drm/i915/selftests: Change mock_request() to return error pointers

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: 52c0fdb ("drm/i915: Replace global breadcrumbs with per-context interrupt tracking")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/685c1417.050a0220.696f5.5c05@mx.google.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit 778fa8a)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Author: Dan Carpenter

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;
 	}
 

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;