i915)->kernel_context, T);
> -	if (!request)
> -		return -ENOMEM;
> +	if (IS_ERR(request))
> +		return PTR_ERR(request);
>  
>  	if (dma_fence_wait_timeout(&request->fence, false, T) != -ETIME) {
>  		pr_err("fence wait success before submit (expected timeout)!\n");
> @@ -219,8 +219,8 @@ static int igt_request_rewind(void *arg)
>  	GEM_BUG_ON(IS_ERR(ce));
>  	request = mock_request(ce, 2 * HZ);
>  	intel_context_put(ce);
> -	if (!request) {
> -		err = -ENOMEM;
> +	if (IS_ERR(request)) {
> +		err = PTR_ERR(request);
>  		goto err_context_0;
>  	}
>  
> @@ -237,8 +237,8 @@ static int igt_request_rewind(void *arg)
>  	GEM_BUG_ON(IS_ERR(ce));
>  	vip = mock_request(ce, 0);
>  	intel_context_put(ce);
> -	if (!vip) {
> -		err = -ENOMEM;
> +	if (IS_ERR(vip)) {
> +		err = PTR_ERR(vip);
>  		goto err_context_1;
>  	}
>  
> diff --git a/drivers/gpu/drm/i915/selftests/mock_request.c b/drivers/gpu/drm/i915/selftests/mock_request.c
> index 09f747228dff..1b0cf073e964 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_request.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_request.c
> @@ -35,7 +35,7 @@ mock_request(struct intel_context *ce, unsigned long delay)
>  	/* NB the i915->requests slab cache is enlarged to fit mock_request */
>  	request = intel_context_create_request(ce);
>  	if (IS_ERR(request))
> -		return NULL;
> +		return request;
>  
>  	request->mock.delay = delay;
>  	return request;
> -- 
> 2.47.2
>